SARS-CoV-2 surveillance strategy in essential workers of the Madrid City Council during the first epidemic wave in Spain, March-July 2020

Objectives: To study prevalence of infection in essential workers of Madrid City Council by occupation, related characteristics, use of protective devices, risk perception, and main concerns about COVID-19 during lockdown. Methods: A total of 30 231 workers were PCR tested for SARS-CoV-2 infection. Information was collected on COVID-19-related symptoms, risk factors, preventive equipment, and risk perception. The crude prevalence was calculated for infection, use of protective devices, perceived risk and main concerns. Additionally, adjusted prevalence and prevalence ratios (PR) were estimated for these variables using logistic regression models with age, gender, occupation, epidemiological week and laboratory as confounding factors. Results: Overall prevalence of infection was 3.2% (95% CI 3.0% to 3.4%), being higher among policemen (4.4%) and bus drivers (4.2%), but lower among emergency healthcare personnel, firefighters, food market workers and burial services (