A COVID-19 vaccine developed by China's Sinovac Biotech was 78 per cent effective in a late-stage Brazilian trial and entirely prevented severe cases, a source said on Thursday, boosting Chinese efforts to catch up with Western vaccine makers.
The reported results, closely watched by developing countries counting on the vaccine to begin mass inoculations, come after Turkish researchers said in December that the vaccine showed 91.25 per cent efficacy based on interim data.
Brazil and Indonesia, which have the most COVID-19 cases in Latin America and Southeast Asia respectively, are preparing to roll out the vaccine, called CoronaVac, this month.
Although CoronaVac's efficacy trails the more than 90 per cent success rate of vaccines from Moderna Inc or Pfizer Inc and its partner BioNTech SE, it is easier to transport and can be stored at normal refrigerator temperatures.
Turkey, Chile, Singapore, Ukraine and Thailand have also struck supply deals with Sinovac.
The company's Brazilian partner, biomedical center Butantan, presented the efficacy data to federal health regulator Anvisa and sought approval for emergency use of the vaccine in a Thursday meeting, according to a person familiar with the study who spoke anonymously because the data remains confidential.
Anvisa and Butantan declined to comment on the efficacy data or conclusions from the meeting. The Sao Paulo state government, which runs the Butantan Institute, planned a news conference at 12:45 p.m. (1545 GMT) to discuss the results.
The findings, first reported by newspaper Folha de S.Paulo, are based on a study led by Butantan involving about 13,000 volunteers, with half receiving a placebo and half taking the two-dose vaccine.
Brazil's CoronaVac trial included elderly volunteers, unlike other studies of the vaccine, and was the first to present final efficacy data. None of those who received the vaccine had severe or moderate cases requiring hospitalisation, the source said.
China has at least five vaccines, developed by Sinovac, Sinopharm, CanSino Biologics and the Chinese Academy of Sciences, in late-stage trials, underscoring its efforts to develop a homegrown vaccine to challenge Western rivals.
Since the new coronavirus emerged a year ago in a market in the central Chinese city of Wuhan, President Xi Jinping has pledged to make China's vaccines a global public good.
The positive data follows China's approval on Dec. 31 of a vaccine developed by an affiliate of Sinopharm that showed 79.34 per cent efficacy, pointing to progress China has made in the global race to develop successful vaccines.
Although China has been slower than several other countries in approving the vaccines, it has inoculated more than 2.0 million people since July under an emergency use program, using three different shots from Sinovac and Sinopharm that are still undergoing late-stage trials.
In Brazil, President Jair Bolsonaro has expressed disdain for the Sinovac vaccine, citing doubts about its "origin" and trading barbs with political rival João Doria, the governor of Sao Paulo, which is funding trials and production of the shot.
Brazil has the world's second-deadliest outbreak after the United States and aims to vaccinate 51 million people, or about one-fourth of its population, in the first half of 2021, although immunisations have not yet begun.