Skip to main content
Complete Olympic Games coverage at your fingertips
Your inside track on the Olympic Games
Enjoy unlimited digital access
$1.99
per week for 24 weeks
Complete Olympic Games coverage at your fingertips
Your inside track onthe Olympics Games
$1.99
per week
for 24 weeks
// //

People line up outside an immunization clinic to get their Oxford-AstraZeneca COVID-19 vaccine in Edmonton on April 20, 2021.

JASON FRANSON/The Canadian Press

Candice Arnold says she’s never felt so happy about feeling so terrible. This week, as soon as people 40 and older became eligible for the AstraZeneca COVID-19 vaccine, the Winnipeg resident quickly booked an appointment and received her first dose.

About eight hours later, the side effects started. She felt tired and achy, as though she’d had a tough workout. Another two hours later, she woke up feeling like her head was in a vise. She was feverish, both chilly and hot, and lay in bed whimpering. The effects lasted about 20 hours, then she felt back to her old self.

It was worth it, Ms. Arnold says, saying she felt reassured the vaccine was working to produce an immune response. But not all her friends experienced that.

Story continues below advertisement

The riskiest thing about my AstraZeneca vaccination was the ride there

Getting the jab done: When can Canadians expect to get a COVID-19 vaccine?

“Some of them had the exact same reaction,” she says. “Others were like, ‘Oh, my arm’s a little sore.’ ”

Why do some people have what’s been described as a “vaccine hangover,” while others feel none at all? We asked experts to weigh in.

Why do some people have worse side-effects?

Younger people tend to have worse side effects than older adults, since our immune responses become less robust with age, says Jason Kindrachuk, assistant professor in the department of medical microbiology and infectious diseases at the University of Manitoba.

Women also seem to have more side effects than men. However, Dr. Kindrachuk says there’s not a clear answer yet as to why. Some researchers are examining how different sex hormones may play a role in differential immune responses between men and women, he says, while others are studying potential behavioural differences.

The important thing to note is that the vaccine’s effectiveness isn’t tied to how strong your reaction is, says Kelly Grindrod, a pharmacist and associate professor at the University of Waterloo School of Pharmacy.

“You don’t need to have side effects for the vaccine to work,” she says, saying all four approved vaccines – Pfizer, Moderna, AstraZeneca (and its counterpart Covishield) and Johnson & Johnson – work well, regardless of age.

Story continues below advertisement

How do the common side effects from the AstraZeneca (and Covishield) vaccine compare with those from mRNA vaccines by Pfizer and Moderna?

They’re quite similar, Dr. Grindrod says. Lately, people may be hearing more about side effects from the AstraZeneca vaccines because more younger people are getting them, now that they’re eligible, she says. Older people who received other vaccines are less likely to experience side effects in general, and front-line workers who were vaccinated during an earlier stage of the rollout are fewer in number, and perhaps less likely to share their experiences on social media, she says.

With AstraZeneca, about one-third of people have fever, two-thirds get fatigue, about a third experience joint pain, a little less than two-thirds get headaches and about a quarter have nausea, Dr. Grindrod said, saying this is about the same as for the mRNA vaccines. With the latter, however, the side effects tend to be worse after the second dose, whereas with AstraZeneca, they appear to be worse after the first dose, she says.

Bottom line: Don’t hold off for a different vaccine. Differences in how people respond have more to do with individual genetic differences than differences in vaccines, says Jorg Fritz, associate professor in the department of microbiology and immunology at McGill University.

Is it safe to take over-the-counter medications to alleviate discomfort?

“Absolutely,” Dr. Grindrod says, saying that even during vaccine trials, participants had the option of taking pain relievers, such as acetaminophen or ibuprofen. However, she says, she does not recommend using these medications pro-actively. “Don’t take it to avoid side effects.”

Story continues below advertisement

What should people expect when it comes to their second dose?

Because people’s immune response depends on individual genetic differences, it’s hard to say whether side effects will be more or less severe after the second dose, Dr. Fritz says. But, he says, the common side effects don’t last more than a day or two.

For her part, Ms. Arnold says she’ll be prepared when it comes time to get her second dose. She plans to have Tylenol and water at her side, and will not schedule anything for the next day, so she can ride out any discomfort.

“I’m not going to lie, I’m a little scared,” she says. “I’m very eager to get it, though, because I want to continue with life.”

Dr. Theresa Tam, Canada's chief public health officer, has explained why the National Advisory Committee on Immunization abruptly cancelled an expected announcement on Tuesday about its updated recommendations for the Oxford-AstraZeneca vaccine. Tam says the committee received some new data about the impact of COVID-19 variants of concern, and not because of any new information about the risk of blood clots that may be linked to the vaccine. The Canadian Press

Our Morning Update and Evening Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.

Your Globe

Build your personal news feed

  1. Follow topics and authors relevant to your reading interests.
  2. Check your Following feed daily, and never miss an article. Access your Following feed from your account menu at the top right corner of every page.

Follow the author of this article:

Follow topics related to this article:

View more suggestions in Following Read more about following topics and authors
Report an error Editorial code of conduct
Due to technical reasons, we have temporarily removed commenting from our articles. We hope to have this fixed soon. Thank you for your patience. If you are looking to give feedback on our new site, please send it along to feedback@globeandmail.com. If you want to write a letter to the editor, please forward to letters@globeandmail.com.

Welcome to The Globe and Mail’s comment community. This is a space where subscribers can engage with each other and Globe staff. Non-subscribers can read and sort comments but will not be able to engage with them in any way. Click here to subscribe.

If you would like to write a letter to the editor, please forward it to letters@globeandmail.com. Readers can also interact with The Globe on Facebook and Twitter .

Welcome to The Globe and Mail’s comment community. This is a space where subscribers can engage with each other and Globe staff. Non-subscribers can read and sort comments but will not be able to engage with them in any way. Click here to subscribe.

If you would like to write a letter to the editor, please forward it to letters@globeandmail.com. Readers can also interact with The Globe on Facebook and Twitter .

Welcome to The Globe and Mail’s comment community. This is a space where subscribers can engage with each other and Globe staff.

We aim to create a safe and valuable space for discussion and debate. That means:

  • Treat others as you wish to be treated
  • Criticize ideas, not people
  • Stay on topic
  • Avoid the use of toxic and offensive language
  • Flag bad behaviour

If you do not see your comment posted immediately, it is being reviewed by the moderation team and may appear shortly, generally within an hour.

We aim to have all comments reviewed in a timely manner.

Comments that violate our community guidelines will not be posted.

UPDATED: Read our community guidelines here

Discussion loading ...

To view this site properly, enable cookies in your browser. Read our privacy policy to learn more.
How to enable cookies