Canada has decided to go in for a mixing and matching of AstraZeneca, Pfizer and Moderna COVID-19 vaccine doses to adjust for available supplies.
The National Advisory Committee on Immunization (NACI) updated its guidance based on early research from UK, Spain that shows mixing shots of AstraZeneca and Pfizer vaccines was both safe and effective at preventing COVID-19. It recommended that a first shot of the AstraZeneca vaccine can be followed by either Moderna or Pfizer, according to an ANI report from Ottawa.
For Canadians who have had a first dose of Moderna or Pfizer, NACI recommended they can now take either of the two shots as a second dose if the same first dose is unavailable or unknown. This is because they both use a similar mRNA technology.
The details of the shift in guidance were confirmed publicly by officials from the Public Health Agency of Canada during a news conference Tuesday afternoon, Canada's Chief Public Health Officer Dr Theresa Tam said the decision to combine mRNA vaccines interchangeably was "nothing new" and that the same principle had been applied to different types of vaccines in the past — including shots for influenza and Hepatitis A, according to CBC News.
"This is not a new concept, so having a multi-dose series in terms of vaccines given by manufacturers is something that public health have used over time for many other vaccines," Tam said. "When vaccines programs and supplies change this is not an unusual thing to do."
The updated NACI recommendations stated, "No data currently exist on the interchangeability of COVID-19 mRNA vaccines," but Tam said there are "ongoing studies" on the effectiveness of the approach that have yet to be published. The decision was made based on the similar makeup of the vaccines, which both target the spike protein of the coronavirus, she said.
The updated guidelines follow moves by some Canadian provinces to combine different shots due to issues with the supply of AstraZeneca.
More than 13 million people have received at least one dose of the Pfizer vaccine in Canada, in contrast to over 3.5 million of the Moderna vaccine and more than 2.1 million of the AstraZeneca vaccine as of May 22, according to the latest available federal government data.
