The Lancet presented the interim results of a double-blind, randomised, controlled trial of CoronaVac versus placebo in Turkey. Adults aged 18–59 years who were seronegative and RT-PCR-negative for SARS-CoV-2 infection received two doses of CoronaVac or placebo with a 14-day interval between doses.
The primary, per protocol analysis of vaccine efficacy included 10,029 participants who received two doses of vaccine or placebo. The primary outcome was the incidence rate of PCR-confirmed symptomatic COVID-19 occurring later than 14 days after the second dose, of which 41 cases were reported. Nine of these cases were in the CoronaVac group and 32 were in the placebo group giving a vaccine efficacy of 83·5%. Six participants were hospitalised with COVID-19, all in the placebo group.