Pfizer, Moderna preferred the 2nd dose after AstraZeneca: Canadian authorities
Canada’s National Advisory Committee on Immunization said on Thursday that people who received the AstraZeneca vaccine as their first dose should be given Pfizer-BioNTech or Moderna for their second injection.
On June 1, the committee said AstraZeneca recipients could “get Pfizer or Moderna for their second injection if they wanted, but Thursday went further by saying an mRNA vaccine was the preferred choice.”
Since the advisory committee “first reviewed mixed vaccination schedules, new evidence begins to emerge suggesting that immune responses are better when a first dose of AstraZeneca vaccine is followed by an mRNA vaccine as the second. dose, âsaid its vice president, Dr. Shelley Deeks, in the new guidance documents.
The committee also updated its previous recommendation that people at high risk of exposure or severe illness from COVID-19 could opt for AstraZeneca rather than wait for Pfizer or Moderna. Now, he says everyone should always get mRNA vaccines first, unless they’re allergic to them.
Deeks said the advice was based on the growing supply from Pfizer and Moderna and the risk of vaccine-induced blood clots associated with AstraZeneca. But she still tries to reassure people who have received one or two doses of AstraZeneca vaccine that they are nevertheless well protected.
Anyone who has ever received two doses of AstraZeneca / Covishield can rest assured that they are protected, especially against serious illnesses, she said. “There is no need for a third dose at this time.?
Dr. Theresa Tam, Canada’s chief public health officer, said new evidence supporting mixing different types of vaccines included four studies in Germany.
“It’s really the immunogenicity, this immune response, after this mixed-dose schedule that led NACI to update this recommendation, because all of the accumulated studies basically suggest that the immune response is a better response,” said Tam at a press conference in Ottawa.
One such study from the German University of the Saar, on Wednesday released preliminary data indicating that administering Pfizer as a second dose after AstraZeneca, or two doses of Pfizer alone, generated significantly more antibodies and T cells than two doses of AstraZeneca.
Almost 25 million Canadians have now received at least one dose of the vaccine, and nearly 6 million are now fully immunized. As of June 5, 2.1 million people had received one dose of AstraZeneca and 15,186 had received two.
There are no further AstraZeneca shipments currently planned, but approximately 600,000 doses remain from previous shipments.
There are 14 million doses of Pfizer-BioNTech and Moderna to be delivered this week and next, including a donation of 1 million doses of Moderna’s COVID-19 vaccine from the United States due to arrive in Canada Thursday evening.
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