Randomisation and study populations
The investigational vaccine, Ad5-nCoV, and the placebo were provided by NPO Petrovax Pharm LLC (Moscow, Russia). Both vaccine and placebo were developed by CanSino Biologics Inc. (Tianjin, China) and the Beijing Institute of Biotechnology (Beijing, China). The vaccine was administered with the optimal dose of 5 × 10Eligible participants were randomly allocated to the Ad5-nCoV group or the Placebo group, in a 3:1 ratio, by an independent statistician using a validated system including a pseudorandom number generator with a seed value; allocation used block randomisation and stratification by study site. Neither the investigators nor participants were aware of the group assignment. Investigators were trained to use the centralised interactive web response system that was used for randomisation. Randomisation codes were kept by authorised personnel from the responsible contracted organisation.The Safety Analysis Set included all randomised participants who received a dose of the vaccine and was used to provide the disposition of study participants. Results for immunogenicity analyses are presented for the full analysis set (