information For healthcare providers
RSV Protection: Side Effects & Safety
Like all medicines and vaccines, RSV protection options can cause side effects. Not everyone will experience them, and most side effects are mild and get better on their own. Serious side effects are rare but can happen. This page provides a clinically relevant summary of adverse events, contraindications, and safety considerations associated with the two currently authorised RSV prevention options in Canada. This material presents a balanced overview of both benefits and risks associated with RSV prevention strategies, but it does not replace the full Product Monographs.
Healthcare professionals are encouraged to review the complete Product Monograph and NACI recommendations prior to prescribing, administering, or counselling patients.
Infant RSV Immunization
Therapeutic classification: Recombinant human monoclonal antibody
Health Canada Indication: Passive immunization for the prevention of RSV lower respiratory tract disease in neonates and infants.
Mechanism of action: Binds to the prefusion F protein of RSV, neutralising viral entry and preventing viral replication in the respiratory tract.
Adverse Reactions:
- Common adverse events (≥1/100 to <1/10):
- Injection site reactions: erythema, swelling, induration, pain
- Rash
- Pyrexia (fever)
- Less common adverse events (rare):
- Severe hypersensitivity reactions (including anaphylaxis) have been reported post-marketing.
- Anaphylaxis has been observed with human immunoglobulin G1 (IgG1) monoclonal antibodies.
Contraindications:
- Contraindicated in individuals with a history of severe hypersensitivity, including anaphylaxis, to nirsevimab or any component of the formulation.
Precautions:
- Use caution in infants with a history of severe allergic conditions.
- Emergency treatment for anaphylaxis must be immediately available.
- Immunization may not provide the same level of protection in individuals with protein-losing conditions
Special populations:
- Safety and efficacy data in preterm infants demonstrate protective benefits but warrant careful monitoring due to clinical vulnerability.
- Data in infants with severe immunocompromise or chronic respiratory disease are limited; risk-benefit should be assessed individually.
Healthcare providers should report suspected adverse reactions through the adverse events following immunization (AEFI) reporting form.
Maternal RSV Vaccine
Therapeutic classification: Bivalent pre-fusion F subunit vaccine
Health Canada Indication: Active immunization of pregnant individuals between 32 and 36 weeks’ gestation to prevent RSV-associated lower respiratory tract disease in infants from birth to 6 months of age.
Mechanism of action: Induces maternal RSV-neutralising antibodies that cross the placenta via FcRn-mediated transfer, conferring passive immunity to the newborn.
Adverse Reactions:
- Common adverse events (may affect more than 1 in 10 people)
- Pain where the injection is given
- Headache
- Muscle pain (myalgia)
- Less common adverse events (may affect up to 1 in 10 people)
- Redness and/or swelling where the injection is given
- Severe (rare)
- Hypersensitivity reactions
- Anaphylaxis
- Infants
- No side effects were reported in infants born to vaccinated mothers
Pregnancy-specific safety considerations:
- In phase III clinical trials, events such as the following were reported in both control and vaccinated groups:
- Preterm birth
- Gestational hypertension
- Pre-eclampsia
- Stillbirth
- A numerical imbalance in preterm birth was observed in one large trial; however, available evidence does not establish a causal relationship between the vaccine and these outcomes
- To mitigate potential risk, Health Canada has restricted use to 32–36 weeks’ gestation
Contraindications:
- History of severe allergic reaction to a previous RSVpreF dose
- Known hypersensitivity to any component of the vaccine
Precautions & Warnings:
- Defer vaccination in individuals with acute febrile illness
- Assess prior history of severe allergic reaction to vaccines or injectable biologics
- Pregnancy-specific risk assessment should include obstetric history, gestational age verification and concurrent medical conditions
Healthcare providers should report suspected adverse reactions through the adverse events following immunization (AEFI) reporting form.