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Third time's the charm? Brazil scales back efficacy claims for COVID-19 vaccine from China

A more detailed analysis that included trial participants who tested positive but had symptoms so mild they did not seek help found 167 cases of COVID-19 in the placebo group and 85 in people who received the vaccine, for an estimated efficacy of 50.34%. Even allowing for statistical uncertainties, that is considerably below the greater than 90% efficacies of three other already authorized COVID-19 vaccines. But Esper Kallas, a study investigator based at the University of São Paulo’s main campus who spoke at the press conference, notes that because definitions of a positive case have varied among trials, “There may not be an accurate comparability between the studies.” In the Brazil trial, the liberal definition of a case “put things to the most difficult test,” said Ricardo Palácios of Butantan, who served as the clinical director of the study. “It is like comparing someone who runs a kilometer on paved ground versus someone running 1 kilometer with obstacles.”

Science Magazine - January 12, 2021

View the full story here: https://www.sciencemag.org/news/2021/01/third-time-s-charm-brazil-scales-back-efficacy-claims-covid-19-vaccine-china