At a press conference Tuesday, Sao Paulo state officials and researchers from Butantan Institute explained that they split the cases in six categories: asymptomatic, very mild, mild, two levels of moderate, and severe -- the first two not requiring medical assistance.
The 78% was calculated considering the mild, moderate and severe cases, officials said. When very mild cases among the 13,000 volunteers are included, the figure is 50.4% -- 167 infected in the placebo arm, and 85 in the vaccine arm.