Canada will have enough AstraZeneca COVID-19 vaccines for a 2nd shot: officials

Federal officials say there will be enough supply of the AstraZeneca COVID-19 vaccine for any Canadian who wants to use it for their second dose.

“We want to assure everyone that sufficient supply will be available for those who want a second dose of AstraZeneca or who can not take a mRNA vaccine,” said Maj.-Gen. Dany Fortin, who is leading Canada’s vaccine rollout.

Canada is expected to receive 655,200 doses of the AstraZeneca vaccine between May 17 and May 21.

The reassurance comes after Ontario, Quebec, B.C., Alberta and New Brunswick have made the vaccine no longer available as a first dose due to supply concerns and the potential risk of a rare blood clotting reaction called vaccine-induced thrombotic thrombocytopenia (VITT).

Out of 2.3 million doses of the AstraZeneca vaccine administered in Canada to date, 28 suspected cases of VITT have been reported, according to the federal government. Canada’s National Advisory Committee on Immunization (NACI) says the estimated risk of VITT is about one in 100,000 people.

Last week, NACI said that the mRNA vaccines by Pfizer-BioNTech and Moderna were “preferred” over the AstraZeneca or the Johnson & Johnson shots.

While few have received the second dose of AstraZeneca in Canada, in the U.K., about 4.4 million have done so. Of those, about four cases of blood clotting were reported.

Data is still coming in as to the effects of mixing two different vaccines for first and second doses.

Deputy Chief Public Health Officer Dr. Howard Njoo said Thursday that mixing vaccines could even provide a “greater” immune response, providing “broader protection against COVID-19.”

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Preliminary data from a University of Oxford study found that mixing the Pfizer-BioNtech and AstraZeneca vaccines is safe, but may increase the frequency of mild to moderate side effects.

The symptoms, though, lasted for a few days at most and there were no hospitalizations.

According to the study, 34 per cent of 110 participants who received a first dose of AstraZeneca and a second dose of Pfizer reported feverishness, compared to 10 per cent of 112 participants who had a first and second dose of AstraZeneca.

However, the study used a four-week interval between doses, whereas most of Canada will use a 12-week interval.

Another concern is the effect of mixing a mRNA vaccine with one that does not use the new technology, such as the AstraZeneca vaccine, which chief public health officer Dr. Theresa Tam said Canada will be watching “very closely.”

Njoo said Canada will review data from the U.K. studies seek guidance from the National Advisory Committee on Immunization (NACI) before providing recommendations for a second dose for those who received a first dose of AstraZeneca.

Prime Minister Justin Trudeau received a first dose of AstraZeneca and said he will take it as a second on the advice of his doctor, and Ontario Premier Doug Ford has expressed willingness to take it as a second dose as well.

— With files from Emerald Bensadoun, Rachael D’Amore and Reuters