Laura V Cooper, Medard Djedanem, Assan Abdoul Nasser, Khalidou Moussa, Kourouma Mamadou, Camara Ibrahima, Mahamadou Doutchi, Joaquin Baruch, Katya Fernandez, Anderson Latt, Clement Lingani, Andre Bita, Isha Berry, Todd Swarthout, Ousmane Guindo, Lorenzo Pezzoli, Elhadji Ibrahim Tassiou, Matthew Coldiron
NmCV-5 demonstrated high effectiveness against circulating meningococcal strains NmC and NmW in real-world outbreak conditions. Limitations include small sample size, reliance on self-reported vaccination status, and absence of cases from other serogroups. Further studies should assess long-term impact on carriage and effectiveness against invasive disease across all targeted serogroups.
BACKGROUND: Meningococcal meningitis remains a major public health challenge in Africa's meningitis belt despite the successful elimination of serogroup A epidemics following MenAfriVac introduction. Outbreaks caused by serogroups C, W, and X persist. NmCV-5, a pentavalent conjugate vaccine targeting serogroups A, C, W, Y, and X, was prequalified by WHO in 2023 and used in Niger during reactive vaccination campaigns in 2024.
METHODS: We conducted a matched case-control study in six health districts in Niger (Niamey IV and Magaria) to estimate NmCV-5 effectiveness against meningococcal meningitis. Cases were individuals with PCR-confirmed meningococcal meningitis, aged 1-19 years, resident in the vaccination campaign area, and presenting with symptom onset ≥10 days post-campaign. Enrollment took place between May 2024 and July 2025. Four age-, sex-, and residence-matched community controls were enrolled per case. Vaccination status was verified by patient-retained vaccination card when available or self-reported. Logistic regression was used to calculate crude and adjusted vaccine effectiveness (VE).
RESULTS: 17 confirmed cases (14 NmC, 3 NmW) and 68 matched community controls were enrolled in the study. Seven cases (41%) and 58 controls (86%) reported NmCV-5 vaccination; vaccination status of all cases and 8 of 58 (14%) controls was confirmed by vaccination card. Crude VE against all meningococcal meningitis was 88% (95% CI: 62-96), and against NmC specifically was 86% (95% CI: 50-96). Adjusted for household crowding and history of recent respiratory infections, VE was 92% (95% CI: 72-98) overall and 91% (95% CI: 63-98) for NmC. Sensitivity analyses confirmed robustness of estimates under extreme assumptions.
CONCLUSIONS: NmCV-5 demonstrated high effectiveness against circulating meningococcal strains NmC and NmW in real-world outbreak conditions. Limitations include small sample size, reliance on self-reported vaccination status, and absence of cases from other serogroups. Further studies should assess long-term impact on carriage and effectiveness against invasive disease across all targeted serogroups.