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The problem
Intervention: Nirsevimab immunization, a monoclonal antibody against RSV, administered to all infants and high-risk children under 24 months
Who it was tested with: Children under 24 months presenting to a pediatric emergency department with bronchiolitis across two consecutive RSV seasons (n=484; 336 in season 1, 148 in season 2).
The same group is measured before the intervention and again afterwards, with a baseline and an endline and sometimes a midline. Change is visible, but other causes cannot be ruled out.
"A retrospective single-center cohort study was conducted to evaluate the impact of nirsevimab introduction on bronchiolitis epidemiology in an Italian tertiary pediatric ED...All children < 24 months who presented to our ED with bronchiolitis during two consecutive RSV seasons...were included." The study measures the same population across two consecutive seasons before and after intervention introduction, though without a formal comparison group.
Single-center design limits generalizability. Retrospective cohort design without a comparison group of unimmunized children makes it difficult to disentangle the effect of immunization from other seasonal and environmental factors. Changes in testing practices or viral circulation patterns are not ruled out.
Across countries and designs
3 studies · 1 country
