There is not enough data to know the effectiveness of the vaccines from Pfizer and Moderna if the 2nd dose is given beyond 42 days after the first, the public health of Canada said Thursday.
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If Quebec waits up to 90 days before administering second dosesThe provincial health authorities will therefore need to monitor the impact closely and collect data on it.
This was indicated by the Deputy Chief Public Health Officer of Canada, Dr. Howard Njoo, in a press briefing Thursday.
“In terms of efficacy with the interval between the two doses, we have enough data to say that yes, it is effective if we have an interval of up to 42 days. After 42 days, we don’t know, ”he said.
However, he recognized that the issue is real at the level of the variable flow of doses of COVID-19 vaccines arriving in Canada and that he understands that Quebec must make difficult choices.
A joint statement released Thursday by the chief medical officers of the provinces and the federal government also underlines the obligation of the provinces to document the effects that come with the choice of stretching the time between the two doses beyond 42 days.
“When deemed necessary for a program to increase the interval between doses beyond 42 days, based on specific epidemiological data and their impact, this program should closely monitor the observed effects and share the results regularly, which will be added to the ever-expanding evidence base ”, we can read.
According to what Dr. Njoo said, Quebec’s national director of public health, Horacio Arruda, endorsed the joint statement.
The Pfizer vaccine is designed so that 21 days separate the administration of the first and second dose. Moderna’s plan is 28 days apart.
However, with the unstable flow of the first deliveries, Quebec chose to postpone the administration of the second dose in order to distribute a first dose to as many people as possible.
Given the supply issues, the National Advisory Committee on Immunization (NACI) agreed that it was possible to delay the administration of the 2nd dose for up to 42 days. However, the government of François Legault announced Thursday that it will allow to wait up to 90 days.
In their joint statement, Chief Medical Officers across Canada say they support NACI’s recommendations. “The flexibility afforded by reasonable stretching of the dose interval up to 42 days, depending on operational needs, and the increased predictability of vaccine dose supply, supports our public health goal of protect high-risk groups as quickly as possible, ”he wrote.
Note that the number of doses arriving in Canada will increase significantly as of April. Major General Dany Fortin, responsible for logistics for the federal government, indicated that it will be around one million doses that will be sent per week.