Serological prevalence of SARS-CoV-2 infection and associated factors in health care workers in a "non-COVID" hospital in Mexico City

Background: Mexico is one of the countries with the highest number of deaths from the COVID-19 pandemic. However, the number of confirmed cases and RT-PCR tests per million population are lower than for other countries, which leads to uncertainty about the actual extent of the pandemic. In Mexico City, health care workers represent an important fraction of individuals with SARS-CoV-2 infection. This work aims to estimate the frequency of antibodies to SARS-CoV-2 in health care workers at a non-COVID hospital, as well as identify factors associated with SARS-CoV-2 infection in this population. Methods: We conducted a serological survey in a large non-COVID teaching hospital in Mexico City. The study population included all the personnel that works, in any capacity, in the hospital. From this population we selected a representative sample of 300 individuals. Blood samples were collected and questionnaires were applied between August 10th and September 9th, 2020. Results: ELISA results indicate a serological prevalence to SARS-CoV-2 infection of 13.0%. Working in the janitorial and security groups, having an educational level below a university degree, and living with larger numbers of people, were also identified as sociodemographic factors that increase the risk of having SARS-CoV-2 infection. Conclusions: Even though the rate from the official number of confirmed cases in Mexico City is substantially smaller than the seropositive rate identified in this work, even in health care workers there is still a majority of individuals that are seronegative, and thus the risk of continued epidemic waves and mortality remains high.