After two doses, no cases of symptomatic Covid-19 were observed in the vaccine group compared to four cases in the placebo group, meaning the shots were 100 percent effective.

Adolescents are less likely than adults to contract the illness.

U.S. intelligence agencies are examining reports that researchers at a Chinese virology laboratory were seriously ill in 2019 a month before the first cases of COVID-19 were reported, according to U.S. government sources who cautioned on Monday that there is still no proof the disease originated at the lab.