Ontario is expanding its respiratory virus vaccination program this year for infants, high-risk children and pregnant women ahead of the fall flu season.

The government announced Thursday that it would be significantly expanding eligibility for respiratory syncytial virus (RSV) vaccines as it aims to protect at-risk children and mothers from the potentially serious virus.

Beginning in the fall, families with infants and high-risk children two years old or younger will be able to access a publicly funded RSV vaccine. Pregnant women will be eligible for a similar shot that can protect their child for six months after birth.

“To be ready for this year’s respiratory illness season, we all need to take the simple and effective steps to protect the most vulnerable people in our communities and our health care system,” Dr. Kieran Moore, Ontario’s chief medical officer of health, said in a statement.

“RSV is a highly contagious virus that causes infections of the respiratory tract, especially in the very young and older members of our communities.”

Moore said the expansion means all high-risk children aged 24 months and younger will be eligible for protection this coming fall.

Dr. Chris Simpson, the chief medical executive of Ontario Health, called the move a “game changer” to protect children.

Flu season has become more complex for the health-care system since the start of the COVID-19 pandemic, with a so-called triple threat of influenza, COVID-19 and RSV circulating. The colder months have seen a particular strain on children’s hospitals as a result of the three viruses.

“By expanding the number of children eligible under the RSV prevention program, our government is making it easier for families to access the care and protection they need ahead of respiratory illness season,” Health Minister Sylvia Jones said.