Critical summary of the BERNI study:
Real-world effectiveness of maternal RSVpreF vaccination in Argentina

Reference Pérez Marc G, Vizzotti C, Fell DB, et al. Real-world effectiveness of RSVpreF vaccination during pregnancy against RSV-associated lower respiratory tract disease leading to hospitalisation in infants during the 2024 RSV season in Argentina (BERNI study): a multicentre, retrospective, test-negative, case–control study. Lancet Infect Dis. 2025;25(9):1044-1054.  Study overview This paper reports the first real-world effectiveness evaluation of maternal RSV prefusion F vaccine (RSVpreF) in Argentina, using a test-negative case-control design across 12 hospitals during the 2024 RSV season.  Methodology assessment  Strengths  Study design: The test-negative case-control design is appropriate and widely accepted for vaccine effectiveness studies, reducing bias from differential healthcare-seeking behavior. The design leverages hospitalized infants with LRTD as both cases (RSV-positive) and controls (RSV-negative), which is methodologically sound.  Data quality: Excellent data verification with 100% verification of outcome-related data and >90% verification of other study variables against source documents. Maternal vaccination status was ascertained from the national vaccine registry, minimizing misclassification bias.  Statistical approach: Sophisticated...