MONTREAL — Experts say delaying the second dose of some COVID-19 vaccines could lead to the emergence of new variants of the virus — but there s no sign it has happened yet. "It s a . . .
Veillette, who is a member of the federal government s COVID-19 vaccine task force, said there s a concern that the immunity provided by one dose of the Pfizer-BioNTech and Moderna vaccines is not as strong as you would get with two doses. That weaker immune response, especially in older people whose immune systems don t respond as well to vaccines, may favour the selection of variants, Veillette said in an interview Wednesday. Quebec has responded to Canada s COVID-19 vaccine shortage by delaying the second dose of the two-dose vaccines. Public health director Dr. Horacio Arruda has said he believes that giving more people a single shot will save more lives than giving fewer people two doses.