Respiratory Syncytial Virus (RSV) is a common virus that can cause serious lung infections, especially in infants and young children. To protect against severe RSV infections, there is a medication, called nirsevimab (Beyfortus®) available for all babies during their first winter season, and in some cases, babies under two years of age.
Beyfortus® is a preventive medication given as a single injection that provides six months of protection during RSV season by blocking the virus. This antibody treatment, which is different from a vaccine, helps reduce the risk of hospitalization from severe RSV infection, offering safe and effective protection for infants.
What is RSV?
RSV is a common virus that can cause lung infections, especially in children. It usually presents like a cold, with mild symptoms in both children and adults. RSV spreads through droplets from a cough, sneeze, or from touching an infected surface. The virus can enter the body through the eyes, nose, or mouth. RSV can survive on different surfaces for a while, which makes it easy to spread.
Most children will have had RSV by two years of age. RSV is more common in the winter during cold and flu season but can start earlier or last longer in some places.
While most children have mild symptoms, young babies can get very sick with conditions like bronchiolitis or pneumonia. These serious infections can make it hard to breathe and may need hospital care.
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Bronchiolitis is an infection in the smallest airways of the lungs. When these airways swell and become inflamed, mucus can build up, making it hard to breathe. Most cases of bronchiolitis are caused by RSV.
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Pneumonia is a lung infection that can cause symptoms like coughing, fever, and difficulty breathing, ranging from mild to severe.
Signs and symptoms:
RSV symptoms are usually mild and go away in a few days, but can be more serious in babies and older adults, sometimes leading to lung infections and hospitalization.
- Coughing
- Runny nose
- Fever
- Wheezing
- Decreased appetite, ability to drink and reduced energy
- Irritability in young children
How to protect your infant
It is important to wash hands often, clean surfaces, stay home when sick, avoid smoking near your child, avoid large crowd events and avoid touching your face. Despite best efforts, it is nearly impossible to avoid babies being exposed to respiratory viruses, especially if they have older siblings.
There are two approved products in Ontario that can help protect infants from RSV:
- A preventive antibody medication for infants – nirsevimab (Beyfortus®)
- A vaccine for pregnant individuals – RSVpreF vaccine (Abrysvo®)
Only one option is necessary for protection unless advised otherwise by a health care professional. The best available medication to prevent RSV in young children is Beyfortus® because it provides better and longer-lasting protection for babies. Abrysvo in pregnancy should only be considered as an alternative if parents choose not to immunize their baby with Beyfortus after birth.
About Beyfortus
Beyfortus® (nirsevimab) is not a vaccine. It works by giving your baby ready-made antibodies that protect against RSV immediately, instead of making the immune system create antibodies to fight infection.
These antibodies help block the virus from infecting your baby’s body and provide protection for at least 6 months, covering the typical RSV season. Over time, the antibodies fade, but they offer strong protection during the most critical months when RSV is most common.
Monoclonal Antibodies (ready-made antibodies) are proteins that are developed to act like the antibodies your body produces.
Antibodies are proteins your body makes that help get rid of germs/harmful substances that enter your body, such as bacteria and viruses.
Beyfortus® protects your baby from RSV in their first RSV season. It may also be given during the second RSV season to children less than 2 years of age who are vulnerable to severe RSV disease. Contact your health care provider if you think your child may be eligible for Beyfortus® if your child is older than 12 months.
Eligibility/High-risk Eligibility
For the 2025-2026 RSV season, Babies born between January to April 2025 will not qualify unless identified as higher risk (for example, if a baby was born prematurely or if they have underlying medical conditions). Infants immunized in March or early April 2025 can receive repeat immunization in October 2025 at the start of the season at the healthcare provider’s discretion.
Children up to 24 months of age who remain vulnerable from severe RSV disease through their second RSV season, with:
- Chronic lung disease of prematurity (CLD), including bronchopulmonary dysplasia, requiring ongoing assisted ventilation, oxygen therapy or chronic medical therapy in the 6 months prior to the start of RSV season
- Note: Children who were < 12 months of age and approved for coverage in the previous RSV season for chronic lung disease and bronchopulmonary dysplasia remain eligible.
- Hemodynamically significant congenital heart disease (CHD) requiring corrective surgery or are on cardiac medication for congestive heart failure or diagnosed with moderate to severe pulmonary hypertension
- Severe immunodeficiency
- Down Syndrome / Trisomy 21
- Cystic fibrosis with respiratory involvement and/or growth delay
- Severe congenital airway anomalies impairing the clearing of respiratory secretions
Resources & community clinics
