Canada: Pfizer, Moderna preferred 2nd dose after AstraZeneca

OTTAWA, Ontario -- Canada's National Advisory Committee on Immunization says it is now recommending people who got the AstraZeneca vaccine first should get Pfizer-BioNTech or Moderna for their second shot.

Previously, the committee had said AstraZeneca recipients could choose whether to get a second dose of the same vaccine, or an mRNA vaccine. But in new guidance released Thursday, it said Pfizer or Moderna are now “preferred” as the second dose.

The guidance is based on growing evidence that a second dose of an mRNA vaccine produces a stronger immune response, and because of the low but serious risk of vaccine-induced blood clots associated with getting AstraZeneca.

The advice doesn’t mean people can’t still choose AstraZeneca if they want, or if they are allergic to the mRNA vaccines.

“People who received two doses of AstraZeneca/COVISHIELD vaccine can rest assured that the vaccine provides good protection against infection and very good protection against severe disease and hospitalization,” the advisory committee said.

As of June 5, 2.1 million Canadians had received one dose of AstraZeneca, and 15,186 had received two doses.

There are no further shipments of AstraZeneca scheduled, but there are still about half a million doses of it in provinces.

There are 14 million doses of Pfizer-BioNTech and Moderna being delivered this week and next, including a donation of 1 million doses of Moderna’s COVID-19 vaccine from the United States that arrived in Canada on Thursday.

The donated doses are part of an American promise to donate 80 million doses of vaccines by the end of June.

Jeff Zients, the White House COVID-19 response coordinator, said the shipment to Canada followed one to Mexico on Tuesday.