Covid-19: Injection of a second dose of a vaccine other than the first is allowed in Canada

On Tuesday, a scientific committee advising the Canadian government on vaccination gave the green light to replace the Covid vaccine from the first dose to the second dose. People who receive their first dose of AstraZeneca can receive either a second dose of the same drug or a dose of messenger RNA vaccine (Pfizer-BioNTech or Moderna), the National Advisory Committee on Immunization (CCNI) said in a press release. Canadians receiving the first dose of messenger RNA vaccine should be offered the same serum for the second dose, but if not available, a different messenger RNA vaccine may be offered.

“Vaccine interchangeability means you can get the first dose of vaccine and safely receive another vaccine for the second dose to complete the series of vaccines needed to provide optimal protection against Covid-19,” said Dr. Howard Nju, deputy head of the Federal Sanitary Inspector.

In formulating this recommendation, NACI indicates that it has, in particular, taken into account the risk of serious blood clots when using the AstraZeneca vaccine. It also indicates that such a mixture may lead to “the possibility of increasing short-term side effects (…), in particular headaches, fatigue and general malaise.” The combination of vaccines from different manufacturers is not new: it has been used against influenza or hepatitis A, the committee explains.

“We don’t want vaccine doses to go unused.”

“I believe we’ll have to take a close look at what happens after this recommendation,” said Dr. Teresa Tam, chief public health officer, when asked about the risk of Canadians avoiding the second dose of AstraZeneca vaccine. “We don’t want vaccine doses to go unused,” she added.

The provinces of Canada must decide whether to apply this recommendation or not. Some of them announced in May their decision to suspend the AstraZeneca drug as a precautionary measure for people receiving their first dose of the vaccine due to the increase in thrombosis associated with the vaccine.

But it continues to be used by people who have received their first dose of AstraZeneca and want a second dose of the same product.

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