Invasive Meningococcal Disease in Hospitalized Children in Argentina, 2020-2024: Clinical, Epidemiologic and Molecular Findings From a Multicenter Active Surveillance Study.

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.