Canadians who got a first shot of AstraZeneca are now being advised to get a second shot of Pfizer or Moderna, known as an mRNA vaccine.
The recommendation comes from the National Advisory Committee on Immunization which says a mixed dose of AstraZeneca and an mRNA vaccine will provide greater immunization against COVID-19.
As well as having better inoculation against the virus NACI says there is a risk of developing a rare blood clot after the second shot of AstraZeneca.
Since May, provinces have stopped giving AstraZeneca as a first shot but have continued to provide it as a booster shot.