Participants
During November COVID-19 wave in Chongqing, China, when patients had been diagnosed as COVID-19 with the positive RT-PCR test for SARS-CoV-2 (index cases), their close contacts were immediately transferred to the designated quarantine sites. At 6 quarantine sites in Chongqing, healthy adults aged between 18 to 65 years who had a close contact with index cases within 72 hours were enrolled into this study. The maximum time interval between exposure to treatment was ≤72 h. All vaccination status is eligible for inclusion. Exclusion criteria included positive RT-PCR at baseline, nasal discomfort, the use of other COVID-19 antibody drugs and drug-drug interference with participants’ regular medication (additional details about eligibility criteria were described in the appendix).All study participants were capable of self-administrating the intranasal spray, recording and recalling clinical signs. All participants were provided and voluntarily signed written informed consent before the study.