[Anti-SARS-CoV-2 seroprevalence in administrative staff of the Mexican Institute for Social Security].

Background: Asymptomatic subjects, the lack of diagnostic tests and, in countries like Mexico, the epidemiological surveillance method does not allow to establish the real number of infections in the COVID-19 pandemic. Frontline health personnel, as well as other groups related to priority activities are considered of high risk. We included administrative workers in contact with health personnel in the hospital units of the Mexican Institute for Social Security (IMSS, according to its initials in Spanish). Objective: To identify the seroprevalence of antibodies to SARS-CoV-2 in IMSS' administrative staff who does not treat patients. Material and methods: 76 volunteer participating individuals were incluided; IgG antibodies against the SARS-CoV-2 nucleoprotein were measured. A questionnaire was administered to the participants in order to identify possible risk factors. Results: 76 participants were included (39 men, 51.7%), with a median age of 42 years. 29 out of 76 subjects (38.2%), whose median age was 38 years (range 18-69 years); 15 men (51.7%), and 14 women (48.3%). A higher percentage of positive subjects under 45 years of age (n = 20, 84.2%) was observed than those aged 45 or over (n = 9, 25%), with an OR of 3 (95% CI 1.13-7.96, p = 0.03). No statistically significant difference was found regarding the type of comorbidity. Conclusions: The prevalence identified shows an important circulation of the virus in the administrative staff.