In the phase 2 trial of the Ad5-nCoV vaccine, the low-dose and high-dose groups achieved 97% and 96% seroconversion of specific antibodies on day 28, respectively, while the placebo group experienced no antibody increase. The vaccines induced significant specific IFNγ-ELISpot responses, although T cell responses were negative in 99% of participants. Solicited adverse drug reactions (ADRs) were reported by 96 of 129 participants in the low-dose group (1 severe) and 183 of 253 in the high-dose group (24 severe), but no serious ADRs were documented. Overall, the vaccine candidate was found to be safe at low doses and capable of eliciting a significant immune response after a single injection.