An experiment conducted by University of Sao Paulo in the Municipality of Serrana in the State of Sao Paulo, Brazil demonstrated the effectiveness of COVID vaccination against the predominant P.1 variant of SARS-CoV-2 virus.  In the trial, 27,000 adult residents received two doses of CoronaVac over an eight week period.  In the following months, symptomatic cases of COVID declined by 80 percent, hospitalizations by 86 percent and deaths by 95 percent.  In comparison, in fifteen other cities in the vicinity, cases and fatalities soared.

CoronaVac, approved by the World Health Organization, is manufactured in Brazil by the Butantan Institute under license from China.