Alberta may extend time between doses of COVID-19 vaccines

Alberta may follow British Columbia's lead and lengthen the time between administering first and second doses of COVID-19 vaccines, Health Minister Tyler Shandro says.

B.C. to wait up to four months between shots to get more residents first doses

In February 2020, Health Minister Tyler Shandro ended the province's master agreement with the Alberta Medical Association and imposed a new compensation framework for the province's doctors, sparking a bitter dispute. CBC has obtained a copy of the new tentative agreement between the two parties. (Government of Alberta)

Alberta may follow British Columbia's lead and lengthen the time between administering first and second doses of COVID-19 vaccines, Health Minister Tyler Shandro says.

Evidence from the United Kingdom, B.C., and Quebec suggests the first dose of the two vaccines currently being distributed in Alberta can provide 90-per-cent protection against the novel coronavirus that causes COVID-19, and that protection can last for months.

Alberta health officials and physicians are now reviewing that new evidence and examining whether the province can further delay second shots, Shandro said at a Tuesday news conference.

WATCH | Alberta Health Minister Tyler Shandro said Alberta is considering following B.C.'s lead when it comes to vaccines

Alberta may extend time between doses of COVID-19 vaccines

2 years ago
Duration 0:51
Alberta may follow British Columbia's lead and lengthen the time between administering first and second doses of COVID-19 vaccines, Health Minister Tyler Shandro says.

"It's going to give us an opportunity to get more people vaccinated more quickly, which is going to be fantastic news for Albertans," he said.

Dr. Deena Hinshaw, Alberta's chief medical officer of health, said Tuesday an expert panel hopes to make a decision soon about whether to extend the recommended window of time for second doses.

"As we're looking at decisions — as we are in Alberta — about how to best protect our population, that we're using real-world experience and real-world evidence and that we're making decisions based on that," Hinshaw said, referring people who received vaccines outside of clinical trials.

Infectious diseases doctor says now time to make the switch

Manufacturers' instructions say the Pfizer-BioNTech vaccine doses should be given 21 days apart and Moderna doses should be 28 days apart.

The National Advisory Committee on Immunization said prolonging the wait to 42 days is acceptable in places where there's high community transmission, strain on the health-care system and limited vaccine supply. Alberta guidelines currently recommend people receive their second shot within six weeks of their initial vaccination.

On Monday, B.C.'s provincial health officer said new evidence was prompting that province to extend the wait between doses for up to four months. That change, plus Health Canada's approval of a third vaccine, manufactured by AstraZeneca, would allow everyone in B.C. who wants a first dose to receive one by the end of July.

Alberta's plan aims to have mass vaccination by September.

Dr. Jim Kellner, a pediatric immunology specialist in Calgary and member of the national COVID-19 immunity task force, said the Alberta government should act fast if it wants to reap the potential advantages of delaying doses.

With a relative scarcity of COVID-19 vaccines available, postponing second doses could help grow the number of vulnerable people protected by a first dose, he said.

"Putting [the decision] off some number of weeks, a few months, isn't going to provide the benefit that we're looking for now, which is to provide as many doses as possible to those at highest risk," he said.

He said current evidence shows a six-week pause between shots for COVID-19 is fine. Predictions about the effect of delays any longer than that are based on knowledge of how other vaccines work, he said.

Vaccine manufacturers can't recommend off-label use, because they don't have clinical trial data to support it, he said.

It's important for people to ultimately receive that second dose, he said, as boosters for other vaccines have been shown to improve longer-term protection against disease and better prevent asymptomatic spread.

Alberta could also shorten its recommended dose gap when vaccine supplies improve, he said.

Dr. Lynora Saxinger sits in front of a desk, as she is interviewed.
University of Alberta infectious diseases expert Dr. Lynora Saxinger said she would have been comfortable waiting longer for a second dose of her COVID-19 vaccine, knowing the first dose offers good protection within a couple of weeks. (CBC)

Edmonton infectious diseases expert Dr. Lynora Saxinger, co-chair of the COVID-19 scientific advisory group to Alberta Health Services, says the decision is a gamble on how long that first shot offers adequate immunity.

Even with vaccines less effective than the ones Alberta has received, some modelling has shown that waiting longer between doses to inoculate more people would save more lives, she said.

"I think people have concerns that they're not adequately protected after one dose, and I can see how that would create some anxiety," she said. "But the actual literature really suggests that that excellent protection against hospitalization, death, severe disease, really does start quite early after the first dose."

If vaccine supplies slow down, it would be reasonable to look at a three- or four-month delay between shots, she said.

"You want a strategy where you're vaccinating the highest-risk people with at least their first dose as quickly as possible."

More important is a health system being agile enough to change the timing of vaccine doses, should new evidence emerge, she said.

As of Monday, 88,539 Albertans had received two doses of a COVID-19 vaccine, according to Alberta Health. Nearly 68,000 Albertans have received a single dose.


Janet French

Provincial affairs reporter

Janet French covers the Alberta Legislature for CBC Edmonton. She previously spent 15 years working at newspapers, including the Edmonton Journal and Saskatoon StarPhoenix. You can reach her at janet.french@cbc.ca.

With files from Canadian Press


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