Invasive Meningococcal Disease in Adults Aged ≥65 Years Admitted to French Intensive Care Units: A Nationwide Comparison With Younger Adults

BACKGROUND: Invasive meningococcal disease (IMD) is traditionally associated with younger populations, but its impact on older adults is rising. We aimed to describe the clinical characteristics and outcomes of critically ill older patients with IMD and identify risk factors for in-hospital mortality. METHODS: We conducted an ancillary analysis of the French nationwide multicenter RETRO-MENINGO cohort (2016-2024). All adults admitted to 102 ICUs with microbiologically confirmed IMD were included and stratified by age (≥65 vs. <65 years). The primary outcome was all-cause in-hospital mortality. Multivariable logistic regression identified factors independently associated with death. RESULTS: Among 654 patients, 114 (17%) were aged ≥65 years, of whom only 0.9% were reported as vaccinated. Compared to younger adults, older patients presented more frequently with hemodynamic failure and less often with classic purpura or meningeal symptoms. Serogroup W predominated in the older group, while serogroup B was more common in younger patients. Older adults required more organ support and had significantly higher in-hospital mortality (28.1%, n=32/114 vs. 9.6%, n=52/540 p<0.001). After adjustment, age ≥65 years remained independently associated with in-hospital mortality (aOR 2.99; 95% CI 1.57-5.72; p<0.001), while administration of a third-generation cephalosporin before ICU admission was protective (aOR 0.45; 95% CI, 0.24-0.84; p=0.01). CONCLUSIONS: Critically ill older adults with IMD exhibit atypical clinical features, a high prevalence of serogroup W, and nearly triple the in-hospital mortality of younger patients. These findings emphasize the need for high clinical suspicion, rapid antibiotic therapy, and potential expansion of vaccination strategies to include older populations.