Study vaccines
The manufacturing process and facilities for CoronaVac have been described previously (CoronaVac used in this trial was packed in prefilled syringes and stored at 2-8°C. It was administered intramuscularly into the lateral deltoid muscle of upper arm, at a dose of 600SU/0.5ml (3μg antigen). In this trial, the schedule of vaccination was two doses on Day 0,28. Seven lots of CoronaVac from three workshops, on a commercial scale, were used in this trial. Workshop 1 provided one lot of CoronaVac (lot number: D202104004), and workshop 2 and 3 each provided three consecutive lots (lot number of D202105014, U202106002 and A202106042 for workshop 2, and A202105034, A202106035 and A202106036 for workshop 3, respectively). All lots of CoronaVac had been approved by the National Institutes for Food and Drug Control (NIFDC) of China.