In a controversial decision, the Brazilian state of Bahia has signed a deal with Russia to begin trials of its COVID-19 vaccine, Sputnik V, after it showed signs of an immune response.

"The government of the state of Bahia signed a confidentiality agreement on Tuesday to gain access to scientific data on the COVID-19 vaccine developed in Russia," the Folha de Sao Paulo newspaper reported.

A source in the Bahian government told Reuters that the state intends to buy 50 million doses of the vaccine. 

The Sputnik V vaccine was developed by Moscow’s Gamaleya Research Institute and was approved on Aug. 11 by the Russian Ministry of Health. 

An early study of the Russian vaccine, published in the Lancet medical journal, found that it caused a strong immune response in 76 trial participants. However, this data on immune response alone would not be enough for western regulators to approve the vaccine.

In August, Science Magazine examined the problems related to the Russian vaccine: "Scientists around the world immediately denounced the certification as premature and inappropriate, as the Gamaleya vaccine has yet to complete a trial that convincingly shows it is safe and effective in a large group of people," it noted.

“We have no idea whether this vaccine is safe or whether it works,” Ashish Jha, Dean of the Brown University School of Public Health, said about the Russian vaccine. “It is really worrying when people start to bypass the standard process we have for vaccine development.”

Brazil is in dire need of an effective vaccine, with the country having the third-highest number of COVID-19 cases in the world, behind India and the United States. As of Thursday at 8:45 p.m. ET, Brazil has 4,238,446 COVID-19 cases and 129,522 deaths.

Brazil has rejected the idea of mandatory vaccinations to fight its COVID-19 outbreak. 

“No one can force anyone to get a vaccine,” Brazilian President Jair Bolsonaro said in a Facebook live video chat last week.

Bolsonaro has frequently downplayed the virus, and feuded with governors who have implemented shutdown orders to stem the spread of infection.