Summary of NACI statement of April 10, 2026: Updated guidance to protect infants and children from respiratory syncytial virus (RSV) disease: Use of monoclonal antibodies (nirsevimab and clesrovimab) and the RSVpreF vaccine

Date published: April 10, 2026

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• Overview
• What you need to know

Overview

On April 10, 2026, the Public Health Agency of Canada (PHAC) released the National Advisory Committee on Immunization’s (NACI) Updated guidance to protect infants and children from respiratory syncytial virus (RSV) disease: Use of monoclonal antibodies (nirsevimab and clesrovimab) and the RSVpreF vaccine. This guidance is based on current evidence and NACI expert opinion.

There are now four products to protect infants and young children from RSV:

• Palivizumab (SYNAGIS, Astrazeneca) is a monoclonal antibody authorized to protect infants at high risk in their first and second RSV season.
• Nirsevimab (BEYFORTUS, Sanofi) is a long-acting monoclonal antibody authorized to protect all infants in their first RSV season and children under 24 months of age who remain vulnerable to severe RSV disease in their second RSV season.
• Clesrovimab (ENFLONSIA, Merck) is a long-acting monoclonal antibody authorized to protect all infants in their first RSV season.
• RSVpreF (ABRYSVO, Pfizer) is a vaccine authorized to protect infants through vaccination during pregnancy.

Following a thorough review of the evidence, NACI makes the following recommendations for public health program decision-making (i.e., provinces/territories making decisions for publicly funded immunization programs):

• NACI strongly recommends universal RSV immunization programs to protect infants, using seasonal administration.
• NACI strongly recommends that jurisdictions implement a seasonal RSV immunization program, based on local context, feasibility and program priorities:
  • Infant monoclonal antibody program
    • Offering nirsevimab or clesrovimab to all infants during their first RSV season and to infants at continued high risk during their second RSV season.
  • Combined pregnancy vaccine and infant monoclonal antibody program
    • Offering RSVpreF during pregnancy to protect infants born during the RSV season.
    • Offering nirsevimab or clesrovimab to infants who are at increased risk of severe RSV disease, including infants born to women or individuals who received RSVpreF vaccine during pregnancy.
    • Offering nirsevimab or clesrovimab to infants who are born to women or individuals who did not receive the RSVpreF vaccine during pregnancy, regardless of underlying risk status, or who are born less than 2 weeks after RSVpreF administration.
• NACI strongly recommends that infants at increased risk of severe RSV disease receive monoclonal antibodies.

For more information on which groups are considered to be at increased risk of severe RSV disease, please see List 1 in the NACI statement.

For the full statement, refer to: Updated guidance to protect infants and children from respiratory syncytial virus (RSV) disease: Use of monoclonal antibodies (nirsevimab and clesrovimab) and the RSVpreF vaccine (PDF).

What you need to know

• Respiratory syncytial virus (RSV) is one of the most common respiratory viruses in infants and young children, infecting almost all children in Canada by two years of age. Although infants with certain underlying medical conditions are at increased risk of severe disease, the majority of infants hospitalized with RSV each year are otherwise healthy.
• Prevention strategies for RSV have evolved in recent years with the authorization of new immunization products to protect infants from severe RSV disease, including long-lasting monoclonal antibodies (nirsevimab, clesrovimab) and a vaccine given during pregnancy (RSVPreF).
• In this update, NACI continues to recommend a universal RSV program to protect all infants. This update was initiated by the addition of clesrovimab, a new monoclonal antibody authorized in Canada, and updated effectiveness and safety data on RSV immunization products to protect infants from severe RSV disease.
• All authorized RSV immunization products have evidence to demonstrate the ability to prevent severe RSV disease and meet high safety standards.
• RSV is a seasonal virus, with infections being more common in the winter. Therefore, nirsevimab and clesrovimab, should be given at the start of the RSV season since protection takes effect immediately. RSVpreF should be given before the start of the RSV season to allow protection to develop following vaccine administration.
• NACI recommends that RSVpreF can be given from 28 to 36 weeks gestation. RSVpreF vaccine is authorised in Canada at 32 to 36 weeks gestation. This off-label recommendation from NACI  is supported by safety and efficacy data, supports broader access and opportunities for immunization, and aligns with recommendations by the World Health Organization.
• Clesrovimab is not authorized for infants and children at ongoing risk in their second RSV season but could be considered for off-label use based on current evidence of immunogenicity and safety.
• Due to a lack of data at this time, NACI currently has no recommendations for repeat RSVpreF vaccine dosing during subsequent pregnancies. To provide protection to infants born in subsequent pregnancies, the use of monoclonal antibodies should be considered.
• Nirsevimab or clesrovimab could be administered on the same day, or at any time before or after, routine childhood vaccines. Concurrent administration of RSVpreF to pregnant women and pregnant people with other recommended vaccines can be considered according to basic vaccine principles.

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