Oral Presentation 25th International Pathogenic Neisseria Conference 2026

Vaccine Effectiveness of a Pentavalent Meningococcal Conjugate Vaccine (Men5CV) Used in Response to an Outbreak in Nigeria: A Matched Case-Control Study (140506)

Isha Berry 1 2 , Emmanuel Eze 3 , Fatima Saleh 3 , Ahmed Ladan Mohammed 3 , Abdulmumin Hashim Bala 4 , Bala Buratai 3 , Farida Ciroma 3 , Chinwendu Achugamonye 4 , Celestine Ameh 4 , Ifeanyi Abali 3 , Michael Popoola 3 , Olajumoke Babatunde 3 , Gandi Ajibji Yiga 5 , Abdu Saleh Garba 5 , Bile Nuhu 6 , David L. Karatu 6 , Kabiru Hassan Bajoga 6 , Samaila Mamuda 7 , Sani Ibrahim 7 , Mahmoud Abdulwahab 7 , Isyaka Mohammed Mohammad 8 , Umar Haruna 8 , Oladipupo Ipadeola 9 , Nnenna Ananaba 9 , Ugochi Ezenwelu 9 , Farah Husain 9 , Veronica Pinell-McNamara 10 , Lucy A. McNamara 10 , John Neatherlin 10 , Muhammad S. Balogun 4 , Jide Idris 3
  1. University of Toronto, Toronto, Canada
  2. Infectious Diseases Program, CDC Foundation, Atlanta, USA
  3. Nigeria Centre for Disease Control and Prevention, Abuja, Nigeria
  4. African Field Epidemiology Network (AFENET) Nigeria, Abuja, Nigeria
  5. Bauchi State Ministry of Health, Bauchi, Nigeria
  6. Gombe State Ministry of Health, Gombe, Nigeria
  7. Jigawa State Ministry of Health, Dutse, Nigeria
  8. Yobe State Ministry of Health and Human Services, Damaturu, Nigeria
  9. Division of Global Health Protection, U.S. Centers for Disease Control and Prevention, Abuja, Nigeria
  10. Division of Bacterial Diseases, U.S. Centers for Disease Control and Prevention, Atlanta, USA

Background: Nigeria was the first country to deploy Men5CV—a pentavalent meningococcal conjugate vaccine targeting serogroups A, C, W, X, and Y—in response to a seasonal meningococcal disease outbreak. During the 2023-2024 meningitis season, reactive vaccination campaigns with Men5CV were conducted across 12 local government areas (LGAs) in four northern states, achieving administrative coverage of 47-115%. In the 2024-2025 meningitis season, new suspected bacterial meningitis cases were reported in Nigeria, including in LGAs previously targeted by Men5CV. We describe the epidemiological characteristics of these new cases and estimate vaccine effectiveness of Men5CV against laboratory-confirmed meningococcal disease.

Methods: During the 2024-2025 meningitis season, enhanced bacterial meningitis surveillance was conducted in the 12 LGAs that had implemented Men5CV campaigns. CSF from suspected cases was tested by PCR to confirm presence of Neisseria meningitidis and determine serogroup. Laboratory-confirmed cases were enrolled into a case-control study if they had been eligible for vaccination during the Men5CV campaign (i.e., aged 1-29 years, residing in targeted LGA). For each case, four community controls were recruited, matched by age group and village of residence. Men5CV vaccination status was self-reported and verified through vaccination cards, when available. Descriptive analyses were conducted and vaccine effectiveness was estimated using conditional logistic regression.

Results: Between 1 October 2024 and 30 June 2025, 109 suspected bacterial meningitis cases were identified among individuals eligible for vaccination. The mean age of cases was 13.5 years (SD: 6.7); the majority were male (64.2%, 70/109) and from Jigawa State (53.2%, 58/109). Of the 109 suspected cases, 50 (45.9%) had CSF specimens tested; 26 (52.0%) were confirmed as N. meningitidis. Most confirmed cases were caused by serogroup C (80.8%, 21/26), with serogroups W (11.5%, 3/26) and X (7.7%, 2/26) also reported. Of the 26 confirmed cases, 24 were matched to 96 controls. Vaccination coverage was lower among cases (16.7%, 4/24) than controls (43.8%, 42/96). The adjusted vaccine effectiveness of Men5CV was 83.7% (95% CI: 30.1-96.2, p=0.005).

Conclusions: This analysis provides the first real-world estimate of Men5CV effectiveness. Despite a limited sample size, our findings demonstrate that Men5CV is protective against meningococcal disease, supporting its use in similar contexts.