Federal and provincial health officials are poring over emerging data on the advantages and disadvantages of extending the time between shots of two-dose COVID-19 vaccines. But demand exceeds supply, so researchers in British Columbia and Quebec are studying what happens when the interval between doses is extended. But British Columbia went further on Monday, moving to a four-month interval for doses of the mRNA vaccines from Pfizer-BioNTech and Moderna. Pfizer-BioNTech's vaccine is meant to be given as two doses, 21 days apart, while Moderna recommends 28 days. But the COVID-19 vaccines haven't existed long enough to know.

Source: CBC News March 03, 2021 09:00 UTC