Final efficacy analysis, interim safety analysis, and immunogenicity of a single dose of recombinant novel coronavirus vaccine (adenovirus type 5 vector) in adults 18 years and older: an international, multicentre, randomised, double-blinded, placebo-controlled phase 3 trial

Background:The Ad5-nCoV vaccine is a single-dose adenovirus type 5(Ad5)vectored vaccine expressing the SARS-CoV2 spike protein that was well-tolerated and immunogenic in phase 1 and 2 studies.In this study,we report results on the final efficacy and interim safety analyses of the phase 3 trial.Methods:This double-blind,randomised,international,placebo-controlled,endpoint-case driven,phase 3,clinical trial enrolled adults aged 18 years older at study centres in Argentina,Chile,Mexico,Pakistan,and Russia.Participants were eligible for the study if they had no unstable or severe underlying medical or psychiatric conditions;had no history of a laboratoryconfirmed SARS-CoV-2 infection;were not pregnant or breastfeeding;and had no previous receipt of an adenovirus-vectored,coronavirus,or SARS-CoV-2 vaccine.After informed consent was obtained,25 mL of whole blood was withdrawn from all eligible participants who were randomised in a 1:1 ratio to receive a single intramuscular dose of 0·5 mL placebo or a 0·5 mL dose of 5×1010 viral particle(vp)/mL Ad5-nCoV vaccine;study staff and participants were blinded to treatment allocation.All participants were contacted weekly by email,telephone,or text message to self-report any symptoms of COVID-19 illness,and laboratory testing for SARS-CoV-2 was done for all participants with any symptoms.The primary efficacy objective evaluated Ad5-nCoV in preventing symptomatic,PCR-confirmed COVID-19 infection occurring at least 28 days after vaccination in all participants who were at least 28 days postvaccination on Jan 15,2021.The primary safety objective evaluated the incidence of any serious adverse events or medically attended adverse events postvaccination in all participants who received a study injection.This trial is closed for enrolment and is registered with ClinicalTrials.gov(NCT04526990).