Procedures
FINLAY-FR-2 was administered via intramuscular injection, 28 days apart. FINLAY-FR-1A was used as a third dose in cohort 2 on day 56. Vaccine composition is presented in the eMethods in QuantiVac ELISA (enzyme-linked immunosorbent assay IgG) kit (Euroimmun, Germany) was used to determine the titration of anti-S1 IgG (including RBD) antibodies. To evaluate vaccine immunogenicity, a representative sample of participants (30% of the total) was selected from randomly selected cities on days 0 and 56 in cohort 1 (n = 5905) and days 0 and 84 in cohort 2 (n = 1975). Microneutralization assayParticipants with suspected COVID-19 (based on symptoms) were tested using a 1-step RT-PCR kit (Pishtaz Teb Diagnostics), with the findings confirmed with the 2019-nCoV Nucleic Acid Diagnostic Kit (Sansure Biotech). Participants with RT-PCR–positive testing with an N gene cycle threshold value less than 25 underwent an S gene sequence analysis.