An external health advisory body responsible for providing information about immunization to the Public Health Agency of Canada is recommending provinces and territories to delay administering second doses of COVID-19 vaccine by as long as 16 weeks.
The National Advisory Committee on Immunization (NACI) released a statement Wednesday calling all jurisdictions in Canada to extend the administration interval between first and second doses of COVID-19 vaccine by four months.
“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 second dose of COVID-19 vaccine up to four months after the first,” NACI said in its decision.
The recommendation is based on population-based data and expert opinions from around the world, which suggest that the vaccines can remain effective beyond their original interval date, according to NACI.
“Current evidence suggests high vaccine effectiveness against symptomatic disease and hospitalization for several weeks after the first dose, including among older populations.”
The recommendation comes days after British Columbia announced it would extend the interval between the first and second doses by 16 weeks ?— which drew criticism from Canada’s chief science adviser, Mona Nemer, who called it a “basically population-level experiment.”
Currently, the two main suppliers of COVID-19 vaccines to Canada ?— Pfizer and Moderna ?— recommend less than 30 days between first and second doses, although the United Kingdom and Israel have extended the vaccine dose intervals by four months as well.
The NACI’s recommendation suggests that if all jurisdictions extend the interval to the same time period as British Columbia, more Canadians will be protected sooner, which is expected to increase health equity faster.
“Although effectiveness after two-doses will be somewhat higher than with one dose, many more people will benefit from immunization when extending the interval between doses in times of vaccine shortage; offering more individuals direct benefit and also the possibility of indirect benefit from increasing population immunity to COVID-19 disease,” the committee said in its recommendation.
NACI says Canada has secured enough vaccine supply after four months to provide everyone with a second dose and that it will continue to monitor the “effectiveness” extended dose intervals.
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Nicholas Pescod
