Results
Since November 27, 2022, a total of 657 individuals were screened in the designated quarantine hotels. There were 101 individuals excluded according to the inclusion and exclusion criteria. The remaining 556 individuals were assigned into either A8G6 treatment group or blank-controlled group based on their preference during signing of consent form. For participants who indicated “no preference” in study group assignment, they were randomly assigned to A8G6 treatment group or the blank control group. Ten participants in the treatment group and 33 participants in the control group were excluded due to consent withdrawal or loss to follow up (Fig.  Screening and follow-up of participants. Healthy adults aged between 18 to 65 years who had a close contact with index cases within 72 h were enrolled into this study from 6 quarantine sites in Chongqing between Nov 27, 2022 and Dec 5, 2022. During this trial, the outbreak of COVID-19 was dominant by BA.5.2 (Omicron subvariant)The final number of subjects completing the trial was 173 subjects in the A8G6 treatment group and 340 subjects in the control group. In the treatment group, 4 participants started to self-administrated A8G6 at the same day after exposure (Day 0); 73 participants used the nasal spray at the first day after exposure (Day 1); 49 participants at the second days after exposure (Day 2); 35 participants at the third day after exposure (Day 3) and 12 participants at more than 4 days after exposure (Day≥4). Among all participants in the full analysis set, median age was 36.0 (interquartile range, IQR: 26.0–48.0) years; there was a comparable sex ratio between the A8G6 group (55.5% for male and 44.5% for female) and the control group (58.2% for male and 41.8% for female); median BMI was 22.9 (IQR: 20.8–25.4); 18 (10.4%) participants in the treatment group have comorbidities, while 44 (12.9%) participants in the control group have comorbidities. 98.4% participants received different doses of COVID-19 vaccines (Table Demographic and clinical characteristics of the cohortShown are all participants who were recruited in our trail and received A8G6 treatment or no treatment. 