April Killikelly, Winnie Siu, Nicholas Brousseau
Universal seasonal RSV immunization will substantially reduce RSV associated morbidity in infants and could likely be achieved through both program approaches. At current product list prices, the combined pregnancy-infant program offers better value than a universal mAb program. Jurisdictions should consider local epidemiology, feasibility, cost-effectiveness considerations and equity when selecting a program model.
BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of hospitalization among Canadian infants. In March 2026, the National Advisory Committee on Immunization (NACI) released updated guidance reflecting new evidence on the monoclonal antibodies (mAbs) nirsevimab (Beyfortus®) and clesrovimab (Enflosia) and the RSVpreF pregnancy vaccine (Abrysvo). This article summarizes NACI's updated guidance on protecting infants and children from severe RSV disease.
METHODS: To develop the statement, NACI used its standard evidence-based process, reviewing clinical trial data, real world effectiveness studies, RSV epidemiology, and Canadian cost utility modelling, as well as ethics, equity, feasibility and acceptability considerations, to inform program recommendations.
RESULTS: Both mAbs and the RSVpreF vaccine demonstrated strong protection against RSV related hospitalization, intensive care unit (ICU) admission, and medically attended illness in infants. All products showed favourable safety profiles. The RSVpreF vaccine was effective when administered ≥14 days prior to delivery. Economic modelling indicated that a combined program of RSVpreF vaccination during pregnancy and targeted infant mAb administration offers the best value for money at current product prices. NACI strongly recommends universal seasonal RSV immunization for infants. Jurisdictions may choose either 1) a universal infant mAb program or 2) a combined pregnancy RSVpreF vaccination plus targeted infant mAb administration program. Infants at increased risk of severe RSV disease should receive mAbs regardless of gestational RSVpreF vaccination status.
CONCLUSION: Universal seasonal RSV immunization will substantially reduce RSV associated morbidity in infants and could likely be achieved through both program approaches. At current product list prices, the combined pregnancy-infant program offers better value than a universal mAb program. Jurisdictions should consider local epidemiology, feasibility, cost-effectiveness considerations and equity when selecting a program model.