Key Points

• After more than two years of low incidence during the COVID-19 pandemic, a resurgence of invasive meningococcal disease (IMD) was observed during the 2022/23 season.

• A peak in incidence was observed in December 2022, particularly during week 52 of 2022. This peak occurred earlier than the seasonal peak observed during pre-pandemic seasons (which typically peaked between January and March, depending on the season). During the first quarter of 2023, the number of IIM cases remained at a high level (particularly in January and March) compared to the incidence observed during the same months in pre-pandemic seasons.

• The resurgence of IIM is not an unexpected phenomenon following two years of low meningococcal circulation. Two hypotheses can be put forward to explain this marked resurgence of IIM:

  • A higher risk of infection resulting from reduced immunity in the population, which was less exposed to meningococci between 2020 and 2022 (barrier measures, social distancing);

  • A more pronounced season linked to the scale of seasonal viral infection outbreaks in 2022/23, particularly influenza virus infections, which can increase the risk of invasive bacterial infections (meningococci, streptococci).

• The situation varies significantly across the country depending on the serogroups. Spatio-temporal clusters of IIM B were identified in 2022 (Auvergne-Rhône-Alpes, Strasbourg), and local vaccination campaigns were implemented among the population. These situations appear to be contained at this time but are being closely monitored. These phenomena can occur randomly in connection with the emergence and local establishment of certain strains of meningococci, which requires very regular monitoring of epidemiological data.

• The resurgence observed during the 2022–2023 season underscores the importance of vaccinating infants to protect them against infections linked to serogroups B and C (recommendations available on the Vaccination Info Service website).

• Santé publique France continues to monitor IIM in collaboration with its partners (ARS, CNR). This reactive surveillance enables the early detection of clusters of cases or unusual situations that may lead to the implementation of local vaccination campaigns in the event of localized excess incidence.