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National panel OKs mixing and matching COVID-19 vaccines

New recommendations come amid AstraZeneca supply crunch
The National Advisory Committee on Immunization says it's OK to receive the Pfizer or Moderna COVID-19 vaccine as your second dose if your first was AstraZeneca.

The National Advisory Committee on Immunization (NACI) says Canadians who received the AstraZeneca plc COVID-19 vaccine for their first dose can consider getting jabbed with either the Pfizer Inc. or Moderna Inc. vaccines for their second dose.

Health officials at both federal and provincial levels have said it’s preferable Canadians are inoculated with the same product for both doses but the new recommendations now offer flexibility.

Canada is facing supply issues with AstraZeneca, which is a viral vector vaccine, while messenger RNA (mRNA) vaccines like Pfizer and Moderna have made up a far more significant portion of the country’s supply.

“It’s a practical issue,” Dr. Theresa Tam said through a French translator during a Tuesday media briefing.

She said the first group of Canadians to receive the AstraZeneca vaccine got their shots about 12 weeks ago — close to the 16-week window NACI recommends for the interval between first and second doses.

In recommendations released on Tuesday, NACI said Canadians who received AstraZeneca for their first shot may receive AstraZeneca for their second shot or else an mRNA vaccine for their second shot.

"This is not a new concept. Similar vaccines from different manufacturers are used when vaccine supply or public health programs change. Different vaccine products have been used to complete a vaccine series for influenza, hepatitis A, and others," the committee said in its recommendations.

But it’s not a two-way street

“Persons who received a first dose of an mRNA vaccine (Pfizer-BioNTech or Moderna) should be offered the same mRNA vaccine for their second dose,” NACI said.

If the same mRNA vaccine is not readily available, another mRNA vaccine can be considered interchangeable, according to NACI.

“While it is always preferable to have the same product for the first and second doses, in some cases, that isn't possible. There are a number of reasons for this: People can have an adverse reaction to those, or they simply don't know [which vaccine they received first] or that vaccine may not be available,” B.C. provincial health office Dr. Bonnie Henry said last week.

“I want to assure people that we will have enough of the AstraZeneca vaccine to provide second doses for everybody who wants that.”

Henry and B.C. Health Minister Adrian Dix are expected to speak on Thursday about B.C.’s plans for mixing and matching vaccines.

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