BNTX BioNTech SE

By Paul Vieira

OTTAWA--Canadian health authorities said Tuesday authorized Covid-19 vaccines are interchangeable, a decision partly motivated by the risk of blood clotting associated with a dose of AstraZeneca PLC's vaccine.

Letting people get a different vaccine for their second dose could also help Canada maintain its accelerated pace of inoculation, and reach its target of getting most of the population fully vaccinated by the end of September.

Some Canadian provinces, most notably Ontario, put a halt on the use of AstraZeneca's vaccine for a first dose due to the risk, while other provinces stopped because of a lack of supply. Canada's national advisory panel on immunization said messenger vaccines produced by Pfizer Inc., in partnership with BioNTech SE, and Moderna Inc. were preferred over viral vaccines, such as those from AstraZeneca and Johnson & Johnson.

The panel said Tuesday that, after reviewing available evidence, it was safe for people who received a first dose of AstraZeneca's vaccine to receive an mRNA vaccine, as produced by Pfizer-BioNTech and Moderna Inc., for their second shot. Some European countries, such as Germany and France, already allow people to receive a different vaccine for their second shot.

The panel added mRNA vaccines can also be mixed.

"It is expected that combining different Covid-19 vaccines that induce an immune response against [the new coronavirus] will lead to a robust immune response," the advisory panel said in its recommendation on mixing vaccines. While its recommendations aren't binding, they tend to be closely followed by the country's provinces, which have responsibility for delivering health care.

The panel said that because of AstraZeneca's safety profile and risk of blood clotting, "offering an alternative product with a more acceptable safety profile and expected comparable immunogenicity profile, while enabling individuals to make an informed choice, is ethically justifiable." The Public Health Agency of Canada has estimated the rate of a blood clot linked to the AstraZeneca vaccine in Canada to be one in 83,000 doses administered.

Over the past two months, Canada has sharply increased the administration of Covid-19 vaccines, with nearly 60% of the population having received one dose versus 14% at the start of April. However, Canada lags by a sizable margin the rest of the developed world in terms of the share of the population that is fully vaccinated, at 5%.

Over two-thirds of doses administered in Canada are from Pfizer-BioNTech, and the country is expecting deliveries of more than two million doses a week through June and July. Canadian officials say they expect millions of Moderna and AstraZeneca doses this month.

The panel said Canada is anticipating large supplies of mRNA vaccines in the summer months "that will be sufficient to complete the second dose in all age groups for whom immunization is recommended." Canadian officials have set the end of September as the date at which it is hoped the bulk of the population will be fully vaccinated.

Write to Paul Vieira at paul.vieira@wsj.com

(END) Dow Jones Newswires

June 01, 2021 13:38 ET (17:38 GMT)

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