The Federal University of Sao Paulo, which is running the trials, said in a statement that 4,600 of the planned 5,000 volunteers have been vaccinated in Brazil without any of them reporting any serious health issues.

The volunteers have been recruited in Sao Paulo, Rio de Janeiro and Salvador in the northeastern state of Bahia where a hospital is conducting the tests.

AstraZeneca paused global trials temporarily last week after an unexplained illness in a participant in Britain.

Brazil has the third worst coronavirus outbreak after the United States and India and has become a sought-out testing ground for COVID-19 vaccines under development in Britain, China and Russia.

Phase III clinical trials of Russia’s Sputnik V vaccine against COVID-19 will be conducted in the Brazilian states of Bahia and Parana, which has plans to produce the vaccine for Brazil and other Latin American countries.

Phase III clinical trials of a vaccine developed by China’s Sinovac Biotech Ltd are under way in the state of Sao Paulo, whose governor said last week it may be available to Brazilians as early as December.

Some 9,000 Brazilian volunteers are participating in the Sinovac vaccine trials, which are being conducted by the Butantan Institute in Sao Paulo city and 11 other locations, including the capital Brasilia.

REUTERS