Flu cases on the rise in Alberta, while immunization uptake remains low

Flu cases are on the rise across the province, while immunization uptake is the lowest it's been in more than a decade, two infectious disease experts say.

Provincial data shows Alberta has seen more than 3,000 recorded flu cases during the 2024-25 season, with more than 750 hospitalizations. As of Jan. 4, 25 people in the province have died from the flu.

Craig Jenne, a professor in the department of microbiology, immunology and infectious diseases at the University of Calgary, says cases are rising while Alberta is seeing the lowest influenza immunization rate in more than a decade and a half.

"Last year was actually a remarkably low immunization uptake, probably the lowest in about a dozen years... So far this year, we're still under 20 per cent," he said, adding the low uptake is partly why the province is seeing so many cases.

During the 2023-2024 flu season, vaccine uptake in the province was 25 per cent. It hit a 10-year high during the COVID-19 pandemic at 37 per cent, but waned in the years that followed.

"I am hearing first hand from people that are in the hospital system saying that a number of the units are still well over 100 per cent occupancy," Jenne said. 

"We really do need these numbers to start coming down. because we are having a difficult time."

Jenne adds it's not too late to get immunized against the flu. He says every season there are two or three different strains of the virus, and getting infected with one will not protect you against the others.

"The influenza vaccine we offer in the province actually contains four different flu strains," Jenne said. "So even getting a vaccination now, if you've had the flu earlier this year, may still protect you."

During last year's flu season, with low vaccine uptake, Alberta saw the highest number of influenza-caused deaths it had recorded in 15 years. With this year's immunization rates trending even lower, Jenne says he's concerned.

RSV and SARS-CoV-2 — the coronavirus that causes COVID-19 — are also putting strain on the province's hospitals. More than 500 people are currently hospitalized for influenza, RSV or SARS-CoV-2, as of Jan. 4, provincial data shows.

"We really do need to get those that are most at risk protected, so we can ease that burden on the health-care system," he said.

Lynora Saxinger, an infectious diseases specialist at the University of Alberta Hospital, says this year's flu season started roughly four or five weeks later than it has the last few years.

This season has been atypical, she adds, in that most of Alberta's recorded flu cases are either H1N1 or H3N2.

"That can actually make a difference, because H1N1 you tend to get more hospitalizations in younger age groups and H3N2 you tend to get more hospitalizations in the very young and the very old," Saxinger said. "This year, it's actually a split, which is really quite unusual."

With so many respiratory virus cases and hospitalizations this year, Saxinger encourages more people to get the flu shot to help relieve strain on the health-care system.

"In a bad flu year, 10 per cent of the population can get influenza, so there's a lot of people who can get sick... it still is something for people to consider," Saxinger said. 

It's still too early to tell if the province has hit its peak in respiratory virus cases this season. Even if it has, Saxinger says people shouldn't let their guards down as flu seasons can drag on longer than anticipated and influenza can often stick around in communities for weeks after the peak period.

She adds the number of hospitalizations province-wide may continue to trend upwards for a time before they come down.

"If you look at the shape of those curves, they go up, they come down, so there's usually about as many cases coming down as going up," she said.