Recent increase of atypical forms of invasive meningococcal disease

Background: Invasive meningococcal disease (IMD) cases declined upon the implementation of non-pharmaceutical interventions (NPI) to control the COVID-19 pandemic but rebounded since the second half of 2022 in numbers with genotypical changes of the strains. We explored in this report associated modifications in the clinical presentations of IMD. Methods: : We conducted a retrospective descriptive study using the French National Reference Centre Database for meningococci between 2015-2022. We scored serogroups, sex, age groups, clinical presentations and clonal complexes of the corresponding isolates. Findings: Non-meningeal atypical forms of IMD increased significantly upon easing of NPI, such as bacteriemic meningococcal pneumonia and abdominal forms. They represented 6% and 8% of all IMD forms and were significantly linked to serogroups Y and W respectively, to older adults for bacteriemic pneumonia and to young adults for abdominal presentations. These atypical forms were also significantly associated with more early mortality. Interpretation: An upsurge of atypical forms in France since the lifting of COVID-19-related NPI accompanied the rebound of IMD cases. An increase in IMD burden may be expected and urge to enhance preventive strategies against IMD by adapting current vaccination strategies to epidemiological changes.