A key federal advisory committee is no longer recommending that Canadians receive a second dose of the AstraZeneca vaccine.
The National Advisory Committee on Immunization (NACI) previously said that people who received a first dose of AstraZeneca could get it as their second or could choose an mRNA vaccine, such as Pfizer or Moderna.
But new guidance released Thursday said the Pfizer or Moderna vaccine is “now preferred” for the second dose.
“This change is based on emerging evidence indicating a potentially better immune response from this mixed vaccine schedule and to mitigate the potential risk of VITT associated with viral vector vaccines,” Dr. Theresa Tam, Canada’s chief public health officer, said in a news conference.
VITT is a rare blood clot that has occurred in some people who received the AstraZeneca shot.
NACI also recommended that an mRNA vaccine is preferred as a first dose unless one is inaccessible or there is a contraindication, for example, an allergy to an mRNA vaccine or its components.
“I wish to emphasize that people who received two doses of the AstraZeneca/COVISHIELD vaccine can rest assured that the vaccine they received provides good protection against infection and very good protection against severe disease and hospitalization,” said Tam.
NACI is now also recommending that people who received Pfizer or Moderna as their first dose should be offered the same vaccine for their second.
Tam said if the same vaccine is not readily available, the mRNA vaccines are considered “interchangeable,” meaning a person can be offered another mRNA vaccine instead.
