To cover more ground with limited vaccines, and to save more lives, she endorsed a policy of delaying the second dose by four months. (Three of the four vaccines currently approved in Canada are based on two-dose regimens between 21 and 28 days.)
A couple of days later the National Advisory Committee on Immunization strongly recommended that the rest of the country follow suit. Surprisingly, they did.
As researchers at B.C.’s Royal Columbian Hospital later put it: “While there are no large clinical trial published data to guide prolonged delays of the second dose, there are data to suggest that delaying the second dose likely preserves the long-term boost in immunity without an unacceptable decrease in immunity in the intervening period between doses.”