Fig. 1

Timeline of sample collections and dominant circulating variants during the study period (A) and study flow diagram (B). This prospective study enrolled 111 CoronaVac-vaccinated individuals from May to June 202120 and 111 COVID-19 patients from three hospitals in central Thailand from July 2021 to December 202230,35. Plasma samples were collected on days 0, 14, and 28. RBD-ACE2 blocking antibody levels against the SARS-CoV-2 ancestral strain and 12 variants were assessed using multiplex sVNT30. Anti-spike antibody levels were measured using ECLIA, and anti-RBD IgG antibodies specific to the SARS-CoV-2 RBD of the Delta variant were determined by ELISA35.