<< Seasonal Immunization

RSV (Respiratory Syncytial Virus) What You Should Know

What is RSV?

Respiratory Syncytial Virus (RSV) is a common respiratory virus that can cause mild cold-like symptoms, but in some cases, especially in infants and young children, it may lead to serious respiratory illness, including:

  • Bronchiolitis: swelling and inflammation in the small airways of the lungs.

  • Pneumonia: infection of the lungs.

  • Hospitalization and, rarely, death.

RSV is the most common cause of bronchiolitis and pneumonia among infants and young children.

RSV disease can have serious complications for infants, including hospitalization and intensive care unit admission, as well as significant impact on their caregivers and families.

Almost all children will have an RSV infection by the time they turn two. While most cases are mild, it is not possible to predict which infants will become seriously ill.¹

Who is at Risk?

Infants and young children are at the greatest risk of severe RSV illness, especially:

  • Babies younger than 6 months.

  • Infants born prematurely.

  • Children with lung or heart disease, or weakened immune systems.

  • Babies exposed to second-hand smoke.

  • Children who attend daycare or have school-aged siblings who may bring viruses home.²

Older adults, especially those living in long-term care facilities or with chronic illnesses, are also at increased risk of severe RSV disease.³

Symptoms of RSV

Most people experience mild, cold-like symptoms such as:

  • Runny nose

  • Cough

  • Sneezing

  • Fever

  • Decreased appetite

  • Wheezing or difficulty breathing (in more severe cases)

Seek medical attention immediately if your baby has:

  • Rapid or difficult breathing

  • Blue lips or fingernails

  • Difficulty feeding

  • Signs of dehydration

  • Unusual tiredness or difficulty waking

How Can I Protect My Child?

1. Immunization for RSV Prevention

Preventive immunization is available in Canada to help protect babies and young children during their first RSV season. This protection helps prevent severe illness and hospitalization. Ask your healthcare provider about what options are recommended for your child. Immunization is timed to provide protection during the RSV season.⁴

Infants and Children
Some babies and young children are at higher risk of severe illness from RSV, especially those born prematurely, those with certain health conditions, or those living in communities with limited access to care. To protect them, a preventive antibody treatment can be given before or during the RSV season. This reduces the chance of serious infection, hospitalization, and complications. The timing depends on the local RSV season, and in some cases, doses may need to be repeated throughout the season.

Pregnant Women
Pregnant women may also be offered an RSV vaccine in the late stages of pregnancy (around 32–36 weeks). This allows protective antibodies to pass to the baby before birth, helping shield the infant during their first months of life when they are most vulnerable. It needs to be given at least two weeks before delivery to give enough time for the protection to transfer.

2. Everyday Prevention Steps

  • Avoid close contact between your baby and people who are sick.

  • Wash your hands frequently and ensure others do too.

  • Keep your home, surfaces, and toys clean.

  • Avoid exposure to second-hand smoke.

  • Limit visitors and crowded places, especially during RSV season.

Who Should Consider RSV Immunization?

According to the Canadian Immunization Guide, the following groups may benefit from immunization or preventive treatment:⁴

  • All infants during their first RSV season.

    • First RSV season (birth to ~6 months of age):
      Babies born just before or during RSV season should receive protection soon after birth, ideally before they leave the hospital or shortly after going home. This timing helps shield them right away, since young infants are at the greatest risk of severe RSV.

    • Second RSV season (children under 2 years old):
      Children who are still medically fragile — such as those born very prematurely or with ongoing health conditions — may need another dose of protection going into their second season. This helps reduce their risk as their immune system continues to develop.

  • Infants born prematurely, or those with underlying medical conditions that place them at higher risk for severe RSV illness.

  • Infants of pregnant individuals immunized during late pregnancy.

  • Older adults living in long-term care or with chronic health conditions.

When is RSV Season?

In Canada, RSV activity is typically highest from late fall to early spring (November to April). Immunization or preventive treatment should be administered shortly before the start of RSV season.⁴

Are There Any Side Effects?

RSV immunization options are generally safe. Possible side effects may include:

  • Mild fever

  • Rash

  • Injection site reactions (redness, swelling)

  • Rarely, allergic reactions⁴

Your healthcare provider will explain the risks and benefits and help you decide what’s best for your child.

Talk to Your Doctor

Your healthcare provider can help determine whether RSV immunization is recommended for your child based on their age, medical history, and timing of the RSV season. Immunization is an important step to protect your baby's lungs during their most vulnerable stage.

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