Advertisement

Rubella virus infections and immune status among pregnant women before the introduction of rubella vaccine in Amhara Regional State, Ethiopia

Open AccessPublished:August 27, 2018DOI:https://doi.org/10.1016/j.ijid.2018.07.024

      Highlights

      • About 9.5% (95% CI 7.3–11.7%) of the pregnant women had acute/recent rubella infections at the time of data collection.
      • 79.5% (95% CI 76.3–82.5%) of the study participants were immune to rubella virus infection as a result of prior natural/wild rubella infections.
      • 11.0% (95% CI 8.7–13.7) of the pregnant women showed no evidence of protective antibodies against rubella virus and represent the susceptible group; these women might be at risk of developing rubella-associated anomalies in their future pregnancies.
      • Introducing rubella-containing vaccine and screening all women of child-bearing age before conception and during pregnancy might be important to minimize rubella-associated health complications in the country.

      Abstract

      Background

      Rubella and its associated congenital anomalies have been greatly reduced in most developed countries through use of the rubella vaccine. However, the magnitude of the problem is underestimated and there are no well-established rubella/congenital rubella syndrome prevention and control strategies in many developing countries, including Ethiopia. The aim of this study was to determine the prevalence of rubella virus infections among pregnant women and their immune status before the introduction of rubella vaccine in Amhara Regional State, Ethiopia.

      Methods

      A prospective cross-sectional study was conducted among pregnant women in Dessie, Felege-Hiwot, and University of Gondar referral hospitals, from December 2015 to February 2017. After obtaining written informed consent, socio-demographic data, reproductive history, clinical manifestations, and the possible risk factors for rubella virus infections were collected using a structured questionnaire. The laboratory analysis of rubella-specific antibodies was done using an enzyme-linked immunoassay method on venous blood samples. Data were entered and analyzed using IBM SPSS Statistics version 20. Binary logistic regression was used to determine the strength of association between the dependent variables and covariates.

      Results

      A total of 600 pregnant women were included in the study. Their mean age was 26.4 ± 5 years (range 16–40 years). The overall seroprevalence of rubella infection was 89%. Of the total study participants, 9.5% were positive for rubella-specific IgM antibody, which indicates acute/recent rubella virus infection. In contrast, 79.5% of them had protective levels of rubella-specific IgG antibody and were immune as a result of previous wild-type rubella infection. However, 11% of the pregnant women were negative for both rubella-specific antibodies; these women represent the susceptible group.

      Conclusions

      A large number of pregnant women had acute/recent rubella virus infections at the time of data collection, indicating that the virus is endemic in the study area. More than a tenth of pregnant women were found to be susceptible to acquiring the infection in future pregnancies, with the possible risk of rubella-associated congenital anomalies. Hence screening of all women of child-bearing age before conception and during pregnancy might reduce the devastating effects of the virus on the developing fetus.

      Keywords

      Introduction

      Rubella virus is an important human pathogen that causes an acute and contagious disease known as rubella, little red, 3-day measles, or German measles (
      • Fokunang C.N.
      • Chia J.
      • Ndumbe P.
      • Mbu P.
      • Atashili J.
      Clinical studies on seroprevalence of rubella virus in pregnant women of Cameroon regions.
      ). Humans are the only reservoir for this virus (
      • Mounerou S.
      • Maléwé K.
      • Anoumou D.Y.
      • Sami N.
      • Koffi A.
      • Mireille P.
      Seroprevalence of rubella IgG antibody among pregnant women attending antenatal clinic in Lomé, Togo.
      ). The virus has an incubation period of 2–3 weeks. The route of transmission is air-borne in postnatal cases and transplacental during pregnancy (
      • Kolawole O.M.
      • Anjori E.O.
      • Adekanle D.A.
      • Kolawole C.F.
      • Durowade K.A.
      Seroprevalence of rubella IgG antibody in pregnant women in Osogbo, Nigeria.
      ). The disease caused by this virus commonly occurs in childhood and is characterized by a maculopapular rash associated with a low-grade fever, lymphadenopathy, and malaise (
      • Al-Rubai B.
      • Aboud M.
      • Hamza W.
      Evaluation of anti- rubella antibodies among childbearing age women in Babylon Governorate.
      ). It can also cause joint pains, headache, and conjunctivitis in adults (
      • Lezan M.M.
      Prevalence of rubella virus in pregnant women in Kirkuk City-Iraq.
      ). Transient arthralgia or arthritis may also occur (
      • Heggie A.D.
      • Robbins F.C.
      Natural rubella acquired after birth: clinical features and complications.
      ). It is also a rare cause of thrombocytopenic purpura and encephalitis (
      • Sherman F.E.
      • Michaels R.H.
      • Kenny F.M.
      Acute encephalopathy (encephalitis) complicating rubella: report of cases with virologic studies, cortisol-production determinations, and observations at autopsy.
      ). However, up to 50% of rubella cases are subclinical (
      • Horstmann D.M.
      • Riordan J.T.
      • Ohtawara M.
      • Niederman J.C.
      A natural epidemic of rubella in a closed population: virological and epidemiological observations.
      ).
      Rubella infection is considered relatively benign, and in the absence of pregnancy, the infection is usually mild and self-limiting (
      • CDC
      Control and prevention of rubella: evaluation and management of suspected outbreaks, rubella in pregnant women, and surveillance for congenital rubella syndrome.
      ). However, during pregnancy, it has a devastating effect on the developing fetus (
      • Adam O.
      • Makkawi T.
      • Kannan A.
      • Osman M.E.
      Seroprevalence of rubella among pregnant women in Khartoum state, Sudan.
      ,
      • Cradock-Watson J.E.
      • Ridehalg M.K.S.
      • Anderson M.J.
      • Pattison J.R.
      Outcome of asymptomatic infection with rubella virus during pregnancy.
      ) and this represents a major health concern worldwide (
      • Mirambo Mariam M.
      • Majigo Mtebe
      • Aboud Said
      • Groß Uwe
      • Mshana Stephen E.
      Serological makers of rubella infection in Africa in the pre vaccination era: a systematic review.
      ). Currently, there is no specific treatment for the virus (
      • Olajide Okikiola
      • Aminu Maryam
      • Randawa Abdullahi J.
      • Adejo Daniel S.
      Seroprevalence of rubella-specific IgM and IgG antibodies among pregnant women seen in a tertiary hospital in Nigeria.
      ). However, its burden can be minimized through use of the live attenuated rubella vaccine (
      • Alleman Mary M.
      • Wannemuehler Kathleen A.
      • Hao Lijuan
      • Perelyginab Ludmila
      • Icenogle Joseph P.
      • Vynnycky Emilia
      • et al.
      Estimating the burden of rubella virus infection and congenital rubella syndrome through a rubella immunity assessment among pregnant women in the Democratic Republic of the Congo: potential impact on vaccination policy.
      ,
      • Demicheli V.
      • Debalini M.G.
      • Di Pietrantonj C.
      Vaccines for measles, mumps and rubella in children.
      ,
      • WHO
      Eliminating measles and rubella. Framework for the verification process in the WHO European Region.
      ). The control of rubella and congenital rubella syndrome (CRS) relies on a high population level of immunity (
      • Gilbert Nicolas L.
      • Rotondo Jenny
      • Shapiro Janna
      • Sherrard Lindsey
      • Fraser William D.
      • Ward Brian J.
      Seroprevalence of rubella antibodies and determinants of susceptibility to rubella in a cohort of pregnant women in Canada, 2008–2011.
      ).
      The World Health Organization (WHO) proposed the introduction of rubella vaccine in each country in the year 2000 (
      • Robertson S.E.
      • Featherstone D.A.
      • Gacic-Dobo M.
      • Hersh B.S.
      Rubella and congenital rubella syndrome: global update.
      ) and different efforts are undergoing in different WHO regions (
      • Martínez-Quintana E.
      • Castillo-Solórzano C.
      • Torner N.
      • Rodríguez-González F.
      Congenital rubella syndrome: a matter of concern.
      ,
      • CDC
      Progress toward control of rubella and prevention of congenital rubella syndrome worldwide, 2009.
      ,
      • WHO
      Progress towards eliminating rubella and congenital rubella syndrome in the western hemisphere, 2003-2008.
      ). As a result, the burden has declined, although mostly in industrialized countries (
      • Adewumi Olubusuyi M.
      • Olayinka Adebowale O.
      • Olusola Babatunde A.
      • Faleye Temitope O.C.
      • Sule Waidi F.
      • Adesina Olubukola
      Epidemiological evaluation of rubella virus infection among pregnant women in Ibadan, Nigeria.
      ). However, rubella vaccine is still not available in many developing countries (
      • Njeru Ian
      • Onyango Dickens
      • Ajack Yusuf
      • Kiptoo Elizabeth
      Rubella outbreak in a Rural Kenyan District, 2014: documenting the need for routine rubella immunization in Kenya.
      ) and it is not included in their immunization programs (
      • WHO
      Global measles and rubella strategic plan: 2012-2020.
      ). Rubella is an under-recognized public health problem (
      • Cutts F.T.
      • Vynnycky E.
      Modelling the incidence of congenital rubella syndrome in developing countries.
      ,
      • Mamvura Tafadzwa Shepherd
      • Chin’ombe Nyasha
      • Ruhanya Vurayai
      • Nziramasanga Pasipanodya
      Seroprevalence of Rubella Virus IgG in pregnant women in Harare, Zimbabwe.
      ). In Africa, few countries have included rubella vaccine in their national immunization programs and data on the seroprevalence of the virus are very limited (
      • Martínez-Quintana E.
      • Castillo-Solórzano C.
      • Torner N.
      • Rodríguez-González F.
      Congenital rubella syndrome: a matter of concern.
      ).
      Although Ethiopia has planned to introduce the rubella vaccine (
      • WHO
      Ethiopia | Immunization.
      ), it is currently not included in the national immunization program (
      • Getahun Mekonen
      • Beyene Berhane
      • Gallagher Kathleen
      • Ademe Ayesheshem
      • Teshome Birke
      • Tefera Mesfin
      • et al.
      Epidemiology of rubella virus cases in the pre-vaccination era of Ethiopia, 2009–2015.
      ). There are only a few reports on rubella in the country (
      • Cutts F.T.
      • Abebe A.
      • Messele T.
      • Dejene A.
      • Enquselassie F.
      • Nigatu W.
      • et al.
      Sero-epidemiology of rubella in the urban population of Addis Ababa, Ethiopia.
      ,
      • Gebreselassie Lakew
      • Almaz Abebe
      The immune status of young adult females in Ethiopia to rubella virus infection.
      ), with most containing very old information (
      • Gebreselassie Lakew
      • Almaz Abebe
      The immune status of young adult females in Ethiopia to rubella virus infection.
      ,
      • Sandow D.
      • Okubagzhi G.S.
      • Arnold U.
      • Denkmann N.
      Seroepidemiological study on rubella in pregnant women in Gondar Region, Northern Ethiopia.
      ) or reporting on suspected cases of measles among children (
      • Mitiku Kassahun
      • Bedada Tesfaye
      • Masresha Balcha
      • Kegne Wendemagegn
      • Nafo-Traore Fatoumata
      • Tesfaye Neghist
      • et al.
      The epidemiology of rubella disease in ethiopia: data from the measles case-based surveillance system.
      ,
      • Getahun Mekonen
      • Beyene Berhane
      • Gallagher Kathleen
      • Ademe Ayesheshem
      • Teshome Birke
      • Tefera Mesfin
      • et al.
      Epidemiology of rubella virus cases in the pre-vaccination era of Ethiopia, 2009–2015.
      ,
      • Shiferaw Dejenie
      • Birke Teklu
      • Esete Teshome
      • Ayenachew Assefa
      • Ketema BekeleHiwot
      • Beyene Berhane
      The epidemiology of laboratory confirmed rubella cases in Oromia Region, Ethiopia, 2010–2015: data from the measles case-based surveillance system.
      ). There is only one recently published report on rubella among pregnant women (
      • Tamirat Biniam
      • Hussen Techalew
      • Shimelis Siraj
      Rubella virus infection and associated factors among pregnant women attending the antenatal care clinics of public hospitals in Hawassa City, Southern Ethiopia: a crosssectional study.
      ) and one case report on CRS (
      • Mekonnen Demeke
      Clinically confirmed congenital rubella syndrome: the role of echocardiography.
      ) in the country. All of these indicate that there is scarcity of data and that the magnitude of rubella and its consequences is largely unknown. Hence, the aim of this study was to determine rubella virus infections and immune status among pregnant women before the introduction of rubella vaccine in Amhara Regional State, Ethiopia.

      Materials and methods

      Study design, area, and period

      A prospective cross-sectional study was conducted in three referral hospitals in Amhara Regional State, namely Dessie, Felege-Hiwot, and University of Gondar referral hospitals, from December 2015 to February 2017.

      Study participants

      The study participants were pregnant women who visited the respective antenatal care clinics of the referral hospitals during the study period and gave informed consent and the required amount of blood sample for laboratory analysis.

      Sample size and sampling technique

      The study participants were selected using a simple random sampling technique and the sample size was calculated using a single population proportion formula by considering a 95% confidence interval, 4% margin of error, and 50% proportion. The sample size was proportionally allocated to the selected referral hospitals based on the previous flow of pregnant women visiting the antenatal care clinics of the respective referral hospitals. Pregnant women who gave informed consent and the required amount of blood sample were included in the study. Pregnant women who were seriously sick at the time of data collection and those who visited the respective referral hospitals for the second time during the study period were excluded from the study.

      Data collection

      After obtaining written informed consent from each study participant, socio-demographic data, clinical information, and information on reproductive history and possible risk factors of the pregnant women were collected using a structured and pre-tested questionnaire.

      Blood collection and handling

      Using a plain tube, 5 ml of venous blood was collected aseptically from each pregnant woman for the determination of rubella antibodies. Blood was allowed to clot for an hour at room temperature, centrifuged at 3500 rpm for 5 min, and then serum was separated and collected in sterile storage vials to be stored at −70 °C until laboratory analysis.

      Laboratory analysis and interpretation of results

      Rubella IgM and IgG antibodies were determined using an enzyme-linked immunoassay (ELIA) method as per the manufacturer’s instructions (Linear Chemicals SL, Spain). The results were read in a micro-well reader at 450 nm and compared in a parallel manner with calibrators and controls. For rubella-specific IgM, the qualitative result was interpreted as positive if the rubella IgM index was >1.1, negative when the index was <0.9, and equivocal when the index was ≥0.9 and ≤1.1. The quantitative rubella IgG result was expressed in international units per milliliter (IU/ml). In accordance with the manufacturer’s instructions, the IgG result was interpreted as positive when the IgG index value was >10 IU/ml, as equivocal at 5–10 IU/ml, and as negative at <5 IU/ml.

      Quality assurance mechanisms

      The rubella test kits (IgM and IgG EIA kits) have their own quality control materials that can be run in parallel with patient samples, and all test procedures were done strictly following the manufacturer’s instructions. In addition, standard operational procedures were strictly followed and the questionnaire was pre-tested in non-selected health institutions. Training was given for data collectors and they were also regularly supervised by the research team. In addition, the inclusion and exclusion criteria were given to the data collectors.

      Data analysis procedure

      Data were checked for completeness, cleaned manually, and entered into and analyzed using IBM SPSS Statistics version 20.0 (IBM Corp., Armonk, NY, USA). Data were summarized using frequency tables and graphs. For continuous variables, the range and mean ± standard deviation (SD) were used. In the case of two categorical variables, univariate and multivariate analysis with a 95% confidence interval (CI) was performed to measure the association, and p-value of less than 0.05 was considered statistically significant.

      Results

      Socio-demographic characteristics of the pregnant women

      A total of 600 pregnant women were included in the study. The mean age of the participants was 26.4 ± 5 years (range 16–40 years). Approximately a third of the study participants were in the age group of 25–29 years (n = 224, 37.3%), the majority were married (n = 587, 97.8%), and approximately two-thirds lived in an urban area (n = 386, 64.3%). One hundred and seventy (28.3%) of the study participants had a certificate and above level of education and 317 (53.0%) had an occupation of housewife (Table 1).
      Table 1Rubella-specific IgM and IgG antibodies in relation to socio-demographic characteristics and trimesters of pregnancy of women in Amhara Regional State referral hospitals, Ethiopia, December 2015 to February 2017.
      Socio-demographic characteristicsNumber testedIgM-positiveOnly IgG-positive
      Positive, n (%)COR (95% CI)p-ValuePositive, n (%)COR (95% CI)p-Value
      Age group
       <20 years303 (10.0)120 (66.7)1
       20–24 years18613 (7.0)0.7 (0.18–2.53)0.561149 (80.1)2.0 (0.87–4.67)0.103
       25–29 years22422 (9.8)1.0 (0.28–3.50)0.975178 (79.5)1.9 (0.85–4.42)0.117
       30–34 years9811 (11.2)1.1 (0.30–4.4)0.85179 (80.6)2.1 (0.84–5.16)0.115
       ≥35 years628 (12.9)1.3 (0.33–5.43)0.68851 (82.3)2.3 (0.85–6.30)0.100
      Marital status
       Married58755 (9.4)1468 (79.7)2.6 (0.43–15.87)0.294
       Single81 (12.5)1.4 (0.17–11.44)0.7646 (75.0)2.0 (0.18–22.06)0.571
       Divorced51 (20.0)2.4 (0.27–22.02)0.4333 (60.0)1
      Residence
       Urban38644 (11.4)2.0 (1.05–3.78)0.036313 (81.1)1.3 (0.87–1.96)0.196
       Rural21413 (6.1)1164 (76.6)1
      Educational status
       No formal education14614 (9.6)1.2 (0.54–2.57)0.673120 (82.2)1.0 (0.58–1.83)0.922
       Elementary school11811 (9.3)1.2 (0.50–2.62)0.74793 (78.8)0.8 (0.46–1.50)0.534
       High school16618 (10.8)1.4 (0.65–2.82)0.417125 (75.3)0.7 (0.40–1.15)0.150
       Certificate and above17014 (8.2)1139 (81.8)1
      Occupation
       Civil servant13513 (9.6)1.3 (0.28–6.27)0.717105 (77.8)1.2 (0.47–3.17)0.676
       Merchant676 (9.0)1.2 (0.23–6.51)0.80859 (88.1)2.6 (0.83–8.02)0.101
       Farmer351 (2.9)0.4 (0.03–4.28)0.42431 (88.6)2.7 (0.70–10.47)0.148
       Student191 (5.3)0.7 (0.06–8.26)0.77317 (89.5)3.0 (0.54–16.27)0.209
       Housewife31734 (10.7)1.5 (0.34–6.62)0.591245 (77.3)1.2 (0.48–2.93)0.703
       Daily laborer272 (9.1)120 (74.0)1
      COR, crude odds ratio; CI, confidence interval.

      Overall prevalence of rubella IgM and IgG antibodies

      The overall seroprevalence of rubella was 89.0% (n = 534) (95% CI 86.3–91.3%). Of the total study participants, 49 (8.2%, 95% CI 6.2–10.2%) were positive for both IgM and IgG antibodies at the same time. However, eight (1.3%, 95% CI 0.5–2.2%) of the pregnant women were positive only for rubella IgM antibodies and 477 (79.5%, 95% CI 76.3–82.5%) were positive only for rubella IgG antibodies. This indicates that the overall number of rubella-specific IgM-positive pregnant women at the time of data collection was 57 (9.5%, 95% CI 7.3–11.7%). According to the present study, 66 (11.0%, 95% CI 8.7–13.7%) of the pregnant women were negative for both rubella IgM and IgG antibodies; these women represent the susceptible group (Figure 1).
      Figure 1
      Figure 1The overall prevalence of rubella specific IgM and IgG antibodies among pregnant women in Amhara Regional Sate Referral Hospitals, Ethiopia, December 2015-February 2017. The letter “A”: indicates the number of pregnant women who were positive for both rubella specific IgM and IgG antibodies at a time, “B”: Positive only for rubella IgM antibody, “C”: Positive only for rubella IgG antibody, “D”: Negative for both rubella IgM and IgG antibodies.

      Rubella IgM and IgG antibodies in relation to socio-demographic characteristics

      In the present study, eight (12.9%) of the IgM-positive study participants were in the age group of ≥35 years (p = 0.688), one (20.0%) was divorced (p = 0.433), 18 (10.8%) had a high school level of educational attainment (p = 0.417), and 34 (10.7%) had an occupation of housewife (p = 0.591). Similarly, 51 (82.3%) of the IgG-positive pregnant women were in the age group of ≥35 years (p = 0.100), 468 (79.7%) were married (p = 0.294), 313 (81.1%) lived in an urban area (p = 0.196), 17 (89.5%) had an occupation of student (p = 0.209), and 120 (82.2%) had no formal education (p = 0.922). There was no significant association for any of these socio-demographic factors. However, the pregnant women living in urban settings had IgM positivity two times (95% CI 1.05–3.78) that of the women living in rural settings (p = 0.036) (Table 1).

      Rubella IgM and IgG antibodies in relation to reproductive characteristics

      At the time of data collection, 211 (35.2%) of the women were in the first trimester of pregnancy, 191 (31.8%) in the second trimester, and 198 (33.0%) in the third trimester. With regard to the relationship of rubella antibodies with the study participants’ reproductive characteristics, 26 (13.1%) of the IgM-positive pregnant women were in the third trimester of their current pregnancy (p = 0.136). In addition, six (17.1%) of the IgM-positive study participants had a previous history of more than three live births (p = 0.191), one (33.3%) had a previous history of more than three still births (p = 0.205), and six were grand multigravidae (16.2%) (p = 0.175) (Table 2).
      Table 2Rubella IgM and IgG antibodies in relation to the reproductive history of the pregnant women in Amhara Regional State referral hospitals, Ethiopia, December 2015 to February 2017.
      Reproductive characteristicsNumber testedIgM-positiveOnly IgG-positive
      Positive, n (%)COR (95% CI)p-ValuePositive, n (%)COR (95% CI)p-Value
      Trimester at the time of data collection
       First trimester21118 (8.5)1174 (82.5)1.5 (0.93–2.44)0.096
       Second trimester19113 (6.8)0.8 (0.37–1.64)0.518153 (80.1)1.3 (0.80–2.10)0.302
       Third trimester19826 (13.1)1.6 (0.86–3.10)0.136150 (75.8)1
      History of live births
       None25625 (9.8)1197 (77.0)1
       1–330926 (8.4)0.9 (0.48–1.51)0.577251 (81.2)1.3 (0.86–1.95)0.212
       >3356 (17.1)1.9 (0.72–5.05)0.19129 (83.0)1.5 (0.57–3.65)0.434
      History of spontaneous abortion
       None51041 (8.0)1413 (81.0)1.7 (1.04–2.87)0.034
       1–39016 (17.8)2.5 (1.32–4.63)0.00564 (71.1)1
      History of stillbirth
       None54952 (9.5)1435 (79.2)1.9 (0.17–21.23)0.599
       1–3484 (8.3)0.9 (0.30–2.52)0.79540 (83.3)2.5 (0.20–31.0)0.434
       >331 (33.3)4. 8 (0.43–53.6)0.2052 (66.7)1
      Having malformed children
       None57655 (9.5)1.2 (0.27–5.07)0.842459 (79.7)1.3 (0.51–3.37)0.578
       1–3242 (8.3)118 (75.0)1
      Gravidity
       Primigravida25623 (9.0)1200 (78.1)1
       Multigravida30728 (9.1)1.0 (0.57–1.83)0.955248 (80.8)1.18 (0.78–1.77)0.346
       Grand multigravida376 (16.2)1.96 (0.74–5.19)0.17529 (78.4)1.0 (0.44–2.34)0.972
      COR, crude odds ratio; CI, confidence interval.
      One hundred and seventy-four (82.5%) of the IgG-positive women were in the third trimester of their current pregnancy (p = 0.096), 29 (83.0%) had a history of more than three previous live births (p = 0.972), 40 (83.3%) had a history of one to three still births (p = 0.434), and 248 (80.8%) were multigravidae (p = 0.346). None of these reproductive history factors was significantly associated with IgM and IgG positivity. However, the pregnant women with a history of one to three previous spontaneous abortions had 2.5 times (95% CI 1.32–4.63) the IgM positivity of those without a history of spontaneous abortion (p = 0.005). In contrast, pregnant women without a previous history of spontaneous abortion had 1.7 times (95% CI 1.04–2.87) the IgG positivity rate of those who had a previous history of spontaneous abortion (p = 0.034) (Table 2).

      Rubella IgM and IgG antibodies in relation to the clinical manifestations

      In this study, four (26.7%) of the IgM-positive pregnant women had lymphadenopathy (p = 0.082), four (14.3%) had a runny nose (p = 0.381), and six (17.1%) had a sore throat (p = 0.119) at the time of data collection. In addition, 19 (12.2%) had a headache (p = 0.187), five (20.8%) had an inflamed eye (p = 0.062), and three (17.6%) had jaundice (p = 0.255). In contrast, 471 (79.8%) of the IgG-positive pregnant women had no arthralgia/arthritis (p = 0.138) and 467 (79.8%) had no lymphadenopathy (p = 0.124). In addition, 458 (80.1%) of the IgG-positive pregnant women had no runny/stuffy nose (p = 0.124) and 403 (80.9%) had no malaise (p = 0.058). Furthermore, 361 (81.3%) of the IgG-positive pregnant women had no headache (p = 0.066) and 465 (79.8%) had no jaundice (p = 0.360). However, none of them had significant association (Table 3).
      Table 3Rubella IgM and IgG antibodies in relation to the clinical information of the pregnant women in Amhara Regional State referral hospitals, Ethiopia, December 2015 to February 2017.
      Clinical informationNumber testedIgM-positiveOnly IgG-positive
      Positive, n (%)COR (95% CI)AOR (95% CI)p-ValuePositive, n (%)COR (95% CI)AOR (95% CI)p-Value
      Mild fever
       Yes16211 (6.8)1130 (80.2)1.1 (0.68–1.67)
       No43846 (10.5)1.6 (0.81–3.19)347 (79.2)1
      Maculopapular rash
       Yes308 (26.7)3.9 (1.64–9.14)
      Significant association (p<0.05).
      3.5 (1.46–8.65)0.00517 (56.7)10.026
       No57049 (8.6)1460 (80.7)3.2 (1.51–6.78)
      Significant association (p<0.05).
      2.5 (1.12–5.69)
      Arthralgia/arthritis
       Yes101 (10.0)1.1 (0.13–8.52)6 (60.0)1
       No59056 (9.5)1471 (79.8)2.6 (0.73–9.50)
      Lymphadenopathy
       Yes154 (26.7)3.7 (1.12–11.86)
      Significant association (p<0.05).
      3.0 (0.87–10.1)0.08210 (66.7)1
       No58553 (9.1)1467 (79.8)2.0 (0.66–5.90)
      Runny or stuffy nose
       Yes284 (14.3)1.6 (0.55–4.88)19 (67.9)1
       No57253 (9.3)1458 (80.1)1.9 (0.84–4.32)
      Sore throat
       Yes356 (17.1)2.1 (0.83–5.26)23 (65.7)10.315
       No56551 (9.0)1454 (80.4)2.1 (1.03–4.42)
      Significant association (p<0.05).
      1.5 (0.68–3.33)
      General malaise
       Yes10210 (9.8)1.0 (0.51–2.14)74 (72.5)1
       No49847 (9.4)1403 (80.9)1.6 (0.98–2.62)
      Headache
       Yes15619 (12.2)1.5 (0.83–2.67)116 (74.4)1
       No44438 (8.6)1361 (81.3)1.5 (0.97–2.31)
      Inflamed/red eyes
       Yes245 (20.8)2.7 (0.95–7.40)15 (62.5)10.170
       No57652 (9.0)1462 (80.2)2.4 (1.04–5.70)
      Significant association (p<0.05).
      1.9 (0.77–4.58)
      Jaundice
       Yes173 (17.6)2.1 (0.59–7.54)12 (70.6)1
       No58354 (9.3)1465 (79.8)1.6 (0.57–4.75)
      COR, crude odds ratio; AOR, adjusted odds ratio; CI, confidence interval.
      a Significant association (p < 0.05).
      There was a significant association between the presence of a maculopapular rash and rubella-specific IgM positivity in the multivariate logistic regression analysis. The pregnant women with a maculopapular rash had 3.5 times (95% CI 1.464–8.649) the IgM positivity of those without a maculopapular rash (p = 0.005). There was also a significant association between the presence or absence of a maculopapular rash and rubella-specific IgG positivity in the multivariate logistic regression analysis. The pregnant women without a maculopapular rash had 2.5 times (95% CI 1.120–5.691) the protective antibody of those who had a maculopapular rash at the time of data collection (p = 0.026) (Table 3).

      Rubella IgM and IgG positivity in relation to the possible factors

      The majority of the IgM-positive pregnant women, nine (17.0%), had more than three children living in the given house (p = 0.240). Similarly, 249 (81.9%) of the IgG-positive pregnant women had one to three children living in the house (p = 0.727) and 18 (81.8%) had a history of blood transfusion (p = 0.639). None of these possible risk factors showed a statistically significant association in relation to either IgM or IgG positivity (Table 4). However, there were statistically significant differences in IgM positivity in relation to frequent exposure to children and study site on both univariate and multivariate analysis. The pregnant women who had frequent exposure to children in their daily activities had 2.8 times (95% CI 1.6–5.1) the IgM positivity of those who had no daily exposure to children (p = 0.001). In addition, the pregnant women from Dessie Referral Hospital had 2.8 times (95% CI 1.546–5.160) the IgM positivity of those pregnant women from University of Gondar Referral Hospital (Table 4) (p = 0.001).
      Table 4Rubella IgM and IgG antibodies in relation to possible factors for rubella virus infection among pregnant women in Amhara Regional State referral hospitals, Ethiopia, December 2015 to February 2017
      Possible risk factorsNumber testedIgM-positiveOnly IgG-positive
      Positive, n (%)COR (95% CI)AOR (95% CI)p-ValuePositive, n (%)COR (95% CI)p-Value
      Frequent exposure to children
       Yes27238 (14.0)2.6 (1.45–4.70)
      Significant association (p<0.05).
      2.8 (1.6–5.1)0.001216 (79.4)1
       No32819 (5.8)1261 (79.6)1.0 (0.68–1.50)0.961
      Number of children in a house
       None24327 (11.1)1189 (77.8)1
       1–330421 (6.9)0.6 (0.33–1.08)249 (81.9)1.1 (0.66–1.82)0.727
       >3539 (17.0)1.6 (0.72–3.72)39 (73.6)1.5 (0.54–3.93)0.456
      History of blood transfusion
       Yes222 (9.1)118 (81.8)1.4 (0.33–6.22)0.639
       No57855 (9.5)1.1 (0.24–4.62)459 (79.4)1
      Study site
       University of Gondar Referral Hospital35826 (7.3)11288 (80.4)1
       Felege-Hiwot Referral Hospital1158 (7.0)0.9 (0.42–2.17)0.9 (0.4–2.0)96 (83.5)1.2 (0.60–2.23)0.663
       Dessie Referral Hospital12723 (18.1)2.8 (1.55–5.16)
      Significant association (p<0.05).
      2.9 (1.6–5.4)0.00193 (73.2)1.1 (0.59–2.05)0.762
      COR, crude odds ratio; AOR, adjusted odds ratio; CI, confidence interval.
      a Significant association (p< 0.05).

      Discussion

      Rubella IgM and IgG antibodies are important immunoglobulins to study when investigating the prevalence of rubella in a given area (
      • Olajide Okikiola
      • Aminu Maryam
      • Randawa Abdullahi J.
      • Adejo Daniel S.
      Seroprevalence of rubella-specific IgM and IgG antibodies among pregnant women seen in a tertiary hospital in Nigeria.
      ). The presence of only IgM or both IgM and IgG antibodies at the same time indicates an acute/recent rubella virus infection. However, the presence of IgG antibody in the absence of IgM is a seromarker of immunity against rubella virus (
      • Taneja D.K.
      • Sharma P.
      Targeting rubella for elimination.
      ,
      • Peter Lombardo
      Dermatological manifestations of rubella work up: laboratory Studies. MedScape.
      ). The absence of both IgM and IgG antibodies indicates susceptibility to acquiring rubella infection. In this study, both rubella-specific IgM and IgG antibodies were analyzed among pregnant women to determine acute/recent infections and the levels of immunity against rubella virus infection in the pre-vaccine era in Ethiopia.
      The overall seroprevalence of rubella among pregnant women was found to be 89% (95% CI 86.3–91.3%). A similar finding has been reported from other African countries such as Senegal (90.1%) (
      • Dromigny J.A.
      • Nabeth P.
      • Perrier Gros Claude J.D.
      Evaluation of theseroprevalence of rubella in the region of Dakar, Senegal.
      ) and Namibia (85.0%) (
      • Jonas A.
      • Cardemil C.V.
      • Beukes A.
      • Anderson R.
      • Rota P.A.
      • Bankamp B.
      • et al.
      Rubella immunity among pregnant women aged 15-44 years, Namibia, 2010.
      ). However, the overall seroprevalence in this study is higher than reports from other African countries like the Democratic Republic of Congo (58.97%) (
      • Zanga Josue
      • Mbanzulu Makola Kennedy
      • Kabasele Arnold-Freddy
      • Ngatu Nlandu Roger
      • Wumba Dimosi Roger
      Rubella Seroprevalence and real-time PCR detection of RUBV among Congolese pregnant women.
      ), Sudan (65%) (
      • Hamdan Z.H.
      • Ismail E.
      • Abdelbagi I.E.
      • Nasser M.N.
      • Adam I.
      Seroprevalence of cytomegalovirus and rubella among pregnant women in western Sudan.
      ), and Nigeria (68%) (
      • Bamgboye A.E.
      • Afolabi K.A.
      • Esumeh F.I.
      • Enweani I.B.
      Prevalence of rubella antibody in pregnant women in Ibadan, Nigeria.
      ), and lower than reports from Burkina Faso (95%) (
      • Tahita Marc C.
      • Hübschen Judith M.
      • Tarnagda Zekiba
      • Ernest Da
      • Charpentier
      • Kremer Jacques R.
      • et al.
      Rubella seroprevalence among pregnant women in Burkina Faso.
      ,
      • Tahita M.C.
      • Hubschen J.
      • Tarnagda Z.
      • Ernest D.
      • Charpentier E.
      • Kremer J.R.
      Rubella seroprevalence among pregnant women in Burkina Faso.
      ) and Zimbabwe (92%) (
      • Mamvura Tafadzwa Shepherd
      • Chin’ombe Nyasha
      • Ruhanya Vurayai
      • Nziramasanga Pasipanodya
      Seroprevalence of Rubella Virus IgG in pregnant women in Harare, Zimbabwe.
      ). This variation in different studies might be due to the difference in the endemicity of the virus, the variation in the sample size of the studies, the laboratory methods used, and differences in the cut-off points of the assays used.
      Although there is some variation among countries in terms of the concentration of IgG antibodies considered to be protective (
      • WHO
      Rubella vaccines WHO position paper.
      ), based on the previous recommendations of the US National Committee for Clinical Laboratory Standards (NCCLS) (
      • Skendzel L.P.
      Rubella immunity: defining the level of protective antibody.
      ), international agreements and guidelines (
      • Cutts F.T.
      • Vynnycky E.
      Modelling the incidence of congenital rubella syndrome in developing countries.
      ,
      • Dimech W.
      • Panagiotopoulos L.
      • Francis B.
      • Laven N.
      • Marler J.
      • Dickeson D.
      • et al.
      Evaluation of eight anti-rubella virus immunoglobulin g immunoassays that report results in international units per millilitre.
      ), in the absence of IgM, pregnant women who had rubella IgG levels ≥10 IU/ml were classified as immune and those with IgG levels <10 IU/ml were classified as susceptible. In the present study, 79.5% (95% CI 76.3–82.5%) of the pregnant women had IgG levels of >10 IU/ml. None of these pregnant women had a previous history of rubella vaccination and they were immune from wild-type rubella infections. This might be due to the endemicity of the virus in the study area and sustained previous infections of the study participants before conception or during their childhood, as rubella infection is common among children and teenagers in the country (
      • Shiferaw Dejenie
      • Birke Teklu
      • Esete Teshome
      • Ayenachew Assefa
      • Ketema BekeleHiwot
      • Beyene Berhane
      The epidemiology of laboratory confirmed rubella cases in Oromia Region, Ethiopia, 2010–2015: data from the measles case-based surveillance system.
      ).
      The prevalence of rubella IgG in this study was also comparable to that reported in Burkina Faso (77%) (
      • Tahita Marc C.
      • Hübschen Judith M.
      • Tarnagda Zekiba
      • Ernest Da
      • Charpentier
      • Kremer Jacques R.
      • et al.
      Rubella seroprevalence among pregnant women in Burkina Faso.
      ), but it was higher than the prevalence reported in Niger (53%) (
      • Onakewhor J.U.
      • Chiwuzie J.
      Seroprevalence survey of rubella infection in pregnancy at the University of Benin Teaching Hospital, Benin City, Nigeria.
      ) and southern India (65%) (
      • Padmaja M.
      • Radhakrishna P.M.
      • Varghese S.J.
      Seroprevalence of immunity to rubella in pregnant women.
      ). However, the IgG positivity rate in this study was lower than that found in studies conducted in other countries like Nigeria (97.9%) (
      • Mohammed D.A.
      • Shittu O.
      • Sadauki H.
      • Olayinka A.
      • Kolawole B.
      • Adejo D.
      Prevalence of rubella IgG antibodies among pregnant women in Zaria, Nigeria.
      ), Cameroon (88.6%) (
      • Fokunang C.N.
      • Chia J.
      • Ndumbe P.
      • Mbu P.
      • Atashili J.
      Clinical studies on seroprevalence of rubella virus in pregnant women of Cameroon regions.
      ), Turkey (96.1%) (
      • Tamer G.S.
      • Dundar D.
      • Caliskan E.
      Seroprevalence of Toxoplasma gondii, rubella and cytomegalovirus among pregnant women in western region of Turkey.
      ), Italy (85.8%) (
      • Calimeri C.A.
      • Fauci V.L.A.
      • Squeri R.
      • Grillo O.C.
      • Lo Giudice D.
      Prevalence of serum anti-rubella virus antibodies among pregnant women in southern Italy.
      ), and Mexico (97.1%) (
      • Alvarado-Esquivel Cosme
      • Hernandez-Tinoco Jesus
      • Sanchez-Anguiano Luis Francisco
      • Ramos-Nevarez Agar
      • Cerrillo-Soto Sandra Margarita
      • Salas-Pacheco Jose Manuel
      Rubella immune status in pregnant women in a Northern Mexican City.
      ). These variations in rubella IgG positivity in different countries might be due to the difference in the endemicity of the rubella virus and the presence or absence of rubella vaccination in their immunization programs.
      According to the WHO, the incidence of rubella in Ethiopia was 7.27 per million inhabitants in 2017 and 5.39 per million inhabitants in 2018 (
      • WHO
      Measles and rubella surveillance data. WHO-immunization, vaccines and biologicals.
      ). However, due to the benign nature of the virus and lack of independent rubella surveillance system in the country, most of the rubella reports might be from measles-suspected cases, as discussed earlier. The existing burden of the virus among women of child-bearing age might therefore be underestimated. In the present study, 9.5% of the pregnant women were positive for rubella IgM. As rubella IgM mostly declines quickly and is usually undetectable at 2–3 months after the infection (
      • Vardas Eftyxia
      Rubella lancet laboratories.
      ), the present result indicates the presence of acute rubella virus infection at 0–3 months before the blood samples were obtained. Of the total pregnant women, 8.2% had both rubella IgM and IgG antibodies. As rubella virus re-infection following natural immunity is very rare (
      • Mendelson Ella
      • Aboudy Yair
      • Smetanac Zahava
      • Tepperberg Michal
      • Grossman Zahava
      Laboratory assessment and diagnosis of congenital viral infections: rubella, cytomegalovirus (CMV), varicella-zoster virus (VZV), herpes simplex virus (HSV), parvovirus B19 and human immunodeficiency virus (HIV).
      ), the pregnant women who had both IgM and IgG antibodies might have been in the resolving stages of primary rubella infections. Since the majority of these pregnant women were in the third trimester of pregnancy, they might have acquired the infection during the first or second trimester of pregnancy and subsequently developed IgG antibodies within 30 days of infection (
      • Navigator ClinLab
      Rubella.
      ). This indicates that these groups of pregnant women might not be immune before becoming pregnant and their fetuses may not be excluded from rubella-associated risks. Although there is a scarcity of data about CRS in the country, as indicated earlier (
      • Mekonnen Demeke
      Clinically confirmed congenital rubella syndrome: the role of echocardiography.
      ), the newborns from women infected with rubella during early pregnancy might acquire a congenital rubella infection and be born with rubella-associated congenital anomalies or CRS. Therefore, the screening of women of child-bearing age before conception or during pregnancy might be crucial to reduce the consequences of acute rubella infection during pregnancy.
      A similar IgM seroprevalence was also reported in Nigeria (9.2%) (
      • Onakewhor J.U.
      • Chiwuzie J.
      Seroprevalence survey of rubella infection in pregnancy at the University of Benin Teaching Hospital, Benin City, Nigeria.
      ). However, the IgM positivity rate in the present study was higher than those reported recently from Southern Ethiopia (
      • Tamirat Biniam
      • Hussen Techalew
      • Shimelis Siraj
      Rubella virus infection and associated factors among pregnant women attending the antenatal care clinics of public hospitals in Hawassa City, Southern Ethiopia: a crosssectional study.
      ) and Turkey (2%) (
      • Tamer G.S.
      • Dundar D.
      • Caliskan E.
      Seroprevalence of toxoplasma gondii, rubella and cytomegalovirus among pregnant women in western region of Turkey.
      ). In contrast, the present study result was lower than that in another report from Nigeria (38.8%) (
      • Olajide Okikiola
      • Aminu Maryam
      • Randawa Abdullahi J.
      • Adejo Daniel S.
      Seroprevalence of rubella-specific IgM and IgG antibodies among pregnant women seen in a tertiary hospital in Nigeria.
      ). These variations in rubella-specific IgM positivity might be due to the difference in endemicity of the rubella virus and sustained transmission in susceptible groups, differences in population density, variations in temperature/humidity, and the presence or absence of rubella vaccination, as discussed earlier.
      No statistically significant difference in rubella IgM and IgG positivity was found in relation to most socio-demographic characteristics of the pregnant women in this study. A similar finding was also reported in a recent study in Southern Ethiopia (
      • Tamirat Biniam
      • Hussen Techalew
      • Shimelis Siraj
      Rubella virus infection and associated factors among pregnant women attending the antenatal care clinics of public hospitals in Hawassa City, Southern Ethiopia: a crosssectional study.
      ), and in other studies in Nigeria (
      • Pennap G.R.
      • Egwa M.A.
      Prevalence of rubella virus infection among pregnant women accessing antenatal clinic at federal medical centre, Keffi, Nigeria.
      ) and Namibia (
      • Jonas A.
      • Cardemil C.V.
      • Beukes A.
      • Anderson R.
      • Rota P.A.
      • Bankamp B.
      • et al.
      Rubella immunity among pregnant women aged 15-44 years, Namibia, 2010.
      ). However, a statistically significant association between IgM positivity and area of residence was found in the present study; pregnant women from urban settings had two times the IgM positivity of those from rural settings. Although further study of rubella virus transmission dynamics in rural and urban settings is needed, this difference in IgM positivity between the two settings might be due to differences in population density. The high population density in urban areas might increase the contact rate and, as discussed earlier, pregnant women without protective levels of rubella immunity might acquire the infections. A similar finding was also reported in the pre-vaccine era in other countries (
      • Goodson J.L.
      • Masresha B.
      • Dosseh A.
      • Byabamazima C.
      • Nshimirimana D.
      • Cochi S.
      • et al.
      Rubella epidemiology in Africa in the prevaccine era, 2002–2009.
      ,
      • Assaad F.
      • Ljungars-Esteves K.
      Rubella-world impact.
      ,
      • Hinman A.R.
      • Hersh B.S.
      • de Quadros C.A.
      Rational use of rubella vaccine for prevention of congenital rubella syndrome in the Americas.
      ).
      In this study, there was no statistically significant difference in rubella antibody positivity according to the trimester of pregnancy of the women, as has been reported in other studies (
      • Agbede O.O.
      Sero-prevalence of antenatal rubella in UITH.
      ,
      • Olajide Okikiola
      • Aminu Maryam
      • Randawa Abdullahi J.
      • Adejo Daniel S.
      Seroprevalence of rubella-specific IgM and IgG antibodies among pregnant women seen in a tertiary hospital in Nigeria.
      ). However, emphasis should be placed on those pregnant women who have had recent or acute infections due to the teratogenic nature of the virus (
      • Lee J.Y.
      • Bowden D.S.
      Rubella virus replication and links to teratogenicity.
      ). In the present study, there was a statistically significant association between a previous history of spontaneous abortion and IgM positivity. Pregnant women with a history of one to three previous spontaneous abortions had 2.5 times the IgM positivity rate of those without a history of spontaneous abortion. An explanation for this is that those pregnant women who have a previous bad obstetric history (BOH) may be more vulnerable to acquiring acute rubella infections (
      • Priyanka D.
      • Vallab Ganesh Anupriya A.
      • Uma A.
      • Kalamani S.M.
      Seroprevalence of rubella among asymptomatic pregnant women in a rural teaching hospital.
      ). Although the mechanism is not clear and further studies are needed, a similar finding has also been reported in other studies (
      • Noor Al- Huda Ali A. H. Saeed
      • Liqaa Jameel Ibraheem
      • Areej Abbas Zabbon
      • Enas Waleed Shakir
      Seroprevalence study of rubella virus infection among bad obstetric history and primigravida pregnant women in Iraq.
      ,
      • Abdolreza Sotoodeh Jahromi
      • Akbar Kazemi
      • Gita Manshoori
      • Abdolhossien Madani
      • Seyed-Hamid Moosavy
      • Bita Seddigh
      Seroprevalence of rubella virus in women with spontaneous abortion.
      ).
      With regard to the relationship between IgG positivity and previous reproductive history, there was a statistically significant difference in the levels of IgG according to the absence of a previous history of spontaneous abortion. Pregnant women without a previous history of spontaneous abortion had 1.7 times the IgG positivity of those who had a previous history of spontaneous abortion. An explanation for this is that these groups of pregnant women might have acquired the rubella infection during their childhood and developed protective immunity against rubella virus at their reproductive age.
      Even though the clinical manifestations of rubella are non-specific and it is difficult to diagnose clinically (
      • WHO
      Field guidelines for surveillance of measles, rubella and congenital rubella syndrome.
      ), the present study found statistically significant differences in rubella IgM or IgG positivity according to the presence or absence of certain clinical manifestations in the pregnant women at the time of data collection. Although it was not statistically significant in the multivariate analysis, pregnant women with lymphadenopathy had three times the IgM positivity rate of those without lymphadenopathy. The pregnant women with a maculopapular rash had 3.5 times the IgM positivity of those without a maculopapular rash.
      In contrast, pregnant women without a maculopapular rash had 2.5 times the protective IgG antibody compared to those who had a maculopapular rash. There was, however, no statistically significant difference in the presence or absence of other clinical manifestations and IgM/IgG positivity. The lack of association between IgM/IgG positivity and most clinical manifestations may be due to the mild nature of rubella infections (
      • Edlich R.F.
      • Winters K.L.
      • Long W.B.
      • Gubler K.D.
      Rubella and congenital rubella (German measles).
      ). Furthermore, most patients with rubella may recover without any complications or sequelae and pass unnoticed, as rubella virus mostly causes a self-limiting disease in postnatal infections (
      • Mwambe Berno
      • Mirambo Mariam M.
      • Mshana Stephen E.
      • Massinde Anthony N.
      • Kidenya Benson R.
      • Michael Denna
      • et al.
      Sero-positivity rate of rubella and associated factors among pregnant women attending antenatal care in Mwanza, Tanzania.
      ,
      • Edlich R.F.
      • Winters K.L.
      • Long W.B.
      • Gubler K.D.
      Rubella and congenital rubella (German measles).
      ,
      • Forrest Jill M.
      • Mense Margaret A.
      Recent implications of intrauterine and postnatal rubella.
      ).
      When a comparison was made of the possible risk factors and rubella IgM positivity, the pregnant women who had frequent exposure to children in their daily activities had 2.8 times the IgM positivity of those who had no daily exposure. This can be explained by the fact that rubella infection is more common in childhood (
      • Junaid S.A.
      • Akpan K.J.
      • Olabode A.O.
      Sero-survey of rubella IgM antibodies among children in Jos, Nigeria.
      ) and children might harbor and spread the infection to susceptible pregnant women. Similarly, the pregnant women from Dessie Referral Hospital had 2.8 times the IgM positivity rate of pregnant women from University of Gondar Referral Hospital. This indicates that there may be epidemiological differences in the circulation of rubella virus within the country. In addition, there may also have been differences in temperature and humidity between the study sites at the time of data collection. These differences might have contributed to the differences in active transmission of rubella virus in the study areas.
      Although maternal immunity is protective against intrauterine rubella infection (
      • Aboudy Y.
      • Fogel A.
      • Barnea B.
      • Mendelson E.
      • Yosef L.
      • Frank T.
      Subclinical rubella reinfection during pregnancy followed by transmission of virus to the fetus.
      ), around 11% (95% CI 8.7–13.7%) of the study participants had IgG levels ≤10 IU/ml; these women were classified as seronegative and represent the susceptible group. A similar finding has also been reported in previous studies (
      • Yadav S.
      • Gupta S.
      • Kumari S.
      Sero-prevalence of rubella in women of reproductive age group.
      ,
      • Pooja D.
      • Piyush G.
      Burden of congenital rubella syndrome (CRS) in India: a systematic review.
      ,
      • Oyinloye S.O.
      • Amama C.A.
      • Daniel R.
      • Ajayi B.B.
      • Lawan M.A.
      Seroprevalence survey of rubella antibodies among pregnant women in Maiduguri, Borno State, Nigeria.
      ). In developing countries, about 10–25% of women have been reported to be seronegative (
      • Cutts F.T.
      • Robertson S.E.
      • Diaz-Ortega J.L.
      • Samuel R.
      Control of rubella and congenital rubella syndrome (CRS) in developing countries, part 1: burden of disease from CRS.
      ,
      • Gavin B.G.
      • Susan E.R.
      • Alya D.
      • Gacic-Dobo M.
      • Peter M.S.
      Rubella and congenital rubella syndrome control and elimination—global progress, 2000-2014.
      ), and countries with high rates of susceptibility to rubella virus among women of child-bearing age might be at risk of CRS (
      • Lambert Nathaniel
      • Strebel Peter
      • Orenstein Walter
      • Icenogle Joseph
      • Poland Gregory A.
      Rubella.
      ). The susceptibility rate of 10% among adult women could result in outbreaks of CRS (
      • WHO
      Rubella vaccines WHO position paper.
      ). Therefore, attention must be paid to the susceptible group of women in this study in order to reduce the risk of CRS in their future pregnancies.

      Limitations of the study

      Due to the lack facilities, it was not possible to use advanced laboratory techniques like RT-PCR for the diagnosis of rubella. Furthermore, due to the nature of the study (cross-sectional study) and reagent constraints, it was not possible to obtain convalescent sera from each rubella IgM-positive/IgG-negative study participant. Since the study was conducted only in the selected referral hospitals of Amhara Regional State, Ethiopia, a large-scale community-based study might be important. However, as there is scarcity of data about rubella among pregnant women in the country, the information provided by this study might serve as a baseline for the study area and increase awareness for health decision-makers and collaborators in the country so that the long-term health consequences can be reconsidered.

      Conclusions

      The seroprevalence of rubella virus was found to be high, and many (9.5%) of the pregnant women had acute rubella virus infections at the time of data collection. This implies that the virus is endemic in the study areas. Despite 79.5% of pregnant women having IgG levels >10 IU/ml and being immune to natural/wild-type rubella virus infections, about 11% of the pregnant women were found to be non-immune and represent the susceptible group. These pregnant women may be at risk of developing rubella-associated congenital anomalies in their future pregnancies. Hence, the screening of women of child-bearing age before conception, introduction of rubella vaccination, and a strong surveillance system might be important to reduce rubella-associated health complications in the country.

      Acknowledgements

      We would like to thank the University of Gondar for funding the project. Our special thanks also go to all of the study participants, data collectors, and other staff at the respective referral hospitals for their cooperation during the data collection process.

      Ethical approval

      The study was conducted after obtaining institutional ethical clearance from the Ethics Committee of the University of Gondar. A letter of agreement and the cooperation of the clinical director/chief executive officer of each referral hospital were obtained. Informed consent was also obtained from each study participant, as per the National Research Ethics Review Guidelines (
      • FDRE-MST
      National research ethics review guideline.
      ). We also obtained written consent from each study participant to publish the findings in a peer-reviewed journal for the scientific community.

      Funding

      For data collection and laboratory reagents/materials, funding was obtained from the University of Gondar.

      Conflict of interest

      The authors declare that no competing interest exists with respect to the authorship and/or publication of this research paper.

      Author contributions

      YW: Participated in the conception, design and proposed the research idea, data collection, data clearance, entry, analysis and interpretation of the findings and drafting the manuscript and write-up. MT: Participated in the conception, design and proposed the research idea, supervision/consultations during data collection and interpretations of the findings. BA: Participated in consultation during data collection and interpretations of the findings. GF, MW, and MB: Participated in data collection and interpretations of the findings. BT: Participated in the conception, design and proposed the research idea, supervision/consultations during data collection and interpretations of the findings. All authors reviewed and approved the final manuscript.

      References

        • Abdolreza Sotoodeh Jahromi
        • Akbar Kazemi
        • Gita Manshoori
        • Abdolhossien Madani
        • Seyed-Hamid Moosavy
        • Bita Seddigh
        Seroprevalence of rubella virus in women with spontaneous abortion.
        Am J Infect Dis. 2011; 7: 16-19
        • Aboudy Y.
        • Fogel A.
        • Barnea B.
        • Mendelson E.
        • Yosef L.
        • Frank T.
        Subclinical rubella reinfection during pregnancy followed by transmission of virus to the fetus.
        J Infect. 1997; 34: 273-276
        • Adam O.
        • Makkawi T.
        • Kannan A.
        • Osman M.E.
        Seroprevalence of rubella among pregnant women in Khartoum state, Sudan.
        East Mediterr Health J. 2013; 9: 812-815
        • Adewumi Olubusuyi M.
        • Olayinka Adebowale O.
        • Olusola Babatunde A.
        • Faleye Temitope O.C.
        • Sule Waidi F.
        • Adesina Olubukola
        Epidemiological evaluation of rubella virus infection among pregnant women in Ibadan, Nigeria.
        Peer J. 2014; 1: 613
        • Agbede O.O.
        Sero-prevalence of antenatal rubella in UITH.
        Open Public Health J. 2011; 5: 10-11
        • Al-Rubai B.
        • Aboud M.
        • Hamza W.
        Evaluation of anti- rubella antibodies among childbearing age women in Babylon Governorate.
        Med J Babylon. 2010; 7: 2
        • Alleman Mary M.
        • Wannemuehler Kathleen A.
        • Hao Lijuan
        • Perelyginab Ludmila
        • Icenogle Joseph P.
        • Vynnycky Emilia
        • et al.
        Estimating the burden of rubella virus infection and congenital rubella syndrome through a rubella immunity assessment among pregnant women in the Democratic Republic of the Congo: potential impact on vaccination policy.
        Vaccine. 2016; 34: 6502-6511
        • Alvarado-Esquivel Cosme
        • Hernandez-Tinoco Jesus
        • Sanchez-Anguiano Luis Francisco
        • Ramos-Nevarez Agar
        • Cerrillo-Soto Sandra Margarita
        • Salas-Pacheco Jose Manuel
        Rubella immune status in pregnant women in a Northern Mexican City.
        J Clin Med Res. 2016; 8
        • Assaad F.
        • Ljungars-Esteves K.
        Rubella-world impact.
        Rev Infect Dis. 1985; 7: 29-36
        • Bamgboye A.E.
        • Afolabi K.A.
        • Esumeh F.I.
        • Enweani I.B.
        Prevalence of rubella antibody in pregnant women in Ibadan, Nigeria.
        West Afr Med J. 2004; 23: 245-248
        • CDC
        Control and prevention of rubella: evaluation and management of suspected outbreaks, rubella in pregnant women, and surveillance for congenital rubella syndrome.
        MMWR Recomm Rep. 2001; 50: 1-23
        • CDC
        Progress toward control of rubella and prevention of congenital rubella syndrome worldwide, 2009.
        Morbid Mortal Weekly Rep. 2010; 59: 1307-1310
        • Calimeri C.A.
        • Fauci V.L.A.
        • Squeri R.
        • Grillo O.C.
        • Lo Giudice D.
        Prevalence of serum anti-rubella virus antibodies among pregnant women in southern Italy.
        Int J Gynecol Obstet. 2012; 116: 211-213
        • Cradock-Watson J.E.
        • Ridehalg M.K.S.
        • Anderson M.J.
        • Pattison J.R.
        Outcome of asymptomatic infection with rubella virus during pregnancy.
        J Hyg. 1981; 87: 147-154
        • Cutts F.T.
        • Vynnycky E.
        Modelling the incidence of congenital rubella syndrome in developing countries.
        Indian J Epidemiol. 1999; 28: 1176-1184
        • Cutts F.T.
        • Abebe A.
        • Messele T.
        • Dejene A.
        • Enquselassie F.
        • Nigatu W.
        • et al.
        Sero-epidemiology of rubella in the urban population of Addis Ababa, Ethiopia.
        Epidemiol Infect. 2000; 124: 467-479
        • Cutts F.T.
        • Robertson S.E.
        • Diaz-Ortega J.L.
        • Samuel R.
        Control of rubella and congenital rubella syndrome (CRS) in developing countries, part 1: burden of disease from CRS.
        Department of Vaccines and Biologicals Geneva: World Health Organization, 2000: 5
        • Demicheli V.
        • Debalini M.G.
        • Di Pietrantonj C.
        Vaccines for measles, mumps and rubella in children.
        Cochrane Database Syst Rev. 2012; : 2
        • Dimech W.
        • Panagiotopoulos L.
        • Francis B.
        • Laven N.
        • Marler J.
        • Dickeson D.
        • et al.
        Evaluation of eight anti-rubella virus immunoglobulin g immunoassays that report results in international units per millilitre.
        J Clin Microbiol. 2008; 46: 1955-1960
        • Dromigny J.A.
        • Nabeth P.
        • Perrier Gros Claude J.D.
        Evaluation of theseroprevalence of rubella in the region of Dakar, Senegal.
        Trop Med Int Health. 2003; 8: 740-743
        • Edlich R.F.
        • Winters K.L.
        • Long W.B.
        • Gubler K.D.
        Rubella and congenital rubella (German measles).
        J Long Term Eff Med Implants. 2005; 15: 319-328
        • FDRE-MST
        National research ethics review guideline.
        Fifth Edition. Ministry of Science and Technology (MST), 2014: 1-95
        • Fokunang C.N.
        • Chia J.
        • Ndumbe P.
        • Mbu P.
        • Atashili J.
        Clinical studies on seroprevalence of rubella virus in pregnant women of Cameroon regions.
        Afr J Clin Exp Microbiol. 2010; 11: 79-94
        • Forrest Jill M.
        • Mense Margaret A.
        Recent implications of intrauterine and postnatal rubella.
        J Paediatr Child Health. 2008; 11: 65-75
        • Gavin B.G.
        • Susan E.R.
        • Alya D.
        • Gacic-Dobo M.
        • Peter M.S.
        Rubella and congenital rubella syndrome control and elimination—global progress, 2000-2014.
        World Health Organ Weekly Epidemiol Record. 2015; : 510-516
        • Gebreselassie Lakew
        • Almaz Abebe
        The immune status of young adult females in Ethiopia to rubella virus infection.
        Bull World Health Organ. 1985; 63: 927-930
        • Getahun Mekonen
        • Beyene Berhane
        • Gallagher Kathleen
        • Ademe Ayesheshem
        • Teshome Birke
        • Tefera Mesfin
        • et al.
        Epidemiology of rubella virus cases in the pre-vaccination era of Ethiopia, 2009–2015.
        BMC Public Health. 2016; 16: 1-7
        • Gilbert Nicolas L.
        • Rotondo Jenny
        • Shapiro Janna
        • Sherrard Lindsey
        • Fraser William D.
        • Ward Brian J.
        Seroprevalence of rubella antibodies and determinants of susceptibility to rubella in a cohort of pregnant women in Canada, 2008–2011.
        Vaccine. 2017; 35: 3050-3055
        • Goodson J.L.
        • Masresha B.
        • Dosseh A.
        • Byabamazima C.
        • Nshimirimana D.
        • Cochi S.
        • et al.
        Rubella epidemiology in Africa in the prevaccine era, 2002–2009.
        J Infect Dis. 2011; 203: S215-S225
        • Hamdan Z.H.
        • Ismail E.
        • Abdelbagi I.E.
        • Nasser M.N.
        • Adam I.
        Seroprevalence of cytomegalovirus and rubella among pregnant women in western Sudan.
        Virol J. 2011; 8
        • Heggie A.D.
        • Robbins F.C.
        Natural rubella acquired after birth: clinical features and complications.
        Am J Dis Children. 1969; 118: 12-17
        • Hinman A.R.
        • Hersh B.S.
        • de Quadros C.A.
        Rational use of rubella vaccine for prevention of congenital rubella syndrome in the Americas.
        Rev Panam Salud Publica. 1998; 4: 156-160
        • Horstmann D.M.
        • Riordan J.T.
        • Ohtawara M.
        • Niederman J.C.
        A natural epidemic of rubella in a closed population: virological and epidemiological observations.
        Arch Gesamte Virusforsch. 1965; 16: 483-487
        • Jonas A.
        • Cardemil C.V.
        • Beukes A.
        • Anderson R.
        • Rota P.A.
        • Bankamp B.
        • et al.
        Rubella immunity among pregnant women aged 15-44 years, Namibia, 2010.
        Int J Infect Dis. 2016; 49: 196-201
        • Junaid S.A.
        • Akpan K.J.
        • Olabode A.O.
        Sero-survey of rubella IgM antibodies among children in Jos, Nigeria.
        Virol J. 2011; 8: 1-5
        • Kolawole O.M.
        • Anjori E.O.
        • Adekanle D.A.
        • Kolawole C.F.
        • Durowade K.A.
        Seroprevalence of rubella IgG antibody in pregnant women in Osogbo, Nigeria.
        Int J Prev Med. 2014; 5
        • Lambert Nathaniel
        • Strebel Peter
        • Orenstein Walter
        • Icenogle Joseph
        • Poland Gregory A.
        Rubella.
        Lancet. 2015; 385: 2297-2307
        • Lee J.Y.
        • Bowden D.S.
        Rubella virus replication and links to teratogenicity.
        Clin Microbiol Rev. 2000; 13: 571-587
        • Lezan M.M.
        Prevalence of rubella virus in pregnant women in Kirkuk City-Iraq.
        Kirkut Univ J Sci Stud. 2015; 10: 47-57
        • Mamvura Tafadzwa Shepherd
        • Chin’ombe Nyasha
        • Ruhanya Vurayai
        • Nziramasanga Pasipanodya
        Seroprevalence of Rubella Virus IgG in pregnant women in Harare, Zimbabwe.
        Germs. 2015; 5: 50-52
        • Martínez-Quintana E.
        • Castillo-Solórzano C.
        • Torner N.
        • Rodríguez-González F.
        Congenital rubella syndrome: a matter of concern.
        Pan Am J Public Health. 2015; 37: 179-186
        • Mekonnen Demeke
        Clinically confirmed congenital rubella syndrome: the role of echocardiography.
        Ethiop J Health Sci. 2017; 27: 197-202
        • Mendelson Ella
        • Aboudy Yair
        • Smetanac Zahava
        • Tepperberg Michal
        • Grossman Zahava
        Laboratory assessment and diagnosis of congenital viral infections: rubella, cytomegalovirus (CMV), varicella-zoster virus (VZV), herpes simplex virus (HSV), parvovirus B19 and human immunodeficiency virus (HIV).
        Reprod Toxicol. 2006; 21: 350-382
        • Mirambo Mariam M.
        • Majigo Mtebe
        • Aboud Said
        • Groß Uwe
        • Mshana Stephen E.
        Serological makers of rubella infection in Africa in the pre vaccination era: a systematic review.
        BMC Res Note. 2015; 8: 1-7
        • Mitiku Kassahun
        • Bedada Tesfaye
        • Masresha Balcha
        • Kegne Wendemagegn
        • Nafo-Traore Fatoumata
        • Tesfaye Neghist
        • et al.
        The epidemiology of rubella disease in ethiopia: data from the measles case-based surveillance system.
        J Infect Dis. 2011; 204: 239-242
        • Mohammed D.A.
        • Shittu O.
        • Sadauki H.
        • Olayinka A.
        • Kolawole B.
        • Adejo D.
        Prevalence of rubella IgG antibodies among pregnant women in Zaria, Nigeria.
        Int Health. 2010; 2: 156-159
        • Mounerou S.
        • Maléwé K.
        • Anoumou D.Y.
        • Sami N.
        • Koffi A.
        • Mireille P.
        Seroprevalence of rubella IgG antibody among pregnant women attending antenatal clinic in Lomé, Togo.
        Am J Infect Dis Microbiol. 2015; 3: 134-136
        • Mwambe Berno
        • Mirambo Mariam M.
        • Mshana Stephen E.
        • Massinde Anthony N.
        • Kidenya Benson R.
        • Michael Denna
        • et al.
        Sero-positivity rate of rubella and associated factors among pregnant women attending antenatal care in Mwanza, Tanzania.
        BMC Pregnancy Childbirth. 2014; 14: 1-5
        • Navigator ClinLab
        Rubella.
        2013 (Available from: http://www.clinlabnavigator.com/rubella.html. [cited October 18/207])
        • Njeru Ian
        • Onyango Dickens
        • Ajack Yusuf
        • Kiptoo Elizabeth
        Rubella outbreak in a Rural Kenyan District, 2014: documenting the need for routine rubella immunization in Kenya.
        BMC Infect Dis. 2015; 15: 1-6
        • Noor Al- Huda Ali A. H. Saeed
        • Liqaa Jameel Ibraheem
        • Areej Abbas Zabbon
        • Enas Waleed Shakir
        Seroprevalence study of rubella virus infection among bad obstetric history and primigravida pregnant women in Iraq.
        World J Pharmaceut Res. 2015; 4: 378-384
        • Olajide Okikiola
        • Aminu Maryam
        • Randawa Abdullahi J.
        • Adejo Daniel S.
        Seroprevalence of rubella-specific IgM and IgG antibodies among pregnant women seen in a tertiary hospital in Nigeria.
        Int J Women Health. 2015; 2015: 75-83
        • Onakewhor J.U.
        • Chiwuzie J.
        Seroprevalence survey of rubella infection in pregnancy at the University of Benin Teaching Hospital, Benin City, Nigeria.
        Niger J Clin Pract. 2011; 14: 140-145
        • Oyinloye S.O.
        • Amama C.A.
        • Daniel R.
        • Ajayi B.B.
        • Lawan M.A.
        Seroprevalence survey of rubella antibodies among pregnant women in Maiduguri, Borno State, Nigeria.
        Afr J Clin Exp Microbiol. 2013; 14: 1595-1689
        • Padmaja M.
        • Radhakrishna P.M.
        • Varghese S.J.
        Seroprevalence of immunity to rubella in pregnant women.
        Natl Med J India. 2010; 23: 248-249
        • Pennap G.R.
        • Egwa M.A.
        Prevalence of rubella virus infection among pregnant women accessing antenatal clinic at federal medical centre, Keffi, Nigeria.
        Int J Curr Microb. 2016; 5: 171-178
        • Peter Lombardo
        Dermatological manifestations of rubella work up: laboratory Studies. MedScape.
        2015 (Available from: http://emedicine.medscape.com/article/1133108-workup. [cited March 28, 2017])
        • Pooja D.
        • Piyush G.
        Burden of congenital rubella syndrome (CRS) in India: a systematic review.
        Indian Pediatr. 2012; 49: 377-399
        • Priyanka D.
        • Vallab Ganesh Anupriya A.
        • Uma A.
        • Kalamani S.M.
        Seroprevalence of rubella among asymptomatic pregnant women in a rural teaching hospital.
        Int J Med Microbiol Res. 2017; 1: 7-12
        • Robertson S.E.
        • Featherstone D.A.
        • Gacic-Dobo M.
        • Hersh B.S.
        Rubella and congenital rubella syndrome: global update.
        Rev Panam Salud Publica. 2003; 14: 306-315
        • Sandow D.
        • Okubagzhi G.S.
        • Arnold U.
        • Denkmann N.
        Seroepidemiological study on rubella in pregnant women in Gondar Region, Northern Ethiopia.
        Ethiop Med J. 1982; 20: 173-178
        • Sherman F.E.
        • Michaels R.H.
        • Kenny F.M.
        Acute encephalopathy (encephalitis) complicating rubella: report of cases with virologic studies, cortisol-production determinations, and observations at autopsy.
        J Am Med Assoc. 1965; 192: 675-681
        • Shiferaw Dejenie
        • Birke Teklu
        • Esete Teshome
        • Ayenachew Assefa
        • Ketema BekeleHiwot
        • Beyene Berhane
        The epidemiology of laboratory confirmed rubella cases in Oromia Region, Ethiopia, 2010–2015: data from the measles case-based surveillance system.
        Am J Clin Pathol. 2016; 146: 227
        • Skendzel L.P.
        Rubella immunity: defining the level of protective antibody.
        Am J Clin Pathol. 1996; 106: 170-174
        • Tahita Marc C.
        • Hübschen Judith M.
        • Tarnagda Zekiba
        • Ernest Da
        • Charpentier
        • Kremer Jacques R.
        • et al.
        Rubella seroprevalence among pregnant women in Burkina Faso.
        BMC Infect Dis. 2013; 13: 164
        • Tahita M.C.
        • Hubschen J.
        • Tarnagda Z.
        • Ernest D.
        • Charpentier E.
        • Kremer J.R.
        Rubella seroprevalence among pregnant women in Burkina Faso.
        BMC Infect Dis. 2013; 13
        • Tamer G.S.
        • Dundar D.
        • Caliskan E.
        Seroprevalence of Toxoplasma gondii, rubella and cytomegalovirus among pregnant women in western region of Turkey.
        Clin Invest Med. 2008; 32: E43-E47
        • Tamer G.S.
        • Dundar D.
        • Caliskan E.
        Seroprevalence of toxoplasma gondii, rubella and cytomegalovirus among pregnant women in western region of Turkey.
        Clin Invest Med. 2009; 32: 43-47
        • Tamirat Biniam
        • Hussen Techalew
        • Shimelis Siraj
        Rubella virus infection and associated factors among pregnant women attending the antenatal care clinics of public hospitals in Hawassa City, Southern Ethiopia: a crosssectional study.
        BMJ Open. 2017; 7: 1-8
        • Taneja D.K.
        • Sharma P.
        Targeting rubella for elimination.
        Indian J Public Health. 2012; 56: 269-272
        • Vardas Eftyxia
        Rubella lancet laboratories.
        2011 (Available from: http://www.lancet.co.za/index.php/pathology-centre/pathology-newsletters/virology/rubella/. [cited February 04/2015])
        • WHO
        Progress towards eliminating rubella and congenital rubella syndrome in the western hemisphere, 2003-2008.
        Wkly Epidemiol Rec. 2008; 83: 395-400
        • WHO
        Field guidelines for surveillance of measles, rubella and congenital rubella syndrome.
        World Health Organization Regional office for the Eastern Mediterranean Region, 2011: 1-52
        • WHO
        Rubella vaccines WHO position paper.
        Wkly Epidemiol Rec. 2011; 86: 301-316
        • WHO
        Global measles and rubella strategic plan: 2012-2020.
        World Health Organization, 2012: 1-44
        • WHO
        Eliminating measles and rubella. Framework for the verification process in the WHO European Region.
        World Health Organization Regional Office for Europe, 2014
        • WHO
        Ethiopia | Immunization.
        WHO Regional Office for Africa, 2015 (Available from: http://www.afro.who.int/en/ethiopia/country-programmes/topics/4594-ethiopia-immunization.html. [cited April 05, 2017])
        • WHO
        Measles and rubella surveillance data. WHO-immunization, vaccines and biologicals.
        2018 (Available from: http://www.who.int/immunization/monitoring_surveillance/burden/vpd/surveillance_type/active/measles_monthlydata/en/. [updated 12 June 2018; cited June 25/2018])
        • Yadav S.
        • Gupta S.
        • Kumari S.
        Sero-prevalence of rubella in women of reproductive age group.
        Indian J Pathol Microbiol. 1995; 38: 139-142
        • Zanga Josue
        • Mbanzulu Makola Kennedy
        • Kabasele Arnold-Freddy
        • Ngatu Nlandu Roger
        • Wumba Dimosi Roger
        Rubella Seroprevalence and real-time PCR detection of RUBV among Congolese pregnant women.
        BMC Infect Dis. 2017; 17: 2-7