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Background: The longitudinal study was conducted over the initial 2 years of the COVID-19 pandemic, spanning from June 2020 to December 2022, in healthcare workers (HCWs) of the Thomayer University Hospital. A total of 3892 blood samples were collected and analyzed for total nucleocapsid (N) antibodies. The aim of the study was to evaluate the dynamics of N antibodies, their relationship to the PCR test, spike (S) antibodies, interferon-gamma, and prediction of reinfection with SARS-CoV-2., Methods: Blood collections were performed in three rounds, along with questionnaires addressing clinical symptoms of past infection, PCR testing, and vaccination. Antibody measurements included total N antibodies (Roche Diagnostics) and postvaccination S antibodies (Euroimmun). Cellular immunity was tested by interferon-gamma release assay (Euroimmun)., Results: At the end of the study, 35.9% of HCWs were positive for N antibodies, and 39.5% of HCWs had either known PCR positivity or N antibodies or both. Ten percent of participants had no knowledge of a COVID-19 infection and 35% of positive individuals exhibited no symptoms. The values of positive antibodies decrease over a period of 6 months to 1 year, depending on the initial value, and their dynamics are highly variable. The study also demonstrated that the highest levels of spike antibodies and interferon-gamma occur during so-called hybrid immunity., Conclusion: Nucleocapsid antibodies proved valuable in monitoring SARS-CoV-2 infection dynamics, and they may detect cases of SARS-CoV-2 infection missed by PCR tests. The study identified distinct patterns in antibody dynamics and protection of hybrid immunity during reinfection., (© 2025 The Author(s). Journal of Clinical Laboratory Analysis published by Wiley Periodicals LLC.)

Objectives: To map the prevalence of SARS-CoV-2 antibodies in the staff of the Thomayer University Hospital in Prague following the first wave of COVID-19. The main reason was the large number of COVID-19 patients admitted to the Thomayer University Hospital with confirmed SARS-CoV-2 infection., Material and Methods: A volunteer study based on a questionnaire survey and determination of total antibodies (ECLIA, Roche) and individual classes of immunoglobulins (ELISA IgG and IgA, Euroimmun)., Results: The study involved 808 employees, 2/3 of whom were from clinical departments. Fifteen participants, predominantly nurses (n = 12), tested ECLIA positive for antibodies against SARS-CoV-2 and ELISA positive or borderline positive for IgG antibodies. Positive or borderline IgA antibodies were recorded in 12 subjects. Most of the positive study participants (n = 13) contracted the SARS-CoV-2 virus at the workplace after repeated contact with positive patients. Most subjects infected (n = 12) had a more severe course but did not require hospitalization. We detected only one asymptomatic antibody-positive person., Conclusions: After the first wave of COVID-19, SARS-CoV-2 antibodies were only demonstrated in 1.9% of the Thomayer University Hospital employees tested. In clinical departments, the positivity rate was 2.3%, and in non-clinical departments, it was only 0.5%. The low prevalence of antibodies points to the low number of infected hospital staff and a very good level of compliance with all public health and epidemiological measures.