Preliminary data from a study in Brazil indicates that the COVID-19 vaccine developed by China's Sinovac Biotech is effective against the P1 variant of the coronavirus first discovered in Brazil, a source familiar with the study told Reuters on Monday.

The source, who did not provide data details, said the study had tested the blood of vaccinated people against the variant. CoronaVac, as the Sinovac shot is known, is the main vaccine currently being used to inoculate people in Brazil.