The University of Adelaide
Impact of MenB vaccine on meningococcal disease and carriage of Neisseria meningitidis in South Australian adolescents
Neiseria meningitidis is the cause of invasive meningococcal disease, primarily affecting young children and adolescents. Exposure to N. meningitidis is common in the general population, leading to asymptomatic pharyngeal carriage with highest carriage prevalence in adolescents. 4CMenB (Bexsero®) is a recombinant protein-based vaccine licensed to protect against invasive group B meningococcal disease, but its role in preventing transmission by impacting on carriage and inducing population protection is uncertain.
In a cluster randomized controlled trial, 237 schools in South Australia were randomised to 4CMenB vaccination at baseline (intervention) or 12 months (control), for year 10-12 students (aged 15-18 years). Primary outcome was oropharyngeal carriage of disease-causing N. meningitidis (groups A,B,C,W,X,Y) in year 10/11 students, identified by both porA and genogroup PCR assays. Risk factors for carriage were assessed at baseline. During April-June 2017, 24,269 year 10/11 students and 10,220 year 12 students were enrolled in the study. At 12 months, there was no difference in carriage prevalence of disease-causing N. meningitidis between vaccinated (2.55%; 326/12746) and control (2.52%; 291/11523) students (aOR =1.02; 95%CI 0.80, 1.31; p=0.85). At baseline, significant risk factors for carriage of disease-causing N. meningitidis included year of schooling, current upper respiratory tract infection, smoking cigarettes, smoking a water-pipe, attending pubs/clubs and recent intimate kissing. Carriage prevalence of all N. meningitidis in Aboriginal adolescents was twice that of non-Aboriginal adolescents (6.8% vs 3.4%). In an exploratory post-hoc analysis, a 29% reduction in non-typeable N. meningitidis was identified in the vaccinated group compared to control group (1.65% vs 2.23%; aOR=0.71; p=0.008). Acquisition of invasive genogroups was the same in vaccinated (2.1%) and unvaccinated (2.1%) groups. Vaccine impact against all meningococcal disease in adolescents 17-19 years of age was 71.4% (95%CI 29.0%, 96.3%).
4CMenB protected against meningococcal disease but did not impact on carriage of disease causing N. meningitidis. Therefore 4CMenB immunisation strategies should focus on direct (individual) protection against invasive group B meningococcal disease. A MenB vaccine program has been introduced in South Australia based on direct protection in age groups with highest rates of disease.
Professor Marshall is a medical researcher and NHMRC Practitioner Fellow. She is Professor in Vaccinology in the Adelaide Medical School and is the Deputy Director, Clinical and Translational Research of the Robinson Research Institute at the University of Adelaide, Senior Medical and Public Health Practitioner and Director of the Vaccinology and Immunology Research Trials Unit at the Women’s and Children’s Hospital. She has been a member of the Australian Technical Advisory Group on Immunisation and has a research program in vaccine preventable diseases and prevention through immunisation. In recognition of her research leadership and translation she was awarded NHMRC “10 of the Best” in 2016, the South Australia Science Award for Excellence in Research for the Public Good in 2011 and Excellence in Research Collaboration in 2019. See https://researchers.adelaide.edu.au/profile/helen.marshall.