Why is RSV prevention important?
Respiratory syncytial virus (RSV) is a virus that can cause outbreaks and severe respiratory infections, including bronchiolitis and pneumonia in young infants, and in premature and young term infants, babies with heart, lung, airway or neurologic problems and in the elderly. While many healthy children and adults develop mild symptoms, those in high-risk categories have a higher likelihood of developing severe illness and being hospitalized. In the past, the only available immunization (palivizumab) was given to high-risk premature babies and babies with heart and lung conditions. Several RSV vaccines and immunizations are now approved for different age groups.
What RSV vaccines and immunizations are available?
For over 20 years, a monoclonal antibody, or preventive antibody medication called palivizumab was used to protect high-risk groups from RSV and in particular from developing severe RSV infections. It was provided to premature infants and infants with heart or lung problems every month from about November to April in the first two years of life. As a preventive antibody, palivizumab provided short-term (or passive) immunity to RSV. While this immunization protected babies at risk for severe infections due to RSV, there was no effective way to protect heathy infants or the elderly.
Starting in 2023, several newer RSV immunizations have been approved in Canada. Nirsevimab (Beyfortus) and clesrovimab (Enflonsia) are preventive antibodies approved for infants in their first RSV season. They are recommended for all infants up to 8 months of age. Nirsevimab is also recommended for children under age 2 who are at increased risk of severe disease. Several RSV vaccines, RSVpreF (Abrysvo), RSVPreF3 (Arexvy) and mRNA1345 (mRESVIA) are approved and recommended for older adults. RSVpreF is also approved for use in pregnancy.
How do RSV preventive antibody medications work?
Nirsevimab and clesrovimab are not vaccines. Like palivizumab, they are preventive antibodies and provide infants with protection from RSV, in a similar way that the body’s own antibodies provide protection against infections. Unlike palivizumab, nirsevimab and clesrovimab are long-acting preventive antibodies and one dose provides protection that works best in the first 6 months after being given. Both immunizations have been shown to reduce the rate of hospitalization of infants for RSV infections by over 80%. They also reduce the rate of infants requiring medical care for RSV.
How do RSV vaccines work?
RSVpreF (Abrysvo) and RSVPreF3 (Arexvy) are both recombinant non-live vaccines. MRNA1345 (mRESVIA) is an mRNA vaccine. They work by activating the immune system to produce antibodies that target RSV. One dose given as an injection into the arm provides long-lasting protection and does not need to be repeated every season.
Who can be immunized with an RSV preventive antibody medication?
Nirsevimab and clesrovimab can be administered to infants any time after birth (including immediately after birth before discharge home) and are recommended for all infants younger than 8 months at the beginning of the RSV season and all infants born during the RSV season.
Nirsevimab is also recommended for children with conditions that place them at risk for severe disease (for example: prematurity, congenital heart disease, chronic lung problems, immunodeficiency, airway problems and neuromuscular conditions) for their second RSV season.
Nirsevimab and clesrovimab can be given at the same time as other childhood vaccines. For young children that are eligible and who have not received nirsevimab or clesrovimab after birth, it can be given at their health-care provider’s office, as well as through certain outpatient hospital clinics.
Who can be immunized with an RSV vaccine?
RSVpreF (Abrysvo) is approved for use in the third trimester of pregnancy. In Canada, it is authorized for use between 32 and 36 weeks of pregnancy. Research has shown that when it is administered to pregnant individuals between 28 and 36 weeks of pregnancy, the antibodies that are produced will cross the placenta and provide protection to newborns from birth to 6 months of age. It is estimated that hospitalization rates of infants due to RSV can be reduced by 70% to 80%.
RSVPreF3 (Arexvy) and mRNA1345 (mRESVIA) are also approved for adults:
- 60 years of age and older
- 18 to 59 years of age who are at risk of severe disease
RSVpreF (ABrysvo) is approved for adults 50 years of age and older.
What are the current Canadian recommendations for adult RSV protection?
Current Canadian recommendations for adult RSV protection include:
- all adults 75 years of age and older
- adults 65 to 74 years of age who are at increased risk of severe RSV disease based on pre-existing health conditions
- adults 18 years of age and older who are residents of a nursing home or chronic care facility, have had a lung or stem cell transplant, are on dialysis or require chronic oxygen therapy
What are the current Canadian recommendations for infant RSV protection?
Current Canadian recommendations for infant RSV protection include:
- RSVpreF (Abrysvo) administered to pregnant individuals between 28 and 36 weeks of pregnancy OR
- Nirsevimab or clesrovimab administered to infants. This includes infants born to pregnant individuals who did not receive RSV vaccination at all or did not receive it more than 2 weeks prior to birth.
- High-risk infants should receive a dose of nirsevimab or clesrovimab even if RSV vaccination was provided during pregnancy. High-risk conditions include:
- prematurity less than 32 weeks
- chronic lung or airway conditions
- congenital heart disease affecting heart function
- immunodeficiency
- neuromuscular conditions
- Down syndrome
- cystic fibrosis
Are the RSV immunizations safe?
All the products approved in Canada for protection against RSV have been shown to be safe. Side effects are generally mild and are similar to the common side effects of other childhood vaccinations. They include:
- pain
- redness, lump or swelling at the injection site
Is RSV immunization free?
The 2024-25 RSV season was the first during which RSV vaccines and monoclonal antibodies became available in Canada. However, eligibility for immunization provided for free by the provinces currently varies by jurisdiction. Some provinces may first target specific populations. The development of free provincial RSV immunization programs across Canada will change over time. Extended health insurance plans may pay for a portion of the cost in provinces without a free RSV immunization program.