One of Canada’s top health officials said Friday that Canada may recommend next year for all adults to have a third dose of a COVID-19 vaccine, but the timing of such a rollout is important.
“At some point next year there might be a recommendation for everyone to have a third dose,” said Public Health Agency of Canada’s deputy chief public health officer, Dr. Howard Njoo.
“We need to do a risk-benefit or cost-benefit analysis because it would be a big decision to have a third dose for everyone,” he said.
“We don’t want to administer third doses too early but we also don’t want to wait too long to administer the third dose … we don’t want to wait until such a time there are too many cases among vaccinated people.”
Health Canada has recently approved both Pfizer and Moderna’s COVID-19 vaccine boosters for all adults over 18 years old, but Canada’s National Advisory Committee on Immunization (NACI) has not yet recommended booster shots to the general population.
A third dose for those 18 years of age and older has been approved in Manitoba, whereas Ontario has approved it for those 70 and older, health-care workers and essential caregivers in congregate settings, as well as those who received two shots of the AstraZeneca vaccine and Indigenous residents.
Quebec also recently expanded eligibility for those 70 and older and the Yukon, where cases are surging, is making it available for those 50 and over.
Queen’s University Infectious disease professor Dr. Gerald Evans believes that a third dose will be recommended for all adults at some point in order to “get the maximum benefit from vaccines.”
“A third dose is useful,” he said.
“It’s almost certain that the third doses are likely to be needed for pretty well everybody because we know there’s lots of vaccines we use where three doses is clearly better than two,” pointing to the hepatitis B vaccine as one example.
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Evans said that the best time for a third dose could be between six and nine months after the second, depending on one’s health and age.
He said, though, that if Canada waits too long for a third dose, that could mean “less control over cases” and an inevitable rise in their numbers.
“Whenever case numbers rise, there’s always the potential that it’s going to happen in somebody who has other conditions that then would make that COVID case put them into hospital,” he said.
“If we delay too long, we need to be very careful because it could result in increased hospitalizations again, and of course, ultimately, the bad stuff [of] dying of COVID.”
Evans stressed, though, that the data so far shows that two doses still provide very good protection — of about 90-95 per cent — from severe illness for the general population and about 85 per cent protection from contracting the virus at all.
He said that the risks of taking a third dose appear to be the same as that of getting the second, according to the preliminary data available.
He pointed out that growing evidence shows that a longer interval of eight to 12 weeks between the first and second doses of vaccine actually provides better protection than those who received two doses in quicker succession, such as in the U.S. and Israel.
This allows Canadians, who mostly had longer intervals, to take more time to roll out third doses, Evans said, especially when those over 18 only got their shots over the summer as opposed to earlier.
“One of the reasons why we may have done very well so far in what looks like a fourth wave is that that longer interval really protected us longer than the shorter interval was protecting people in countries where that was the norm versus what we did here,” he said.
Evans believes Manitoba has already allowed third doses for all adults simply because it is easier for them to orchestrate, especially since it has a smaller population.
“Governments don’t like to spend forever and ever and if they’ve got adequate supplies of vaccine, and they certainly want to get it into arms before it expires,” he said.
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