Why Canada’s big bets on delaying, mixing doses of COVID-19 vaccines could pay off – CBC

Shifts away from manufacturer recommendations still rooted in vaccine science, experts say

May 17, 2021

While the typical approach for COVID-19 vaccinations is using the same brand for each dose, given at specific intervals, Canada has been exploring mixing doses on top of delaying second shots up to four months — two big bets that could pay off.

Before vaccine shipments started ramping up, Canada’s National Advisory Committee on Immunization (NACI) issued a bold recommendation to delay second doses well beyond manufacturing guidelines to a maximum of four months.

The move sparked criticism that Canada was engaged in a “population level experiment,” with concerns ranging from a lack of data, to a growing body of research suggesting it’s not the safest approach for immunocompromised and older adults.

Layered on that controversial move are more recent shifts toward mixing doses — including offering up an mRNA-based option, from Pfizer-BioNTech or Moderna, to some Canadians who have already gotten a first shot of AstraZeneca-Oxford.

Read more: https://www.cbc.ca/news/canada/toronto/canada-covid-vaccines-moderna-pfizer-1.6027657

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