Why all COVID-19 vaccine side effects matter, not just the serious ones

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One of the leaders of the largest independent vaccine safety study in Canadian history says tracking the mild side effects of COVID-19 vaccines is as important as recording the rare serious ones.

“That’s really important to be able to put (side effects) in context and say: ‘How does what we’re seeing differ from what we’d be seeing in the population anyway on that given week?’” Dr. Jim Kellner told Global News.

The Calgary pediatric infectious diseases specialist is a co-investigator in the Canadian National Vaccine Safety Network’s (CANVAS) COVID-19 vaccine study.

While the Government of Canada’s system records the rare serious adverse events reported by health care professionals, the CANVAS study is asking Canadians to report their own symptoms after each dose by completing a questionnaire.

The researchers are also hoping people who have not yet had a COVID-19 vaccine will participate for comparison.

“One of the amazing things when it comes to looking at clinical trial results is how many people have what we call ‘side effects’ on any given day,” said Kellner.

“Things like fever, headache, not feeling well, sore muscles, sore joints — all these kinds of things happen to people even if they haven’t received an intervention such as a vaccine.”

Kellner says the study won’t necessarily rule out specific symptoms as side effects of a vaccine, but it could help track which reactions are more likely to affect certain populations. Plus self-reporting could turn up rare events not mentioned to doctors.

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“Somebody may have an adverse event, but if they don’t come forward (to a health care provider) and say that they’ve had that event, then it may go unmeasured.”

Among the nearly six million COVID-19 vaccine doses administered so far in Canada, 3,089 adverse events have been reported; 421 were considered serious.

That includes one case of a blood clot related to the AstraZeneca vaccine.

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Kellner says discovering such a rare side effect requires administering millions of doses. The more shots given beyond clinical trials, the more types of reactions will be detected.

He hopes the study can help reduce vaccine hesitancy, noting any reactions happen within the first eight weeks after a shot.

“Side effects of vaccines don’t come up for the first time months or years later.”

The researchers need to survey at least 300,000 people for each type of COVID-19 vaccine available in Canada, as well as a control group of Canadians who have not had a shot.

Volunteers can register online and fill out a survey eight days after receiving their first dose. A second survey takes place eight days after the second dose, then a final survey will be sent out six months after that.

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