Everything You Need To Know About The New COVID-19 Vaccine

It’s not about how many shots you’ve had—it’s about how recent they are.
A female doctor administers a COVID-19 vaccine to a woman (Photo: iStock)

This fall, medical experts say Canadians ages five and up should receive an updated COVID-19 vaccine dose—even if they’ve previously been vaccinated.

Public health authorities, who examine key indicators of spread like wastewater, test positivity rates and hospitalization numbers, say that COVID levels are expected to continue rising through the next few weeks. It’s likely been a while since most people have had a vaccine or infection, and the emergence of new variants makes getting the new vaccines necessary for protection.

Vaccines help protect against serious and lasting illness at the individual level, and can also reduce infection levels in the community. But there’s been a lot of confusion surrounding this fall’s updated COVID-19 shots. To help navigate vaccine decisions in the coming weeks, we asked two immunology experts to weigh in.

How do this fall’s COVID-19 vaccines differ from previous iterations?

Last year’s bivalent formulas targeted both the original strain of COVID-19 and variants that were circulating at the time. Now, the original strain of COVID is practically extinct, so “there’s really no point vaccinating against that,” says Dawn Bowdish, an associate professor of medicine at McMaster University and a Canada Research Chair in Aging and Immunity.

That’s why this fall’s mRNA vaccines from Moderna and Pfizer are monovalent, targeting only the Omicron XBB.1.5 subvariant that emerged in fall 2022. The current dominant strain of COVID-19 in Canada is a descendant of XBB.1.5 called EG.5, so initial testing indicates that these updated monovalent shots will be effective for the fall, says Anna Blakney, assistant professor of bioengineering at the University of British Columbia and an RNA vaccine expert. Novavax, a vaccine manufacturer whose shot was approved for use in Canada in 2022, has also revised its protein-based formulation to target XBB variants.

While formulas have been revised, side effects—such as fatigue, headaches, dizziness and nausea—are expected to be similar to previous shots.


Health Canada is still evaluating the Novavax formulations, but it has approved Moderna and Pfizer’s updated vaccines as of September 28.

Who should get an updated COVID-19 vaccine dose this fall?

If at least six months have passed since your last COVID-19 infection or vaccine dose, Health Canada recommends that you receive a dose this fall. That includes people who are pregnant and elderly, as well as anyone who is currently experiencing long COVID. In fact, Bowdish says that some people with long COVID may see their symptoms improve after a vaccine, while a second infection can worsen them.

Blakney says that each vaccine formulation comes with specific guidelines. If you have children between six months to four years old who haven’t previously been vaccinated, they’re eligible for a primary series of two doses of those new variant-specific shots, while children in that age group who have been vaccinated once can receive one additional dose.

Why should I get vaccinated against COVID-19 this fall?

Blakney encourages people to weigh the risks of getting vaccinated against the benefits. “For any of the approved COVID vaccines, the benefit greatly outweighs their risk,” she says. COVID continues to hospitalize young children, the immunocompromised and the elderly, but even if you’re young and healthy, the virus can sometimes result in long-term health issues.

Bowdish adds that while COVID vaccines do not eliminate the risk of acquiring long COVID, there is evidence that they reduce the odds of being left with it after an infection, although we don’t know for sure by how much. Bowdish also says people should be aware that a COVID infection offers only temporary immunity, with an even shorter period of protection in the Omicron era. Plus, illness severity can vary unpredictably from infection to infection.


Even if you’re willing to take your chances with COVID, getting vaccinated can help protect your loved ones and your community. When you’re less likely to fall ill with COVID, you’re also less likely to infect others. Blakney says it’s worth thinking about the vulnerable people in your life who you can protect, like elderly folks and cancer patients. Bowdish adds that if more people get vaccinated, we’ll see fewer disruptions from work and in schools. “The more people are vaccinated, the less transmission we have in general,” she says.

When can I get the updated COVID-19 vaccine?

Each province and territory administers its own vaccination program, so Health Canada says vaccination timing may differ by region. Generally, provinces starting receiving deliveries of the updated Moderna shot beginning in late September and October. Not all provinces have released fall vaccination plans yet, but B.C. and Ontario will begin rollout with high-risk populations, opening eligibility to the general public as more doses become available.

For information about local vaccine appointment availability, Health Canada says people can contact their local public health unit.

It’s worth booking a vaccine appointment as soon as you’re eligible. Bowdish says that, since COVID is mutating quickly, vaccines are most effective at the beginning of a wave. Blakney adds that, for the sake of convenience, you can plan to get your COVID and flu vaccines at the same time—extensive research indicates that it’s safe and effective to do so.

How often will I need to get a COVID-19 vaccine in the future?

Bowdish and Blakney both agree that it’s not yet clear what the frequency of shots will be in the future. Blakney says that researchers and clinicians are beginning to think about the COVID vaccine as a seasonal shot rather than a booster. That’s because the word “booster” typically refers to follow-up shots that are protective over a long period of time, whereas with COVID, vaccines are only protective from symptomatic infection for about three to six months.


“We’re changing the terminology to reflect the fact that we will need continuously updated vaccines to deal with whatever variants are circulating, just like we do for influenza,” Bowdish says. The difference is that flu season lasts only about six months—the same amount of time that flu vaccines are protective. In contrast, COVID currently appears to cause multiple waves of infection each year.

“I've probably had 20-plus flu shots in my life, and if all goes well, I hope to have 40 more,” Bowdish says. “COVID is going to be the same thing, unless there’s a major change in the technology.”

“It’s not the number of vaccines that matters,” she adds. “It’s how recently you’ve had one.”


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