Effectiveness Evaluation of the Sinopharm Vaccine in the Dondo District in Mozambique

Inclusion Criteria: 1. They resided in the study area at the time of mass immunization with the Sinopharm vaccine; and 2. They are at least 18 years of age during first round of mass vaccination. 3. Their onset of symptoms was \<10 days prior to testing. 4. For each selected PCR test-positive case, we will select up to 3 test-negative controls from generally eligible subjects, matched to each case by age on the date of testing, sex, and calendar date of testing + 3 days. Exclusion Criteria: 1. We will exclude subjects for selection as controls if they have had a positive test result within the following 21 days 2. Any Participant not matching the inclusion criteria mentioned above.