The COVID-19 vaccine developed by China's Sinovac Biotech has proven to be effective as much as completely effective for more serious cases, though at least 78 percent of the time in tests done in Brazil.

"The vaccine protected 100 percent of the participants in relation to severe COVID-19 cases. It protected 100 percent of the participants in relation to moderate cases in the high-risk population," said Dimas Covas, director of Brazil's Butantan Institute.

"We need this vaccine to reach the arms of the people," said he during a press conference on Jan 7. The institute has a deal with Sinovac to manufacture and distribute CoronaVac in Brazil and other Latin American countries.

"This is the toughest trial for a COVID-19 vaccine in the world and this is the most complete trial ever disclosed," said Covas, explaining that other vaccines have been tested with people that are less exposed to the virus. "Anvisa understood and was positive on the results."

Anvisa, the Brazilian healthcare regulator, was expected to accept an application for approval of CoronaVac.

Butantan and the government of the state of Sao Paulo said on Jan 7 that CoronaVac can be totally effective in preventing severe cases of COVID-19. Butantan performed the late-stage trials for the vaccine, testing it with the participation of 12,476 volunteer participants, including healthcare workers from 16 testing centers in eight states.

"The Butantan vaccine has a range of efficacy that goes from 78 percent to 100 percent in mild, moderate and severe cases," said Covas.

China has already sent enough raw materials to Brazil to make almost 11 million doses of the vaccine. Several states in Brazil, including the state of Sao Paulo, are relying on CoronaVac, other China-developed vaccine candidates or Sputnik V, developed by Russia's Gamaleya National Center of Epidemiology and Microbiology, to roll out vaccination programs but the issue has been politically charged.

Brazilian President Jair Bolsonaro has pinned his hopes on AZD1222, developed by AstraZeneca and the University of Oxford, which has been renamed COVID-19 Vaccine AstraZeneca.

On Dec 23, Butantan and Sinovac delayed releasing data for CoronaVac for two weeks to analyze results from trials being carried out in Brazil, Turkey, Indonesia and Chile. With different trial formats, the results have varied.

"I have no doubt that Anvisa will approve CoronaVac. The pressure on Bolsonaro to start vaccination is already very high and would worsen considerably if the population perceived political motivations regarding the approval of (vaccines) in Brazil," said Igor Patrick, director of communications at Observa China, an independent network of Portuguese-speaking China experts.