Some Ontario doctors have started offering a free shot that can protect babies from respiratory syncytial virus while Quebec will begin its immunization program next month.

The new shot called Nirsevimab gives babies antibodies that provide passive immunity to RSV, a major cause of serious lower respiratory tract infections for infants and seniors, which can cause bronchiolitis or pneumonia.

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Ontario’s ministry of health says the shot is already available at some doctor’s offices in Ontario with the province’s remaining supply set to arrive by the end of the month.

Quebec will begin administering the shots on Nov. 4 to babies born in hospitals and delivery centers.

Parents in Quebec with babies under six months or those who are older but more vulnerable to infection can also book immunization appointments online.

The injection will be available in Nunavut and Yukon this fall and winter, though administration start dates have not yet been announced.

With files from The Canadian Press’ Nicole Ireland