More than a dozen doctors in Indonesia have died of COVID-19 even after receiving shots of China’s SinoVac vaccine, a medical association said.

Dr. Adib Khumaidi, who leads the COVID-19 mitigation group of the Indonesian Medical Association, said 401 doctors have died since the coronavirus pandemic began. At least 20 of the doctors who died were fully vaccinated with SinoVac’s jab, with 10 of the deaths occurring in June alone, The Wall Street Journal reported.

The development raises questions about the China-made vaccine that is being administered in several countries across the world.

According to the medical association, around 90% of Indonesian doctors — roughly 160,000 in all — have been given SinoVac’s shot, the report said.

Epidemiologists are now calling for an investigation into the deaths of medical workers to determine whether other factors, such as poor hospital care or pre-existing illnesses, played a role.

Studies conducted earlier this year found that SinoVac was successful in preventing COVID-19 hospitalizations or deaths. 

In Brazil, researchers found the shot to be 50% effective in preventing severe cases of COVID-19. 

In Chile, the vaccine shot was found to be 67% effective in preventing symptomatic infections, 85% effective in preventing hospitalizations, and 80% effective in preventing COVID-19 deaths.

"It's a game-changer for that vaccine and I think it ratifies quite graphically the discussion over its efficacy," Rodrigo Yanez, Chile’s vice trade minister, told Reuters in April. 

With that being said, there is very little research on the effectiveness of the SinoVac vaccine against the more contagious Delta variant. It isn’t known how many of the Indonesian doctors who died this month were infected with the highly transmissible strain.