Highlights
- •Lower severity of illness caused by the SARS-CoV-2 Omicron variant and the efficacy of vaccination generated -82% hospitalizations.
- •Lower severity of illness caused by the SARS-CoV-2 Omicron variant and the efficacy of vaccination generated -84% ICU admissions.
- •Lower severity of illness caused by the SARS-CoV-2 Omicron variant and the efficacy of vaccination contributed to lower SARS-CoV-2 pathogenicity.
Abstract
We retrieved data from the online database of the Italian Ministry of Health concerning the previous and ongoing waves of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic in Italy. We analyzed the prevalence of variants, the number of SARS-CoV-2 diagnoses, hospitalization, and intensive care unit (ICU) admissions for patients with coronavirus disease 2019 (COVID-19). We compared 2 similar days: January 12, in 2021and 2022. Although the number of positive cases in 2022 was nearly fourfold higher compared with the same period in 2021, presumably owing to higher transmissibility of Omicron variant, a considerable decrease of COVID-19 related hospitalizations (-82%) and ICU admissions (-84%) could be observed in the more recent period, when the Omicron variant was largely prevalent and COVID-19 vaccination was widespread.
Keywords
Abbreviations:
SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2), COVID-19 (Coronavirus Disease 2019), ICU (Intensive Care Unit)We read with interest the recent article of Abdullah et al., who concluded that a significantly lower severity of illness associated with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron B.1.1.529 variant-driven epidemic wave had been observed in Tshwane, South Africa (
Abdullah et al., 2021
). This agrees with evidence recently published in other studies from South Africa, the United States, and the United Kingdom (- Abdullah F
- Myers J
- Basu D
- Tintinger G
- Ueckermann V
- Mathebula M
- et al.
Decreased severity of disease during the first global Omicron variant Covid-19 outbreak in a large hospital in Tshwane, South Africa.
Int J Infect Dis. 2021; (Dec 28:S1201-9712(21)01256-XEpub ahead of print)https://doi.org/10.1016/j.ijid.2021.12.357
Mahase, 2021
), which also reported a similar suggestion of decreased pathogenicity associated with this new and highly mutated Omicron lineages (Lippi et al., 2021
).To corroborate these preliminary findings, we retrieved data available in the online database of the Italian Ministry of Health concerning the previous and ongoing waves of the SARS-CoV-2 epidemic in Italy (
Italian Ministry of Health 2022
). We analyzed the prevalence of variants, the number of SARS-CoV-2 diagnoses, hospitalization, and intensive care unit (ICU) admissions for coronavirus disease 2019 (COVID-19). We compared 2 similar days: January 12, 2021, and January 12, 2022, and then analyzed with MedCalc (Version 20.015; MedCalc Software Ltd., Ostend, Belgium). Statistical significance was set at p <0.05. The study was carried out in accordance with the Declaration of Helsinki, under terms of relevant local legislation. This research was based on publicly available data thus Ethical Committee approval was unnecessary.Italian Ministry of Health. Covid-19 - Situazione in Italia. Available at: https://www.salute.gov.it/portale/nuovocoronavirus/homeNuovoCoronavirus.jsp. Last accessed, January 15, 2022.
As listed in Table 1, the total number of Italian citizens who tested positive for SARS-CoV-2 infection on January 12, 2021 (estimated prevalence of SARS-CoV-2 Alpha B.1.1.7 variant: 92%; vaccination rate: <0.1%) and January 12, 2022 (estimated prevalence of SARS-CoV-2 Omicron B.1.1.529 variant: >80%; vaccination rate: 86.6%) was 570,040 and 2,222,060, respectively. Although the number of positive cases in 2022 was nearly fourfold higher compared with the same period in 2021, presumably owing to higher transmissibility of Omicron lineages (
Lippi et al., 2021
), a considerable decrease of COVID-19 related hospitalizations (-82%) and ICU admissions (-84%) could be observed in the more recent period, when the Omicron lineages were largely prevalent and COVID-19 vaccination was widespread (Table 1). Notably, the infection rate in January 2022 was 3,569 per 100,000 in unvaccinated people compared with 1,770 per 100,000 in vaccine recipients, thus translating into a cumulative vaccine efficiency against this endpoint of 52% (Odds ratio, 0.48; 95% CI, 0.46-0.51; p <0.001).Table 1Number of SARS-CoV-2-positive Italian citizens and COVID-19related hospitalization and intensive care unit (ICU) admissions during 2 different epidemiologic waves
| Endpoint | January 12, 2022 | January 12, 2021 | Odds ratio (and 95% CI) |
|---|---|---|---|
| Total cases | 2,222,060 | 570,040 | - |
| Predominant variant | B.1.1.529 (Omicron; >80%) | B.1.1.7 (Alpha; 92%) | - |
| Vaccination coverage | 86.6% | <0.1% | - |
| Hospitalizations | 17,309 (0.78%) | 23,712 (4.16%) | 0.18 (95% CI, 0.18-0.18; p <0.001) |
| ICU admissions | 1,669 (0.08%) | 2,636 (0.46%) | 0.16 (95% CI: 0.15-0.17; p <0.001) |
95% CI = 95% confidence interval; OR =odds ratio.
Reviewed together, these Italian data agrees with data reported in other countries, suggesting that the efficacy of vaccination combined with ostensibly lower severity of illness caused by the Omicron B.1.1.529 variant may substantially mitigate some of the pressure of COVID-19 on healthcare systems faced with a massive surge in cases also involving unvaccinated and immunodeficient populations.
Conflict of interest
The authors declare no conflict of interest.
Funding
This work received no funding.
Acknowledgments
None.
Authors’ contribution
Study design: GL, CM, BMH; Data Collection: GL, CM; Data analysis: GL, BMH; Writing: GL, BMH
Ethical Approval
Unnecessary (electronic search on a freely available database).
References
- Decreased severity of disease during the first global Omicron variant Covid-19 outbreak in a large hospital in Tshwane, South Africa.Int J Infect Dis. 2021; (Dec 28:S1201-9712(21)01256-XEpub ahead of print)https://doi.org/10.1016/j.ijid.2021.12.357
Italian Ministry of Health. Covid-19 - Situazione in Italia. Available at: https://www.salute.gov.it/portale/nuovocoronavirus/homeNuovoCoronavirus.jsp. Last accessed, January 15, 2022.
Lippi G, Mattiuzzi C, Henry BM. Updated picture of SARS-CoV-2 variants and mutations. Diagnosis (Berl). 2021 Dec 23. doi: 10.1515/dx-2021-0149. Epub ahead of print.
- Covid-19: Hospital admission 50-70% less likely with omicron than delta, but transmission a major concern.BMJ. 2021; 375: n3151
Article info
Publication history
Published online: March 08, 2022
Accepted:
March 5,
2022
Received in revised form:
March 1,
2022
Received:
January 5,
2022
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© 2022 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.
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