Invasive Meningococcal Disease in Hospitalized Children in Argentina, 2020–2024

BACKGROUND: Invasive meningococcal disease (IMD) is a low-incidence but high-impact infection associated with substantial mortality and sequelae. Following MenACWY vaccine introduction into Argentina's National Immunization Program in 2017, updated data on residual disease burden are needed. METHODS: A multicenter active hospital-based surveillance study was conducted in 6 pediatric sentinel units in Argentina (January 2020-December 2024) in children younger than 15 years with suspected IMD. Cases were confirmed by culture and/or polymerase chain reaction from a normally sterile body site. Hospital discharge rates were calculated per 10,000 discharges. Whole-genome sequencing and genetic Meningococcal Antigen Typing System were used to characterize strains and estimate theoretical 4CMenB coverage. RESULTS: Among 234,264 pediatric hospital discharges, 27 confirmed IMD cases were identified (overall rate: 1.2 per 10,000; 95% confidence interval, 0.8-1.7). Annual rates showed no consistent pattern between children younger than 2 years and those 2 years or older. The case-fatality rate was 14.8% (4/27); all deaths occurred in previously healthy children younger than 5 years and were associated with sepsis and a fulminant course (hospital stay ≤1 day). Of 20 cases with a determined capsular group, 19 (95%) were B and 1 (5%) was C; no capsular group Y or W cases were identified. Theoretical 4CMenB coverage by genetic Meningococcal Antigen Typing System was 77.3%, driven by ST-162 clonal complex predominance. CONCLUSIONS: IMD in Argentina continues to predominantly affect young children and is associated with elevated case-fatality amid fulminant sepsis. Serogroup B predominates in the post-MenACWY era, and high estimated 4CMenB coverage supports evaluation of serogroup B vaccination as a complementary prevention strategy.