Coronavirus vaccines: What you should know about the side effects

Click to play video: 'Coronavirus: Anand says she has ‘full confidence’ in Health Canada’s COVID-19 vaccine approval process'
Coronavirus: Anand says she has ‘full confidence’ in Health Canada’s COVID-19 vaccine approval process
Coronavirus: Anand says she has ‘full confidence’ in Health Canada’s COVID-19 vaccine approval process – Dec 14, 2020

Almost a year into the coronavirus outbreak, and following months of scientific research and clinical trials by Pfizer and BioNTech, a newly approved COVID-19 vaccine began to roll out in Canada and the United States on Monday.

Understandably, there is renewed hope of much-needed protection against the coronavirus, but people are also concerned about the possible side effects.

“It’s really important to say that as we monitor the vaccines, adverse event reports will come up,” said Dr. Supriya Sharma, chief medical advisor with the regulatory branch of Health Canada, during a press conference announcing the agency’s approval of the Pfizer vaccine last week.

“But it is still a drug, still a vaccine, and there are potential risks even if they are rare.”

Story continues below advertisement

To address any concerns, the federal government is developing a new support program for Canadians experiencing a vaccine injury.

It is common for a vaccine or drug to have side effects. So, what do we know about the risks?


The most common side effects of the Pfizer vaccine that were reported in Phase 3 of the clinical trials were mild to moderate pain at the injection site, fatigue and headache.

These reactions were less common and milder in older people than younger adults, company data showed.

Vaccine recipients also got a fever. No COVID-19 related deaths were reported.

Click to play video: 'Ontario administers 1st COVID-19 vaccination'
Ontario administers 1st COVID-19 vaccination

Sharma said in the clinical trials, out of nearly 44,000 people, there were two cases of severe allergic reactions — one from the group that received the vaccine and the other that got the placebo.

Story continues below advertisement

“So it wasn’t a significant finding in the trials. However, we know that with all vaccines there’s a risk of allergic reactions.”

U.K’s medicine regulator has advised that people who have a history of significant allergic reactions to a vaccine, medicine or food should not receive the Pfizer vaccine.

The latest health and medical news emailed to you every Sunday.

This came after two NHS healthcare workers reported adverse effects on the first day of rollout.

According to Health Canada’s current guidelines, people who have had previous allergic reactions to any of the listed ingredients in the Pfizer vaccine should not get the vaccine.

Dr. Karina Top, an investigator at the Canadian Center for Vaccinology and professor at Dalhousie University, said an allergic reaction to any vaccine can start within minutes, but occasionally takes up to two to three hours after vaccination.

“Allergic reactions that develop more than four hours after vaccination are almost always due to another cause such as a reaction to a food or medication,” she told Global News.

Click to play video: 'Coronavirus: Health Canada says people allergic to any Pfizer vaccine ingredient should avoid use'
Coronavirus: Health Canada says people allergic to any Pfizer vaccine ingredient should avoid use


Moderna’s vaccine has not been approved anywhere in the world yet. The company has submitted its data from the clinical trials to Health Canada and it is under a rolling review process.

Story continues below advertisement

Like Pfizer, Moderna’s candidate was also manufactured using mRNA technology, a new way to make vaccines without using weakened or dead pieces of a virus.

During its late-stage clinical trials, pain at the place of injection was also reported after the first dose was given.

Following the second jab given four weeks later, participants experienced fatigue, muscle aches and pains, joint pain, headache and redness at the injection site.

The majority of adverse events were generally short-lived and were mild or moderate in severity, according to the U.S. drugmaker.

Top said participants in COVID-19 vaccine trials are being monitored for up to one to two years for the development of later symptoms that could be related to vaccination.

What about other non-COVID-19 vaccines?

The most common after-effect for all vaccines, including the flu shot, is a sore arm, experts say.

“About three to 10 per cent of the population may have other common after-effects such as fatigue (more frequent event) and less-common symptoms: fever of different levels, swelling, chills, vomiting, diarrhea and joint pain,” Levon Abrahamyan, a virologist at the University of Montreal, told Global News.

Story continues below advertisement

Most of these occur shortly after the vaccination or up to 24 hours later and then resolve within a day or two, Top explained.

“Some very rare adverse events that have been associated with vaccines in time but not necessarily proven to be caused by the vaccine, such as a neurologic condition called Guillain-Barre Syndrome, can occur a few weeks after the vaccination.”

Sponsored content