A medical worker prepares a dose of COVID-19 vaccine at a drive-thru vaccination site in Toronto, Canada, on May 22, 2021. About 50.08 percent of Canada's population were administered with the first dose of COVID-19 vaccine and 4.3 percent with second dose as of Saturday afternoon, according to CTV. (Photo by Zou Zheng/Xinhua)

A man wearing a face mask walks past a poster displaying information about the COVID-19 vaccination in Toronto, Canada, on May 22, 2021. About 50.08 percent of Canada's population were administered with the first dose of COVID-19 vaccine and 4.3 percent with second dose as of Saturday afternoon, according to CTV. (Photo by Zou Zheng/Xinhua)

A man receives a dose of COVID-19 vaccine in his vehicle at a drive-thru vaccination site in Toronto, Canada, on May 22, 2021. About 50.08 percent of Canada's population were administered with the first dose of COVID-19 vaccine and 4.3 percent with second dose as of Saturday afternoon, according to CTV. (Photo by Zou Zheng/Xinhua)