Despite a growing push to roll out COVID-19 vaccine boosters more widely in Canada, epidemiologists say there is currently no evidence of an urgent need for additional shots in the general population — due to the strong, ongoing protection two doses already provide.
But with the emergence of the potentially more infectious omicron variant, the holidays rapidly approaching and COVID-19 levels remaining elevated in much of the country, should Canada wait for more proof of waning immunity before expanding eligibility of boosters?
Or should we move quickly to offer up additional shots to fend off another potential surge as the U.S., the U.K. and Israel have done?
Some provinces and territories have already expanded access to boosters — including Manitoba, the Northwest Territories and Yukon — while others have taken a more cautious approach by only offering them to certain vulnerable groups and health-care workers.
But the current case for rolling out third shots to most Canadians while much of the world remains unvaccinated and new variants continue to emerge seems weak at best.
“There is currently no evidence of widespread decreasing protection over time against severe disease in the general Canadian population who have been vaccinated,” a spokesperson for the National Advisory Committee on Immunization (NACI) told CBC News.
“NACI continues to actively review available evidence from Canada and other countries, and if needed, will update advice on booster doses as a preventive measure.”
‘Don’t want to wait until it’s too late’
Experts are divided over the need to expand access to additional shots to more Canadians — or even to everyone over 18 — and the emergence of the omicron variant will likely only heat up the debate further until we know more about it.
“I understand that mounting pressure to give more and more doses,” said Dr. Danuta Skowronski, epidemiology lead at the British Columbia Centre for Disease Control, whose research prompted Canada’s decision to delay second doses of COVID-19 vaccines.
“But I cannot say based on the current evidence that there is a clear and present danger or need or indication for an additional dose for the general population of adults at this time.”
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Skowronski said the latest data from B.C. and Quebec, released jointly as a recent preprint study that has yet to be peer reviewed, suggested mRNA vaccines were close to 95 per cent protective against hospitalization and over 80 per cent against any infection.
“Should we be attempting a preemptive strike to fend off a possible surge? Well, that kind of attitude is a slippery slope,” she said.
Rolling out boosters more widely is a “massive population-wide undertaking” that could set a bad precedent for future shots.
“We should only really make decisions ahead of the evidence if there is an urgent need to do so — otherwise we should be cautious in jumping the gun … and on what basis then do we make decisions about whether a fourth, or a fifth, or a sixth dose?”
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Researchers at the Institute for Clinical Evaluative Sciences (ICES) in Toronto also found most fully vaccinated people in Ontario were still highly protected against both infection and severe COVID-19 eight months after their second dose.
ICES’s vaccine estimates showed that while protection against symptoms dropped to just over 80 per cent — and to more than 70 per cent when including asymptomatic infections — prevention of hospitalizations remained high at more than 90 per cent.
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“So the question is, at eight months, is a vaccine effectiveness of 70-something per cent good enough? Or is that going to open the door to disaster?” said Dr. Jeff Kwong, an epidemiologist and senior scientist at ICES.
“We’re kind of in this precarious spot where we’re probably going to need boosters at some point, but whether we need them now is debatable — but you don’t want to wait until it’s too late.”
Millions of unused vaccine doses sitting in freezers
Canada is also sitting on a massive stockpile of vaccines compared to other countries — with close to six million in the national inventory according to PHAC — while over one million doses have reportedly already gone to waste since the rollout began.
“Right now, we should be offering boosters to everybody five months out of the second dose,” said Raywat Deonandan, a global health epidemiologist and associate professor at the University of Ottawa.
“There are millions going unused, and we’re at the point where we’re struggling to get that last 20 per cent of people to even accept their first dose. So for the rest of us that have two doses, let’s maximize our immunity.”
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Dr. Isaac Bogoch, an infectious diseases physician and member of Ontario’s COVID-19 vaccine task force, says it’s “well past time” to expand booster eligibility to Canadians over the age of 50 who are six months out from their second shot at the very least.
“It’s pretty fair to say that there is some degree of waning immunity against getting the infection, but most of the data we’ve seen demonstrates that two doses still provide significant protection against severe disease,” he said.
“But there is still value in reducing infection as well — it really can reduce amplification of the virus in the community, and you certainly can prevent some severe disease especially in the older cohort.”
The push for expanding boosters in Canada comes despite the World Health Organization‘s plea to wealthier countries to hit pause on widespread booster shots until at least 2022 in favour of vaccinating more of the unvaccinated world.
The omicron variant emerged in southern Africa, which has some of the lowest vaccination rates globally, highlighting a dire need for more doses on the continent.
But Bogoch says the two approaches don’t need to be mutually exclusive.
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“We can align with the WHO’s request for a moratorium on population-level booster vaccines until 2022 but also simultaneously use the vaccines that we have and act in a data-driven manner by providing third doses to the 50-plus crowd,” he said.
“It was time to do this several weeks ago — if not a month or two ago — because we are headed into fall and winter months, and we know cases are going to predictably rise at this time of year.”
Boosters won’t prevent global threat of variants
Canada’s COVID-19 reproductive rate has been sitting precariously close to one for months, meaning a surge in cases due to an increase in indoor gatherings during colder weather could lead to exponential growth.
“We are all at the cusp of either growth or the decline in cases — we’re just there,” said Dr. Leyla Asadi, an infectious diseases physician at the University of Alberta in Edmonton.
“And we are kidding ourselves if we think that there isn’t going to be a significant increase in contacts over the holidays. Of course, there will be, and of course, this will mostly be inside because we are living in Canada in the winter.”
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Despite the increased risk during the next few months, experts say the emergence of a new variant of concern also further highlights the need to vaccinate people in lower-income countries who have had much less access to vaccines.
“Why do we have a stockpile of vaccines when much of the world does not have access to a first dose?” said Dr. Zain Chagla, an infectious diseases physician at St. Joseph’s Healthcare Hamilton and an associate professor at McMaster University.
“The reality of the situation is Canada doesn’t make vaccines, and so, every dose that shows up on our soil is a dose that was not on someone else’s soil.”
Canada has committed to donating 73 million more COVID-19 vaccines to the developing world, with four million doses sent to the WHO’s COVAX program earlier this month, but Chagla says giving low-risk Canadians another dose undermines that progress.
Alyson Kelvin, an assistant professor at Dalhousie University in Halifax and a virologist at the Canadian Center for Vaccinology and the Vaccine and Infectious Disease Organization in Saskatoon, says that given the global threat of variants, it would be better for Canadians to wait for a variant-specific booster.
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A booster tailored to the delta, omicron or other variants that emerge in the future would likely be more useful than a third shot of a vaccine aimed at the original Wuhan strain of the coronavirus.
“We should take some of the vaccines that might come in for boosters and donate those so that we’re dividing them up more evenly and not taking everything for Canada,” she said.
“That would be a much better strategy than bringing vaccines in for boosters, when it’s not clear if it’s going to help our current pandemic situation.”