Effectiveness of a group B OMV meningococcal vaccine against gonorrhoea – the New Zealand experience

Abstract

With increasing multiple drug resistance, vaccination against Neisseria gonorrhoea would have considerable public health benefits. Ecological data from Cuba and NZ suggest a decline in rates of gonorrhoea may occur following the use of group B meningococcal Outer Membrane Vesicle (OMV) vaccines. We evaluated vaccine effectiveness (VE) of the NZ MeNZB™ 3+0 schedule against laboratory confirmed gonorrhoea using two observational studies - a retrospective case-control study of laboratory confirmed clinic diagnoses and cohort study of hospitalisations due to gonorrhoea. Datasets Case control: National Health Index (demographics), sexual health clinics, National Immunisation Register linked using unique identifier. Controls were positive chlamydia test, negative gonorrhoea. Cohort: NZ hospital discharge data, vaccines given and date, travel to and from NZ, demographic variables including gender, ethnicity, month and year of birth. ICD10 coding identified individuals hospitalised for gonorrhoea. Participants Case control NZers born 1984-1998 eligible to receive vaccine, aged 15-30 years during 2004-2014. Cohort* Data available for 667,587 individuals resident in NZ 2004-2015. Analyses Case control: Odds ratio estimated using unconditional logistic regression. VE as % (1-Odds Ratio). Cohort: Cox’s proportional hazard modelling with Firth correction to estimate adjusted relative risks of hospitalisation for vaccinated versus unvaccinated. Covariates included gender, ethnicity, deprivation, age category. Results 14,730 cases and controls (1,241 incidences gonorrhoea, 12,487 chlamydia, 1,002 co-infection). Vaccinated individuals significantly less likely to be cases, 41% vs 49% (adjusted OR 0.69 (95%CI 0.61-0.79). VE estimate for MeNZB™ against gonorrhoea after adjustment for ethnicity, deprivation, geographic area, gender 31% (95% CI 21-39). Vaccinated individuals significantly less likely to be hospitalised with gonorrhoea, RR 0.55, 95% CI 0.38-0.78, P = .0032, corresponds to VE estimate of 45.3% (21.8-61.8). Conclusion Ecological and empirical data support effect of MeNZB™ OMV vaccine on both clinic-diagnosed gonorrhoea infection and hospitalisation. Results may inform development of more effective gonorrhoea vaccines.