Increased transmission of respiratory viruses upon return to school

After several back-to-school periods spent on guard due to COVID-19, it’s important to remember that other respiratory viruses are also circulating as cold temperatures set in and students find themselves in close proximity in the classroom. Vaccination is an effective way to protect against influenza, but vaccination rates are declining in Canada.

During the 2024-2025 flu season, one-third of adults received a flu shot, which is lower than in previous seasons. The same trend is observed among children, with 31 per cent of youth aged six months to 17 years receiving a flu shot for the 2023-2024 season, compared to 34 per cent the previous season.

Dr. Jesse Papenburg, a pediatrician, infectious disease specialist, and microbiologist at the Montreal Children’s Hospital of the McGill University Health Centre, confirms that some studies show a decline in vaccination rates among both adults and young children.

“We know that for various respiratory viruses, including influenza and respiratory syncytial virus, which is a major cause of hospitalization in toddlers under one year of age, these viruses circulate more during the winter in our climate, due in part to environmental factors,” explains Dr. Papenburg. “We’re talking about humidity, temperature, the amount of ultraviolet rays, so the amount of sunlight we get. These things change with the seasons and promote the circulation of these respiratory viruses during the winter.”

Dr. Papenburg points out that human behavior also plays a role.

“Human contact takes place much more indoors in enclosed spaces, such as daycares, schools, at the office for adults, and at home, indoors. This is also why we ask families when they have a child with a fever and cough, to keep them home so that they don’t spread the chain of transmission at school or daycare,” the pediatrician reminds.

More than 25,500 hospitalizations last year

The influenza vaccination campaign doesn’t begin at the start of the school year, but it doesn’t take too long to launch so that as many people as possible are protected before the onset of winter. Generally, the peak of the flu season occurs between November and March. Some years may experience a late or early peak, such as 2022-2023, when there were a very high number of transmissions from the beginning of November.

Most Canadian provinces will begin their influenza vaccination campaigns around October. Last year, Quebec launched its campaign in mid-October.

Flu vaccination is free in Canada for everyone aged six months and older.

People with chronic illnesses, underlying conditions (heart, respiratory, kidney, etc.), are at higher risk of influenza-related complications. The extremes of age, namely toddlers aged five and under and seniors aged 65 and over, are also more likely to develop complications that can lead to hospitalization or even death.

Last year, Health Canada recorded more than 25,500 hospitalizations and 689 deaths associated with the flu. Among children alone, more than 1,100 pediatric hospitalizations associated with the flu were reported. “This figure is an underestimate of the total number of pediatric hospitalizations,” Dr. Papenburg clarifies, “because many children are hospitalized in community hospitals.”

“It’s clear that the fewer people who get vaccinated, the greater the risk of flu-related hospitalizations, because we know that the vaccine is an effective way to prevent hospitalizations,” the pediatrician emphasizes.

He indicates that an individual who gets vaccinated will reduce their risk of seeing a doctor, going to the emergency room, or being hospitalized by about half.

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The Canadian Press’s health coverage is supported by a partnership with the Canadian Medical Association. The Canadian Press is solely responsible for this journalistic content.

–This report by La Presse Canadienne was translated by CityNews