Should You Get Another COVID Vaccine?

It’s been about nine months since the Omicron variant arrived in the country and Canadians were lining up for COVID shot number three. We got boosted (or at least 56 percent of us over the age of 12 did), we were more diligent about wearing masks and social distancing, and the number of infections decreased right in time for summer. But now, provinces in Canada are reporting a new wave of infections, this time driven by Omicron’s highly contagious BA.4 and BA.5 subvariants. In response, provinces are offering fourth doses of the COVID vaccine to certain population groups. 

We spoke to Dr. Horacio Bach, a clinical assistant professor at the University of British Columbia’s division of infectious diseases, and Dr. Dawn Bowdish, a professor of medicine at McMaster University and the Canada Research Chair in Ageing and Immunity, to learn more.

Who is eligible for a fourth dose?

If you’re in the 44 percent of the population over the age of 12 who hasn’t gotten their booster (a.k.a. the third dose), experts advise doing so now. It’ll help keep you protected as the country goes through the new wave.

As for the fourth dose, eligibility varies from province to province. In Ontario, Quebec, Yukon, Nunavut, Alberta and New Brunswick, anyone over the age of 18 is eligible for their fourth dose. In PEI, anyone over the age of 12 is eligible. In British Columbia, Saskatchewan, Manitoba, Nova Scotia, Newfoundland and Labrador and the Northwest Territories, only people in vulnerable groups such as seniors, those with compromised immune systems and those living in group settings are eligible to receive their fourth dose. 

Did you recently receive your third dose? Some provinces require at least three months between your third and fourth dose, while other provinces require six. A recent COVID infection will also prevent you from getting another shot: Most provinces require that you be three months post-infection before rolling up your sleeves.

Why are some provinces allowing the general population to get fourth doses and some aren’t?

“There are two philosophies around who should get vaccinated and when,” says Bowdish. Public health agencies in some provinces believe only those who are at a high risk of getting seriously ill, such as older adults and immunocompromised people, need a fourth dose. Others believe vaccinating the general public can reduce the total amount of infections and prevent infections from reaching vulnerable communities. 

Are fourth doses effective, particularly against Omicron?

“The vaccine we are using is based on the first COVID-19 virus,” Bach says, “but, the virus has gone through several rounds of evolution.” So the vaccine isn’t as protective against the newer variant, Omicron, and its subvariants.

 A recent study from the CDC found that fourth doses were 80 percent effective against severe illness from Omicron. Although the newer BA.4 and BA.5 subvariants that are driving the current wave of cases in Canada weren’t part of this study, Bowdish says a fourth dose is indeed effective at reducing infections. But, there’s a catch: “It’s time limited,” she says. “You get only three months of really good protection and then it starts to wane.”

What if you’ve already had COVID—when should you consider a fourth dose?

Both Bach and Bowdish say it’s unclear exactly how long immunity from a COVID infection lasts, and BA.5 is good at dodging the immune system.

Bowdish recommends that people who’ve recently had COVID (within the last three months) wait to get their fourth dose. The antibodies their body produced to fight the virus when they were sick can help keep them protected until they get another dose, which would provide an additional three to six months of protection, she says. All provinces advise waiting about three months before getting their next dose.  

Are there any risks to getting another dose?

Bowdish and Bach agree there are no downsides to getting a fourth dose. “While there’s been some worry we’re boosting too much, that’s actually a misconception,” says Bowdish. “There’s no evidence in the history of vaccination of that ever happening.”

And, while earlier concerns around vaccine supply might’ve prompted people to worry about jumping the “vaccine line,” we’re no longer in a situation where the demand for vaccines is outpacing supply—there’s enough for everyone who wants one.

 What’s this I hear about the Omicron-specific vaccine? Is it worth waiting for?

mRNA vaccines, which are the type of COVID vaccine that most of us already have, can be tweaked to target the Omicron variant. Currently, Pfizer and Moderna are both testing retooled versions of their vaccines to include the Omicron variant and are on track to be ready by the fall. But it could be as late as December. 

Bowdish says instead of waiting, we should consider getting another dose three to six months after our last booster or infection.

What else should people consider when thinking about getting their fourth dose?

If there’s some big event or trip coming up, Bowdish recommends getting a vaccine two weeks before you leave. “That’s a pretty good insurance policy to ensure that your trip isn’t disrupted by being ill.”  

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