Brazil’s health regulator has suspended a clinical trial for China’s Sinovac coronavirus vaccine citing a severe adverse event, delighting President Jair Bolsonaro, who has criticised it for lacking credibility amid growing geopolitical tensions as the global race for a Covid-19 vaccine continues.

Brazil’s health regulator, Anvisa, said late on Monday that the event occurred on October 29 but did not specify if it took place in Brazil or in another country. It also did not give an indication of how long the suspension might last.

Anvisa’s decision surprised trial organisers, who said there had been a death but it was unrelated to the vaccine.

“As there are more than 10,000 volunteers at this moment, deaths can occur ... It’s a death that has no relation with the vaccine and as such it is not the moment to interrupt the trials,” Dimas Covas, the head of Sao Paulo’s medical research institute Butantan, which is conducting the Sinovac trial, told local broadcaster TV Cultura.

Brazil’s suspension of the trial, one of Sinovac’s three large late-stage studies, and the resulting fallout underlines the increasingly fraught political atmosphere surrounding the development and distribution of potential vaccines. The setback to Sinovac’s efforts contrasts with good news from Pfizer Inc.