Canada’s National Advisory Committee on Immunization (NACI) has announced its updated guidance to allow mixing and matching approved Covid-19 vaccines in most scenarios.
Four vaccines, developed by Pfizer, Moderna, AstraZeneca and Johnson & Johnson, have been authorised for use in Canada to date.
For Canadians who have had a first dose of Moderna or Pfizer, NACI recommends they can now take either of the two shots as a second dose — because they both use a similar mRNA technology — if the same first dose is unavailable or unknown.
While NACI is advising that the shots can be safely used in combination, it is recommended that Canadians should try to get the same dose in a series if possible, specifically when receiving Pfizer or Moderna.
The updated NACI guidance is based on emerging research from Spain and the United Kingdom that found mixing and matching AstraZeneca and Pfizer was both safe and effective in preventing COVID-19.
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.
No mixing of vaccines in India
The central government on Tuesday clarified that there will be no mixing of Covid-19 doses in India until enough scientific evidence on its effectiveness is gathered. It also clarified that there is no change in its SOP for vaccination, and all beneficiaries will get two doses of Covishield or Covaxin.
Head of a government-appointed expert panel recently said India may begin testing to determine whether mixing two doses of different Covid-19 vaccines could boost immune response.
