SAO PAULO: Brazilian President Jair Bolsonaro said on Wednesday he was right to criticize the credibility of a Chinese COVID-19 vaccine developed by Sinovac Biotech that posted disappointing efficacy results in local trials.

On Tuesday, researchers in Sao Paulo state announced that the Chinese vaccine was 50.4% effective at preventing symptomatic infections in a local trial - barely enough for regulatory approval and well below the rate announced last week.

Bolsonaro, a far-right former army captain, is a longstanding China hawk. He has repeatedly criticized the Sinovac shot, which was being late-stage tested by Sao Paulo's Butantan Institute, as untrustworthy. He previously said his government would not buy the Chinese vaccine but later relented as criticism of Brazil's vaccine rollout has grown.

Speaking to supporters outside his residence, Bolsonaro made light of Sinovac's trial results so far, saying he had been unfairly maligned for questioning the shot.

"This 50% is good, is it? All the (criticism) I got for my comments, and now they are seeing the truth. Four months of being lambasted because of the vaccine," he said.

Nonetheless, Bolsonaro said he had no role in greenlighting the Sinovac shot as it was up to federal health regulator Anvisa to decide on whether to approve it for use.

Last week, Brazil's government closed a deal with the Butantan Institute to buy up to 100 million doses of the Chinese vaccine. The government will receive an initial 46 million doses with another 54-million dose option later.