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.
In 2023, one new preventive antibody medication, nirsevimab (Beyfortus) and two new RSV vaccines, RSVpreF (Abrysvo) and RSVPreF3 (Arexvy), were approved for use in Canada. Both vaccines (RSVpreF and RSVPreF3) are approved for adults over the age of 60, while RSVpreF is also approved for pregnant individuals.
How do RSV preventive antibody medications work?
Nirsevimab is not a vaccine. Like palivizumab, it is a preventive antibody and provides infants with protection from RSV, in a similar way that the body’s own antibodies provide protection against infections. Unlike palivizumab, nirsevimab is a long-acting preventive antibody and one dose provides protection that works best in the first 6 months after being given. Nirsevimab has been shown to reduce the rate of hospitalization of infants for RSV infections by over 80%. It also reduces 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. 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 can be administered to infants any time after birth (including immediately after birth before discharge home) and is recommended for:
- all infants younger than 8 months at the beginning of the RSV season and all infants born during the RSV season
- 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 can be given at the same time as other childhood vaccines. For young children that are eligible and who have not received nirsevimab 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 recommended in the third trimester of pregnancy. When administered to pregnant individuals between 32 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 over 50%. However, Canada’s National Advisory Committee on Immunization (NACI) recommends immunization of infants with a preventive antibody medication as the preferred form of protection against RSV infection over vaccination of a pregnant individual. This recommendation is based on how well preventive antibody medications work and how long they can provide protection.
RSVpreF (Abrysvo) and RSVPreF3 (Arexvy) are also both recommended for older adults:
- 75 years of age and older, particularly for those who are at increased risk of severe RSV disease based on pre-existing health conditions
- 60 years of age and older who are residents of nursing homes and other chronic care facilities.
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 is 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.
