Thailand's health ministry said on Sunday more than 600 medical workers who received two doses of China's Sinovac vaccine have been infected with Covid-19, as authorities weigh giving booster doses to raise immunity.

Of the 677,348 medical personnel who received two doses of Sinovac, 618 became infected, health ministry data from April to July showed. A nurse has died and another medical worker is in critical condition.

An expert panel has...