Seniors, long-term care residents, hospital staff and patients in Ontario will be able to get the flu shot starting this week.
Vaccination will open to everyone else in the province aged six months and older on Oct. 27.
Most other provinces and territories are expected to begin their flu shot programs in mid-October.
Dr. Netisha Gupta of the Lung Health Foundation says young children, seniors and people with asthma and chronic obstructive pulmonary disease — known as COPD — are at especially high risk of severe illness from the flu.
While the flu vaccine can reduce the risk of falling ill, she says it’s most effective at making infections that do occur milder and preventing hospitalization.
Gupta says it takes about two weeks for that protection to take hold after getting the shot.
The vaccine prevents severe outcomes by preparing the immune system to recognize and fight the virus when it appears, she said.
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“Your body already knows how to respond so you don’t have a severe reaction. So you don’t end up in the hospital. So you don’t end up, you know, having pneumonia,” Gupta said.
Dr. Jesse Papenburg, a pediatric infectious disease specialist and medical microbiologist at the Montreal Children’s Hospital, said the vaccine reduces the need for a visit to the doctor or hospitalization by about half.
Papenburg, who is also an associate professor of pediatrics at McGill University, was a co-lead author of a recent study that looked at people aged 16 and younger who were hospitalized or died from influenza in Canada between 2004 and 2022.
The study, published in the Journal of Pediatrics in July, found 80 children and youth died during that time period and 12,887 were hospitalized.
More than half of the children who died were under five years of age.
“We know that young age is a risk factor for more severe influenza disease, in part because they haven’t been exposed to as many infections with influenza, so they don’t have as much immunity,” said Papenburg.
“Also in part, especially in young babies, they’re more vulnerable because of the smaller size of their airways.”
About three-quarters of the kids who died had an underlying chronic medical condition, Papenburg said.
Only one in four patients in the study had been vaccinated.
“Fortunately, mortality due to influenza in children is infrequent. But on the flip side, it is also potentially preventable,” he said.
“One of the take-home messages of the study is that the flu is not just another benign cold-like illness, that it can have serious complications that can lead to hospitalization, but also can even lead to death.”
The study used data from the IMPACT surveillance network, which includes 12 Canadian pediatric hospitals.
© 2025 The Canadian Press
