Flashtalk 25th International Pathogenic Neisseria Conference 2026

From meningitis to gonorrhoea: Long-term population impact of the 4CMenB program in South Australia (#104)

Bing Wang 1 2 , Lynne Giles 3 , Prabha Andraweera 1 2 , Mark McMillan 1 2 , Rebecca Beazley 4 , Paul Young 4 , Sara Almond 4 , Noel Lally 4 , Charlotte Bell 4 , Louise Flood 4 , Peter Richmond 5 6 , James Ward 7 , Helen Marshall 1 2
  1. Robinson Research Institute and School of Medicine, College of Health , Adelaide University, Adelaide, South Australia, Australia
  2. Vaccinology and Immunology Research Trials Unit, Women’s and Children’s Health Network, Adelaide, South Australia, Australia
  3. School of Public Health, College of Health , Adelaide University, Adelaide, South Australia, Australia
  4. Communicable Disease Control Branch, SA Health, Adelaide, South Australia, Australia
  5. School of Medicine and The Kids Research Institute Australia, University of Western Australia, Perth, Western Australia, Australia
  6. Perth Children’s Hospital, Perth, Western Australia, Australia
  7. UQ Poche Centre for Indigenous Health, University of Queensland, Brisbane, Queensland, Australia

Background

Meningococcal disease and gonorrhoea are caused by closely related bacteria (Neisseria meningitidis and Neisseria gonorrhoeae) sharing 80–90% genetic homology. The 4CMenB vaccine (Bexsero®), containing outer membrane vesicles and recombinant antigens (NHBA/NadA/fHBP), was developed to prevent meningococcal B (MenB) disease. Publicly funded 4CMenB programs have been implemented in South Australia since 2018. We evaluated vaccine effectiveness (VE) against MenB disease and gonococcal infection six to seven years post-implementation, using case-control and cohort study designs.

Methods

Gonococcal notifications (cases) and chlamydia notifications (controls) were linked to the Australian Immunisation Register. A time-to-infection analysis among gonococcal cases used multivariable Cox proportional hazards models. For MenB disease, 20 AIR controls were randomly selected to estimate VE. VE was calculated as (1 − odds ratio) ×100%.

Results

Seven years after program introduction, VE against MenB disease was 57.2% (95%CI: −39.9% to 86.9%; p=0.160) for three doses in children and 85.3% (95%CI: 48.0% to 95.9%; p=0.003) for two doses in adolescents. Among MenB cases in children eligible for MenB vaccination, 8 out of 23 cases (35%) occurred in Aboriginal children.

At six years, VE of the two-dose schedule against gonococcal infection in adolescents born between February 1999-January 2010 was 40.2% (95%CI: 33.7% to 46.1%; p<0.001). Evidence of waning was observed at five years post-vaccination (4.1%; 95% CI: −17.8% to 21.9%; p=0.690) compared with within five years (44.4%; 95%CI: 37.7% to 50.4%; p<0.001). VE against subsequent gonococcal infection was 32.9% (adjusted hazard ratio [aHR] 0.671; 95%CI: 0.513-0.878; p=0.004). Chlamydia co-infection was associated with increased risk of subsequent gonococcal infection (aHR 1.881; 95%CI: 1.445-2.449; p<0.001). There was no reduction in risk of a third episode observed (aHR 0.701; 95%CI: 0.442-1.110; p=0.130).

Conclusions

The 4CMenB program demonstrates sustained protection against MenB disease in adolescents at seven years post-implementation, although effectiveness in children against all IMD was not statistically significant. Aboriginal children were disproportionately affected.  Genomic studies will assess strain–vaccine match, and ongoing evaluation is warranted to determine whether booster strategies are required in high-risk groups. Moderate protection against gonococcal infection was observed in the adolescent/young adult population, with evidence of waning five years post-vaccination.