When Will Canada Reach Herd Immunity?

More Canadians are getting their COVID-19 vaccines, at least their first doses, which means we’re slowly crawling our way out of the pandemic. As of April 27, about 12.5 million doses have been administered across Canada, and around 30% of Canadians have received at least one shot. Just under 3% are fully vaccinated — a sluggish rollout compared to our U.S. neighbours. Still, things are happening.

The federal government recently unveiled modelling that showed restrictive measures *could* be loosened when 75% of Canadians have received their first dose of the COVID-19 vaccine and 20% have both shots. That means, according to Canada’s top doc Dr. Theresa Tam, some restrictions may be lifted by this summer if we meet that target. 

But when will we actually achieve herd immunity against COVID-19 — the situation when enough people have immunity so that the chain of transmission is broken and we can resume some sense of normalcy — in Canada?

We could be in for a bit of a wait.

Experts have been citing a total vaccination rate of 60% to 70% since the start of the pandemic, but with variants of concerns dominating the third wave, that number may be higher because they spread more easily and escape some — but not all — of the immune response, Tania Watts, a professor of immunology at the University of Toronto, tells Refinery29.

“Some people are suggesting a total of 85% where new variants are spreading, so in places like New York City where 25% of the population seems to have antibodies, they may reach [herd immunity] when 60% are vaccinated,” says Watts. “But this remains to be determined empirically.”

While she says that a single vaccine dose offers some protection, both jabs are needed to keep things under as best control as possible: “If the hotspots are vaccinated quickly, we may see caseloads drop by mid-summer, but will need to follow up with second doses through the fall to maintain immunity as we open up again."

Cynthia Carr, an epidemiologist and founder of Winnipeg-based EPI Research Inc., tells Refinery29 that it’s important that the vaccine rollout encompasses all of Canada, and that herd immunity is reached across the country, not just in hotspots. Infection can continue to spread if there are pockets of the country that do not have the same high vaccination rate as others. “We might have 70% of people that are vaccinated overall, but if you have communities where nobody's vaccinated, then all you need is one person to become infected and you have an outbreak within that community,” Carr says. “Then, that outbreak now creates enough cases that it impacts the rest of us that are only at 70% herd immunity.”

Because variants of concern are spreading in Canada and more young people are getting sick, both Watts and Carr stress the importance of rolling up your sleeve as soon as you’re able to. Eligibility varies across the country (and it's up to provinces to make it available pending supplies), but the National Advisory Committee on Immunization now says the AstraZeneca vaccine can be administered to anyone over 30.

While it’s important to be informed about possible side effects, the risks from contracting COVID-19 are much higher than any vaccine, Watts says. COVID-19 vaccines have been shown to be safe and effective, and are a vital tool in achieving herd immunity. “We all need to do our part to take the first vaccine offered," she says. "They all protect from severe illness and ICU admission compared to no vaccine.”