A group B meningococcal outer-membrane-vesicle (OMV) vaccine used during a meningitis outbreak in New Zealand also protected against gonorrhea, according to a report published online July 10 in the Lancet.
Even though Neisseria meningitidis and Neisseria gonorrhoeae cause distinctly different diseases, the bacteria are closely related and are genetically and antigenically very similar. Most of the virulence factors present in one pathogen have an equivalent in the other, “providing at least one biologically plausible mechanism for cross-protection,” said Helen Petousis-Harris, PhD, of the department of general practice and primary health care, University of Auckland (New Zealand), and her associates.
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Approximately 1 million people – 81% of the New Zealand population younger than 20 years – received almost 3 million doses of the OMV meningococcal B vaccine (MeNZB) in a 2-year mass immunization program during the outbreak, allowing the investigators to compare the rate of gonorrhea between vaccinated and unvaccinated people. They performed a retrospective case-control study involving 14,730 participants, using information from a national health care database, a national immunization registry, and 11 sexual health clinics covering diverse geographic regions. This included 1,241 cases of gonorrhea (cases), 12,487 cases of chlamydia (controls), and 1,002 cases of gonorrhea plus chlamydia coinfection (categorized as controls or cases in separate analyses).
“The adjusted estimate for vaccine effectiveness of the MeNZB against confirmed cases of gonorrhea” was 31% (95% confidence interval, 21-39; P less than .0001), a finding that remained robust across several sensitivity analyses, Dr. Petousis-Harris and her associates said (Lancet. 2017 July 10. doi: 10.1016/S0140-6736(17)31449-6).
“To our knowledge, ours is the first study to show an association between a vaccine and a reduction in the risk of gonorrhea,” they noted. “The potential ability of an OMV group B meningococcal vaccine to provide even modest protection against gonorrhea would have substantial public health benefits in view of the prevalence of gonorrhea. Modeling suggests that a vaccine with 30% efficacy could decrease the prevalence of gonorrhea by more than 30% within 15 years, if immunity is maintained.”
These findings also are important in view of the organism’s increasing resistance to existing antibiotics. Moreover, if further study confirms that the MeNZB vaccine offers some degree of cross-protection against gonorrhea, these data can inform the development of a gonorrhea vaccine, the investigators added.
This study was funded by GlaxoSmithKline Vaccines and Auckland UniServices. Dr. Petousis-Harris reported serving as a consultant for GSK, Merck, and Pfizer, and one of her associates reported ties to Novartis Vaccines, GSK, Protein Sciences, and Merck.