Inclusion Criteria:

1. ≥18 years old at the signing of informed consent.

2. Household contacts of individual with symptomatic COVID-19. Symptomatic COVID-19
cases (index case) to be identified as those symptomatic and recently tested (rapid
antigen test or RT-PCR) positive for SARS-CoV-2 and must fulfill the following
criteria 1) collection of the first positive SARS-CoV-2 test sample less than 48
hours before randomization, 2) have at least one symptom attributable to COVID-19.

3. RT-PCR test negative (with nasopharyngeal [NP] swab samples) OR rapid antigen test
negative at the time of screening and without any suspicious COVID-19 symptoms
within 2 weeks before randomization.

4. Subject expects to be living in the same household with the symptomatic COVID-19
cases during the whole study period.

5. Willing and able to comply with study visits and study-related
procedures/assessments.

6. Provide informed consent signed by study subject or legally acceptable
representative.

Exclusion Criteria:

1. Subject with a history of SARS-CoV-2 vaccinations within 6 months before
randomization.

2. Subject with a history of SARS-CoV-2 infection within 6 months before randomization.

3. Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >3×Upper Limit of
Normal (ULN) ,or total bilirubin (TBIL) >2×ULN.

4. Creatinine clearance (Ccr, calculated by Cockcroft-Gault equation)<60 ml/min or
Creatinine >1.2×ULN.

5. With any serious infection requiring systemic anti-infective therapy within 14 days
before randomization.

6. Allergic to the investigational agent or any components of the formulation.

7. Pregnant or breast-feeding women.

8. Previous administration of any antiretroviral drugs (e.g., antiretroviral drugs for
HIV, HBV, or HCV) within 7 days before randomization.

9. Women of childbearing potential who are unwilling to practice highly effective
contraception during the study, and for at least 6 months after the study; Sexually
active men who are unwilling to use medically acceptable birth control during the
study period.

10. Have other conditions not suitable for inclusion as judged by the investigator.