A Multidesign Study of 4CMenB Vaccine Effectiveness and Impact on Meningococcal Carriage and Gonorrhea in Northern Territory Adolescents and Young People

Background: . 4CMenB has an impact on unencapsulated meningococcal oropharyngeal carriage, where outer membrane proteins are exposed, potentially exerting selective pressure on these strains. We assessed the impact of 4CMenB immunization on gonorrhea disease and oropharyngeal meningococcal carriage among adolescents in the Northern Territory (NT), Australia. Methods: All adolescents aged 14-19 years in the NT were eligible to receive two doses of 4CMenB between 2021 and 2023. Participants had oropharyngeal swabs collected at baseline and 12 months. Vaccine effectiveness (VE) against gonorrhea was assessed using linked notification and immunization data. A Cox proportional hazards model stratified by sex, age, and geography estimated VE. Mixed-effects logistic regression estimated postvaccination odds of meningococcal carriage. Results: A total of 30 650 adolescents were included in the VE analysis, with 9.6% receiving 2 doses of 4CMenB, and 42.4% of the population identifying as Aboriginal or Torres Strait Islanders. Gonococcal notifications were reduced in vaccinated adolescents (VE 38.4%, 95% CI: 18.6-53.4). Overall, meningococcal carriage increased from 4.0% to 6.2% (OR 1.68, 95% CI: 1.14-2.48), driven by genogroup B and nongroupable strains. Carriage of disease-associated meningococci remained stable. Conclusions: 4CMenB confers modest protection against gonorrhea in a real-world setting with higher adolescent disease prevalence. These findings are important for women, considering infections are often asymptomatic and have the potential for serious complications. The NT has now introduced a 4CMenB infant and adolescent program.