COVID-19 vaccine changes: Why Canada went from 3 weeks to 4 months between doses

Elisabetta Bianchini
·2 min read

Dr. Howard Njoo, Canada’s deputy chief public health officer, spoke about the recent change in guidance from the National Advisory Committee on Immunization (NACI) on the time between two COVID-19 vaccine doses, and how that may contribute to vaccine hesitancy in Canada.

On Wednesday, NACI publicly determined that the interval between the first and second doses of COVID-19 vaccines can be extended to four months.

"While studies have not yet collected four months of data on vaccine effectiveness after the first dose, the first two months of real world effectiveness are showing sustained high levels of protection," the NACI information reads.

"NACI recommends that in the context of limited COVID-19 vaccine supply, jurisdictions should maximize the number of individuals benefiting from the first dose of vaccine by extending the interval for the second dose of vaccine to four months."

This also comes after it was recommended that seniors 65 and older do not get the AstraZeneca vaccine, due to concerns around effectiveness.

Dr. Njoo stressed that the initial approvals of the Pfizer-BioNTech, Moderna and AstraZeneca vaccines were based on clinical trials, before real world data was available.

"Now as we’re actually accumulating real world evidence in terms of the experience form multiple countries around the world, U.K., United States, Israel and so on,...its been shown to that you get very good protection after the first dose," he said.

"The other point also is that the second dose, just in terms of general principles of vaccinology and immunology, has shown to sort of boost...the length of protection. But certainly based on the experience and the data we have to date, that obviously NACI’s looked at, there’s been no drop off significantly in terms of the [duration of protection.]"

Dr. Supriya Sharma, senior medical advisor with Health Canada, added that there are concerns about Canadians having vaccine hesitancy but it's important for the public to understand that guidance and recommendations around vaccines is going to change.

"We have multiple vaccines that are authorized, we have huge mass vaccination campaigns that are ongoing around the world and the responsible thing to do is to make sure that we get all that information and incorporate that into our decision making," Dr. Sharma said.

Dr. Njoo stressed that everyone also has a responsibility to not get sucked in by "click bait" information around COVID-19 vaccines.

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