A leading Chinese vaccine has been found to be 50.4 percent effective, according to the results of a late-stage trial in Brazil, serving a blow to the Chinese regime as it seeks to leverage the vaccine to bolster its global image. The results from Brazil’s state-funded Butantan Institute on Tuesday were just enough to pass the 50 percent threshold set by the World Health Organization for regulatory approval. It was far lower than initial claims announced last week that touted a 78 percent efficacy rate. CoronaVac, a vaccine developed by Beijing-based drugmaker Sinovac Biotech, is one of Brazil’s two immunization candidates. The government last week made a deal to purchase up to 100 million doses of the Chinese vaccine. The latest revelation has fueled skepticism about Chinese vaccines. Brazilian President Jail Bolsonaro, who in October vowed that “Brazilian people will not be anyone’s guinea pig,” said on Wednesday that he …