Key Points

• In 2024, 616 cases of invasive meningococcal disease (IMD) were reported (+10% compared to 2023), marking the highest annual number of cases since 2010 and confirming the resurgence of invasive meningococcal disease (IMD) observed since 2022.

• The distribution of serogroups was similar to that in 2023: 269 IIM B (45% of cases with known serogroup), 166 IIM W (28%), 141 IIM Y (24%), and 12 IIM C (2%).

• The age groups most affected varied by serogroup:

  • IIM B: higher incidence rates among infants and young children aged 1 to 4 years, and to a lesser extent among young adults aged 15–24 years;

  • IIM W and Y: higher incidence rates among infants and the elderly (≥ 80 years);

• IIM C remained at very low levels, due to high vaccination coverage of infants against meningococcal C and herd immunity in the population;

• IIM W cases were characterized by high case fatality rates (16%) and were associated with two expanding clonal complexes (cc 11 and cc 9 316) in France;

• Compared to the pre-pandemic period (2016–2019), the number of IIM B cases decreased among infants aged 6 to 23 months. The risk of IIM B remains high in this age group among unvaccinated children, which underscores the need to continue efforts to improve meningococcal B vaccination coverage among infants.

• On the other hand, an increase in IIM has been observed among older adults, primarily associated with serogroups W and Y.