June 1, 2021
Canada’s National Advisory Committee on Immunization (NACI) has updated its guidance, recommending that approved COVID-19 vaccines can be safely mixed and matches in most scenarios.
Under the new recommendations released June 1, people who received a first dose of the AstraZeneca vaccine may receive an mRNA vaccine — Pfizer-BioNTech and Moderna — for their second dose, unless contraindicated.
But it is not recommending AstraZeneca after a first shot of Pfizer or Moderna.
People who have received a first dose of an mRNA vaccine should be offered the same vaccine for their second dose, NACI said. But mRNA vaccines can be interchangeable if the same product is not readily available for the second dose, it added.
In either case, the previous dose should be counted, and the series need not be restarted, the guidance stated.
The recommendations were based on a range of factor — from safety concerns to vaccine supply, Theresa Tam, Canada’s chief public health officer, said during a news conference Tuesday.
“The interchangeability of vaccines means that you can receive one vaccine product for your first dose and then safely receive a different vaccine for your second dose to complete your two-dose vaccine series for optimal protection from COVID-19,” Tam said.
“This advice provides provinces and territories with effective options to manage their vaccine programs,” she added.
“It’s good news that people now have the choice.”
Early data from studies in Europe suggests that mixing doses of COVID-19 vaccines is safe and effective.