Experts fear this year's flu season could be particularly severe, and are wondering if the vaccine might need to be redesigned in the face of new strains that make it less effective.
Every year, scientists look to Australia for a glimpse of what might be in store for North Americans come flu season. And this year the numbers aren't pretty.
In October, over 215,000 cases of the flu had been confirmed by Australian laboratories, far higher than the 59,000 diagnosed in Australia during the "swine flu" H1N1 pandemic in 2009, researchers wrote in an article published in the New England Journal of Medicine on Wednesday.
There are three types of flu: influenza A, B and C. Influenza A is the most dangerous and has lead to pandemics like "swine flu" or "bird flu," while B is usually much less serious, but can still be deadly. Type C is the least serious, and is usually not recorded by researchers.
This year's predominant strain of influenza A is H3N2, and researchers estimate that the vaccine will only protect 10 per cent of those who receive it. The vaccine prevents 40 to 60 per cent of cases on years when the strains are well matched, but that rate can be much lower for specific variants.
Scientists meet at the World Health Organization early every year to predict what strains will be most prominent, and then make and distribute those vaccines over a period of months based on those predictions — putting medicine a few steps behind the quickly-mutating influenza.
When there's a mismatch between the strains the vaccine was created to prevent and what strains actually spread, people get sick, which is what happened last year.
"This mismatch most likely contributed to the severity of the 2014–2015 influenza season and the substantial related morbidity and mortality among people over 65 years of age," wrote researchers in the the New England Journal of Medicine.
The researchers said the issues with the vaccine last year and this year show that it might be time to focus on creating a "universal" vaccine that would protect against seasonal variants of the illness and be more durable.
But they say it's still extremely important for people to get vaccinated, as herd immunity — when enough members of a community get vaccinated to prevent a dangerous outbreak — can protect vulnerable members of the community, like children, seniors and people with serious illnesses that impact their immune system.
Health Canada has reported increased levels of both influenza A and B this year with 2,080 confirmed cases as of late November, and noted that the levels of influenza B were as high as they usually are in mid-February.
As of Nov. 25, 371 people across Canada have been hospitalized due to the flu and eight have died.
Southern Alberta and southern Ontario have been the two hardest-hit regions so far.
Visit Health Canada's website to find out where you can get a flu shot in your province.
CLARIFICATION: An earlier version of this story did not clarify that the effectiveness of flu shots can vary from strain to strain and year to year.
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