The monoclonal antibody nirsevimab (Beyfortus) was associated with a lower rate of hospitalization for RSV-related lower respiratory tract infection in the season that it was given.However, during a second year of follow-up, there was no significant association between nirsevimab and RSV-related hospitalization.Nirsevimab was not associated with reduced hospitalizations due to non-RSV infections or asthma.
The monoclonal antibody nirsevimab (Beyfortus) consistently performed well against respiratory syncytial virus (RSV)-related hospitalization during infants' first year after receipt but without a benefit for other hospitalizations or second-year outcomes, a nationwide cohort study from France indicated.
During infants' first year after receipt, nirsevimab's effectiveness estimate against hospitalization for RSV-related lower respiratory tract infection (LRTI) was 66% in a 2023 birth cohort and 72% in a 2024 birth cohort, both statistically significant reductions in risk, reported Amélie Gabet, PhD, of the French National Agency for Medicines and Health Products Safety in Saint-Denis, and colleagues.
The findings answered questions about whether first-year effectiveness -- initially assessed during the RSV A–predominant 2023-2024 season -- would be maintained in the 2024-2025 season after the shift toward RSV B predominance and emergence of RSV B variants carrying resistance-associated mutations, the group wrote in JAMA Pediatrics.
