This is a randomized, single-blind, placebo-controlled clinical trial to evaluate the efficacy and safety of SA58 nasal spray in close contact with COVID-19 people.

This study is a randomized, single-blind, placebo-controlled clinical trial in close contacts to COVID-19. The investigational drug was manufactured by Sinovac Life Sciences Co. , Ltd.The purpose of this study is to estimate the efficacy and safety of SA58 nasal spray in close contacts to COVID-19. A total of 2900 subjects were planned to be enrolled,including 2300 subjects who were non-continuous exposed to COVID-19 in group A,600 subjects who were continuous exposed to COVID-19 in group B. All subjects started medication on the day of enrollment. During the medication period, the subjects were given nasal spray once every 3 hours,about 5-6 times a day.

Inclusion Criteria:

• Subjects aged 18 years and above on the day of enrollment;
• Had recent contact with an infected person, and the time of PCR sampling from a positive infected person, or the time of first contact with a positive infected person should not exceed 72 hours;
• The subjects can understand and voluntarily sign the informed consent form;

Exclusion Criteria:

• Previous history of severe allergy or sensitivity to inhalation allergens;
• Women are breastfeeding, pregnant, or planning to become pregnant during the study period;
• Participated in clinical trials of SARS-CoV-2 neutralizing antibody injections within 180 days prior to screening or clinical trials of other drugs within 4 weeks prior to screening;
• Subjects unable to cooperate with nasal spray inhalation;
• Body temperature at baseline (Day 0)>37.0℃;
• Had a severe neurological disorder (epilepsy, convulsions or convulsions) or psychosis, and have a family history of psychosis;
• The researchers determined that the subjects had a serious chronic medical condition that could interfere with the conduct or completion of the study;
• According to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.