Brazil’s Butantan Institute reported that Sinovac’s COVID-19 vaccine, CoronaVac, demonstrated an overall efficacy of only 50.38 percent in a phase 3 trial, putting it barely over the World Health Organization’s 50 percent efficacy threshold for approval.

The late-stage trial included 12,500 volunteers, all healthcare workers, across 16 sites in the country. The researchers previously said that the vaccine offered 78 percent efficacy against mild-to-severe infections, but they failed to include data from volunteers who contracted mild cases.

Brazil’s drug regulator, the National Health Surveillance Agency (ANVISA), said it is now reviewing the data for a possible emergency use approval. But vaccine experts have concerns about the data’s reliability because of varying efficacy rates reported by different countries and a lack of transparency by Sinovac.

Indonesian regulators said the CoronaVac vaccine showed 65.3 percent efficacy based on interim late-stage data and Indonesia authorized the vaccine for emergency use earlier this week, becoming the first country to do so since China authorized it last August ahead of phase 3 trial results (DID, Aug. 31, 2020). ― Jason Scott