Neonatal Drug Therapy Manual

Nirsevimab

Disclaimer: Official controlled document is the CHEO and Ottawa Hospital online copy. It is the responsibility of user to ensure that any paper copy version is the same as the online version before use.

Updated October 13, 2026 - 1:42pm

Alternate Name(s): 
Beyfortus
Classification: 
Human Monoclonal Antibody; passive immunizing agent
Original Date: 
September 2024
Revised Date: 
October 2026
Indications: 

The following information is recommendations for Ontario patients. For other provinces, double check their provincial guidelines

 

  1. Prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in eligible neonates and infants born April 1 2026 or after and less than 8 months of age up to the end of the RSV season:

a. All premature infants < 37 weeks gestation, regardless of maternal RSV vaccine (Abrysvo®) history

b. All infants deemed high risk (consult provincial guidelines), regardless of maternal RSV vaccine history ​

c. For term infants (> 37 weeks gestation) born April 1 2026 or after and less than 8 months of age up to the end of the RSV season and not high risk, nirsevimab   may be offered if:

  • The mother did not receive the RSV vaccine during pregnancy. 
  • The mother’s RSV vaccination status is unknown.
  • The infant was born within 14 days of mother's RSV vaccination

 

2. For their second RSV season, children less than 24 months of age who remain vulnerable to severe RSV disease, and following a discussion with their pediatrician or pediatric specialist (for example, health-care provider with a specialization in high-risk pediatrics), including children with:

  • chronic lung disease (CLD), including bronchopulmonary dysplasia
  • hemodynamically significant congenital heart disease (CHD)
  • severe immunodeficiency
  • Down Syndrome/Trisomy 21
  • cystic fibrosis with respiratory involvement and/or growth delay
  • neuromuscular disease and congenital airway abnormalities that impair the clearance of respiratory secretions
     

3. MOH Ontario allows immunization of Quebec or Nunavut infants when:​

  • Infants are born in an Ontario hospital during RSV season before discharge home ​

OR​

  • Children are being medically cared for in Ontario during RSV season (i.e., by a pediatric specialist or hospitalized) and meet one of the eligibility criteria in the Ontario guidance.​
Administration: 
  • IM
  • The 200 mg (2 mL) dose should be given as two separate 1 mL IM injections, in separate injection sites
Dosage: 

Dosing:

  • < 5kg: 50 mg (0.5 mL) IM once

  • > 5 kg: 100 mg (1 mL) IM once

Some infants will qualify for a second season, in which they will receive 200 mg (2 mL) IM once during that season

 

Timing (Ontario Guidelines. For other provinces, refer to their provincial guidelines):

  • Infants' First RSV season:
    • Infants born in 2024 prior to the RSV season should receive nirsevimab shortly before1 or during the RSV season 
    • If infants are born shortly before1 or during the RSV season should receive nirsevimab within the first week of birth2
  • For high risk infants who qualify for a second RSV season:
    • Should receive nirsevimab shortly before1 or during the RSV season 
Side Effects: 
  • Rash  
  • Fever 
  • Injection site reactions (redness, swelling, and pain) 
Reconstitution and Stability: 
  • Available as 50 mg and 100 mg pre-filled syringes
  • One time use
  • Refrigerate, protect from light. May be kept at room temperature (20℃ - 25℃) for a maximum of 8 hours. 
Compatibility: 
  • May be administered at same time as routine infant vaccines, though can be easier to monitor for side effects when given alone 
Notes: 

1nirsevimab has been shown to protect against severe RSV disease for at least 5 months, and the ideal timing of administration may differ depending on the clinical situation, timing of healthcare appointments, and local circulation of RSV. 

2Most infants born during the season will receive their immunization in the first week of life, however this can be delayed if critically unwell/admitted to intensive care. 

References: 
  • AstraZeneca Canada Inc. (2023). BEYFORTUS® Product Monograph. 
  • Ministry of Health. (2024). Respiratory Syncytial Virus (RSV) Prevention Program – Monoclonal antibody for infants and high-risk children. 
  • CDC-Frequently Asked Questions About RSV Immunization with Monoclonal Antibody for Children 19 Months and Younger, accessed Sept 2024. 

  • Respiratory syncytial virus (RSV) vaccines: Canadian Immunization Guide, accessed Sept 2024. 

The information contained on this website is provided for informational purposes only, as a guide to assist physicians, nurses and other healthcare providers in deciding on the appropriate care required for a particular patient. At all times, physicians, nurses and other healthcare providers must exercise their independent clinical judgment, based on their knowledge, training and experience, taking into account the specific facts and circumstances of each patient, when deciding on the appropriate course of investigation and/or treatment to recommend in a particular clinical situation.

CHEO has made every effort to ensure that the information contained on this website is as current and accurate as possible. However, changes can occur due to ongoing research and the constant influx of new information. Where possible, hospitals and healthcare practitioners should verify the information before acting on it.

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