Key Points

• In 2025, 628 cases of invasive meningococcal disease (IMD) were reported (+2% compared to 2024), confirming the resurgence of IMD observed since 2022.
• The number of cases by serogroup was similar to that observed in 2024, with 279 cases of IIM B (46% of cases with a known serogroup), 178 cases of serogroup W IIM (29% of cases), 143 cases of serogroup Y IIM (23% of cases), and 12 cases due to other serogroups or non-capsulated strains (less than 2% of cases).
• The resurgence of IIM since 2022 is driven by serogroups B, W, and Y. While serogroup B has reached levels slightly higher than those observed before the COVID-19 pandemic, the number of cases caused by serogroups W and Y exceeds previously observed levels.
• The increase in W and Y IIMs in the population underscores the importance of the ACWY vaccination recommended for adolescents and young adults. This strategy aims to provide them with direct protection but also to prevent transmission to other population groups.
• The year 2025 was marked by an exceptional number of cases in January and February 2025, which may be linked to a highly intense 2024/25 flu season.
• In 2025, the incidence rate of reported IIM cases remained highest among infants under one year of age, with 60 cases, representing a rate of 9.7 per 100,000 inhabitants. IIM B and W accounted for nearly all cases in this age group. Vaccination of infants is essential because they are at the highest risk of infection.
• The number of cases of IIM B and IIM W and Y has decreased among children aged 12 to 35 months, which may reflect the positive impact of vaccination with meningococcal B vaccines (recommended since 2022 and mandatory since 2025) and ACWY vaccines (mandatory since 2025).
• Since 2023, the number of IIM cases has been rising among older adults in connection with the spread of IIM W and Y.
• The overall case-fatality rate for IIM was 13%, but it was 21% for IIM W, highlighting the particular severity of infections linked to this serogroup.
• C meningococcal infections remain at very low levels. Since 2023, no cases have been reported in children under 15, demonstrating the positive impact of the combined meningococcal C vaccine.