Background: Observational data suggest a possible effect of outer membrane vesicle (OMV) meningococcal group B vaccines on incidence of gonorrhoea. We evaluated the vaccine effectiveness (VE) of tailor made OMV meningococcal B vaccine (MeNZB™) against confirmed gonorrhoea cases among adolescents and adults aged 15-30 years.
Methods: A retrospective case-control study of patients born between 1984 and 1998 eligible to receive the vaccine and between 15 and 30 years of age during the study period 2004 to Jan 2016. Demographic data, sexual health clinic data and the National Immunisation Register were linked using a unique identifier. For primary analysis cases were confirmed by laboratory isolation or detection of N. gonorrhoeae from a clinical specimen, controls were a positive chlamydia test including co-infection. An odds ratio was estimated using conditional logistic regression. VE as a percent was calculated as 100*(1-Odds Ratio).
Results: There were 12,725 cases and controls for analysis from eight participating sexual health clinics between 2004 and Jan 2016. These consisted of 867 diagnoses of gonorrhoea and chlamydia co-infection, 10,833 of confirmed chlamydia and 1,025 diagnoses of gonorrhoea. Ethnicity, deprivation and gender had a significant association with gonorrhoea diagnosis with Mâori, Pacific Peoples more likely than Europeans to be cases. Males and those of higher deprivation were more likely to be cases. Vaccinated individuals were significantly less likely to be cases (Adjusted OR 0.71 95% CI 0.62-0.81). The estimate for effectiveness of the NZ OMV meningococcal vaccine against gonorrhoea after adjustment for ethnicity, deprivation and gender is 29% (95% CI 19-38).
Conclusions: The NZ OMV meningococcal vaccine was associated with moderate cross protection against a gonorrhoea diagnosis. This observation may provide insights into mechanisms for protection against N. gonorrhoeae associated disease. A vaccine that provides even moderate protection may be beneficial, particularly as antimicrobial resistance has become a growing international problem.