Vaccination Against Bacterial Meningitis

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Thanks to conjugate vaccines specially against Haemophilus influenzae (Hib) and Streptococcus pneumoniae (Pnc), bacterial meningitis has become disease whose global importance is no more realized in the affluent countries. However, more than 1 MI individuals a year, proportionally more often children than adults, fall down; one-third succumb, and one-third of survivors are left with moderate-to-severe sequelae. In the world where the meningitis problem is greatest, only a fraction of people are vaccinated. The main (though not only) reason is the too high cost of conjugates for those populations.

Years ago, inexpensive polysaccharide vaccines were developed against Hib, Pnc, and Neisseria meningitidis (Mnc). The Hib, polysaccharide is rightly gone, but all potential of polysaccharides against Pnc and Mnc has not been used. The reasoning is that polysaccharides are not sufficiently immunogenic in small children (in greatest risk). However, convincing clinical efficacy data are lacking to prove this statement. It is unlikely that those data will ever be produced, because people are too convinced of the superiority of conjugates to support any major field trial with a Pnc or Mnc polysaccharide.

At present, variable conjugate vaccines are available against Hib, 7-13 serotypes of Pnc, and up to 4 serogroups of Mnc. Hib vaccination is indicated in all countries. So is also Pnc conjugate, albeit its effect specifically against meningitis depends on local epidemiology (serotype distribution). In case of Mnc meningitis, the main problem is the lack of sufficiently good vaccine against serogroup B, the most common group in many countries. Fortunately, encouraging results have been obtained recently regarding a new-type of vaccine.

Group A Mnc is a special problem of Africa. Monovalent conjugate has been used there, and luckily, its price is tolerable because of its manufacturing outside Big Farma. This approach would be welcome to cover other causative agents of meningits as well.