Oral Presentation 25th International Pathogenic Neisseria Conference 2026

Repeat cross-sectional surveillance of meningococcal carriage in South Australia during established MenB and MenACWY vaccination programs (140987)

Mark McMillan 1 2 , Andrew Lawrence 2 , Mark Turra 3 , Rosa Coldbeck-Shackley 3 , Thomas Sullivan 4 , Charlene Kahler 5 , Jeremy Carr 6 , Martin Maiden 7 , Helen Marshall 1 2
  1. Vaccinology and Immunology Research Trials Unit, Women’s and Children’s Health Network, , Adelaide, South Australia, Australia
  2. Adelaide University, Adelaide, South Australia, Australia
  3. SA Pathology, Adelaide, South Australia, Australia
  4. South Australian Health and Medical Research Institute, Adelaide, South Australia
  5. University of Western Australia, Perth, Western Australia
  6. Monash Children’s Hospital, Melbourne, Victoria
  7. University of Oxford, Oxford, United Kingdom

Background
Adolescent meningococcal vaccination programs may alter the ecology of Neisseria meningitidis carriage, with implications for transmission and herd protection. In South Australia, during the early years of the MenB and MenACWY school immunisation programs, carriage of disease-associated meningococci among school leavers remained stable: 5.5% in 2018, 5.0% in 2019, and 5.1% in 2020. Genogroup B carriage increased from 2.1% to 3.2% over the same period (adjusted odds ratio 1.5, 95% CI 1.0 to 2.3). In contrast, 4CMenB has been associated with reduced carriage of non-groupable meningococci, raising the possibility that changes in these strains could affect naturally acquired immunity and broader meningococcal population dynamics. As the South Australian adolescent MenB program enters its eighth year, the longer-term effects of established MenB programs on meningococcal carriage remain uncertain.

Methods
This repeat cross-sectional observational study assesses meningococcal carriage among South Australians aged 17–25 years from 2026-29. Participants are recruited primarily through universities. Following consent, participants complete a risk factor questionnaire and undergo oropharyngeal swabbing. Swabs are placed into STGG transport medium for batched PCR testing. All samples undergo PCR targeting porA and ctrA, with genogroup-specific PCR and bacterial culture performed for positive samples. Viable isolates undergo whole genome sequencing. Analyses will compare 2026 carriage prevalence with 2018–2020 data and assess associations with 4CMenB and MenACWY vaccination, genomic diversity, and behavioural risk factors.

Results
To date, 664 participants have been recruited in 2026. Mean age is 18.9 years, 60% are female, 4.5% report cigarette smoking, 52% have received at least one MenACWY dose, and 45% have received two MenB doses. Historical comparison data from 2018–20 included 8,132 participants, with overall carriage of 9%. Of 156 swabs tested to date, 9 (6%) have had porA and/or ctrA detected. Updated estimates from approximately 1,000 participants, including overall carriage and genogroup distribution, will be presented.

Conclusions
This study will provide updated evidence on meningococcal carriage eight years after the commencement of South Australia’s adolescent MenB and MenACWY vaccination programs. Comparison with 2018–2020 data will help clarify whether program maturity has altered meningococcal carriage dynamics.