Morocco 2020–2023: Three-Year Serosurvey of Anti-SARS-CoV-2 Antibodies in Outpatients & Health Care Workers

Background: Seroprevalence studies are vital for understanding SARS-CoV-2 spread and vac-cination impact. In Morocco, data on antibody prevalence among outpatients and healthcare workers (HCWs) were limited before this study. Objective: The study aims to evaluate anti-SARS-CoV-2 antibody prevalence among outpatients and HCWs in Morocco over three years, before and after the national COVID-19 vaccination campaign. Methodology: Three cross-sectional surveys were conducted from December 2020 to July 2023. Blood samples from randomly selected outpatients and HCWs were tested for anti-SARS-CoV-2 antibodies using the Architect platform. Demographic and occupational data were collected. Results: The surveys included 231,283 participants (227,569 conclusive results). The first survey (40,925 outpatients) showed a seroprevalence of 0.12%. The second survey (110,699 participants: 91,977 outpatients, 18,722 HCWs) reported 24.7% seroprevalence and the third survey (79,659 participants: 72,929 outpatients, 6,730 HCWs) indicated a seroprevalence of 96.8%. Multivariate analysis of the third survey showed vaccination strongly correlated with antibody prevalence, with odds ratios of 65.5 (one dose), 416.9 (two doses), and 890.9 (three doses) compared to unvaccinated individuals. Conclusion: Anti-SARS-CoV-2 antibody prevalence in Morocco increased significantly from 0.12% to 96.8% over three years, driven by widespread infection and the effective national vaccination program.