News Vaccine Committee recommends “mixing doses” after first shot of AstraZeneca SHARE ON: Mohamed Fahim, staff Thursday, Jun. 17th, 2021 Photo provided by AstraZeneca 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.