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Canadian scientists question decisions to delay second COVID vaccine doses

Last Updated Mar 10, 2021 at 9:56 am PDT

Francesca Paceri, a registered pharmacist technician carefully fills the Pfizer-BioNTech COVID-19 mRNA vaccine at a vaccine clinic during the COVID-19 pandemic in Toronto on Tuesday, December 15, 2020. THE CANADIAN PRESS/Nathan Denette

Group of scientists warns of impacts of pushing back second doses of COVID-19 vaccines

Letter to feds questions guidance saying it's ok to delay second doses of COVID-19 vaccines to up to four months

B.C. announced earlier this month that it would extend possible time between doses to up to four months

OTTAWA – A group of scientists has reportedly penned a letter to federal and provincial governments raising concerns and questions about delaying the second dose of COVID-19 vaccines.

The letter, a draft of which was obtained by Global News, warns of the impact of pushing back the second dose, noting Canada is the only country attempting this and that there is not enough data to back up this decision.

The outlet says the letter has been signed by leading scientists from a number of major health institutions. The letter has apparently been sent to the Public Health Agency of Canada, as well as the provinces of British Columbia, Ontario, and Alberta.

Dr. Jorg Fritz, an immunologist at McGill University, says he shares the concerns raised in the letter, likening the decision to delay second doses to “a big gamble” or “playing with fire.”

He also worries that if people are not fully protected, it increases the changes of the virus mutating.

“And that might cause, you know, increased risk of new variants,” he said, noting that could create the need for boosters and putting the vulnerable at risk once more.

B.C. was the first province to announce it would be extending the interval between first and second doses by up to four months. Alberta and Ontario followed suit, and the National Advisory Committee on Immunization has also released guidance in line with this decision.

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NACI said last week that this length of delay is acceptable in order to provide more wide-spread protection in situations where supply is limited.

Federal Chief Public Health Officer Dr. Theresa Tam has defended the advice of the committee, noting the four month delay is a maximum number, and not a requirement.

“It’s not to say we have to give it at four months, it’s just as fast as you can possibly then give that second round,” she said. “Increasing the flexibility of the ability of the provinces to deliver that first dose, which is really safe and effective, to as many people as possible to prevent deaths and hospitalizations.”

B.C. Provincial Health Officer Dr. Bonnie Henry has also defended her decision to extend the interval from the previous 42-day recommendation, saying the strategy is based on data.

“We are in a position where we are looking at the data from the U.K. but we are also in a position that’s quite different from the U.S. in terms of our vaccine availability in the short-term,” she explained on March 2, referencing other studies backing the move. “And we are at a position where we still have ongoing transmission in our communities in quite a serious way.”

Henry also noted that the benefits of delaying second doses isn’t limited to how many more people will receive the shot sooner, saying that the “timing of the booster dose can sometimes confer additional benefit in terms of the strength of the immune response, particularly the cell-mediated immunity and have a prolonged benefit in how long the response lasts.”

The federal government is holding a technical briefing on vaccine rollouts on Wednesday.