NACI update: A new tool to protect infants from RSV

The National Advisory Committee on Immunization (NACI) recommends adding clesrovimab to the arsenal for preventing respiratory syncytial virus (RSV) in infants and young children. This monoclonal antibody was approved by Health Canada in February 2026.After reviewing the evidence, NACI strongly recommends offering nirsevimab or clesrovimab to all infants during their first RSV season, as well as to infants who remain at high risk during their second RSV season.With a high degree of certainty, clesrovimab has demonstrated potential efficacy in preventing hospitalizations due to respiratory tract infection caused by RSV. During the first RSV season, the monoclonal antibody also shows potential efficacy in preventing admissions to intensive care units, with a moderate degree of certainty.In general, clesrovimab was well tolerated in newborns, whether term or preterm; it caused similar adverse events to the placebo group.Like nirsevimab, clesrovimab is contraindicated in infants with a history of severe hypersensitivity reactions, including anaphylaxis, to any component of the product. Both clesrovimab and nirsevimab can be administered on the same day as systemic childhood vaccines.Protection for the first seasonCurrently, clesrovimab can only be administered during the first year of life. It has been approved for the prevention of lower respiratory tract infections (LRTIs) caused by RSV in newborns and infants born during RSV season or who are experiencing their first RSV season. It is “not authorized for infants and children at ongoing risk during their second RSV season.” However, “its off-label use could be considered,” the NACI states.Clinical trials currently underway in immunocompromised infants and children under 24 months of age are aimed at establishing the efficacy and safety of clesrovimab for a second RSV season.Real-world data on nirsevimabThe NACI also took the opportunity to update its recommendations on currently available immunizing agents.Since the approval of nirsevimab and RSpreF in 2023, data on their real-world effectiveness have accumulated. A meta-analysis of 32 observational studies shows an 83% reduction (95% CI: 77% to 88%) in RSV-related hospitalizations and an 81% reduction (95% CI: 71% to 88%) in intensive care unit admissions among children who received nirsevimab during their first RSV season. These data are consistent with those from the clinical trials that led to the approval of the monoclonal antibody.Regarding maternal vaccination with RSVpreF, real-world data point to increased protection against serious consequences attributable to RSV. According to the cohorts studied, vaccination administered at least 14 days before delivery reduced RSV-related hospitalizations by up to 82% (95% CI: 75.1% to 87.3%) and intensive care unit admissions by up to 87% (95% CI: 52.6% to 97.0%).Following a review of the evidence, the NACI therefore maintains its recommendation to implement a universal RSV immunization program to protect infants.A combined program of vaccine administration during pregnancy and monoclonal antibody administration in infants may also be considered by public health authorities.This article has been translated from its original French and first appeared on our sister site Profession Santé.

NACI update: A new tool to protect infants from RSV

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