Seroprevalence against SARS-CoV-2 in health workers: evaluation 6 months after the complete scheme and reinfections

Abstract Background One of the priority lines for the containment of the SARS-CoV-2 virus pandemic is the vaccination programs for health personnel. However, with the emergence of highly contagious strains such as the Omicron variant, it is necessary to know the serological status of health personnel to make decisions for the application of reinforcements. Objectives To determine the seroprevalence against SARS-CoV-2 in health workers in a Mexican hospital, after six months of the administration of the Pfizer BioNTech vaccine and the association between comorbidities, response to the vaccine and reinfections. Methods Antibodies against SARS-CoV-2 were determined by ELISA assays in 262 employees of the Hospital Juárez de México with and without a history of COVID-19. A beta regression analysis was performed to study the associated comorbidities and their relationship with the levels of antibodies against SARS-CoV-2. Finally, epidemiological follow-up was carried out to detect reinfections in this population. Results A significant difference in SARS-CoV-2 seroprevalence was observed in workers with a history of COVID-19 prior to vaccination, compared to those without a history of the disease. Beta regression showed that workers with a history of COVID-19 have greater protection, compared to those without a history of the infection. Neutralizing antibodies were found to be decreased in alcoholic and diabetic subjects. Eight cases with omicron reinfections were identified, and gender and obesity are associated with the presence of reinfections. Conclusion The response to the vaccine was influenced by the history of SARS-CoV-2 infection and associated comorbidities. The above highlights the importance of prioritizing this segment of the population for reinforcements in periods of less than one year to guarantee their effectiveness against new variants.