Seroprevalence of Covid-19 infection among healthcare workers: A study from a tertiary care hospital in the National Capital Region of India.

Background Seroprevalence studies on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can provide information on the target populations for vaccination. We aimed to evaluate the seroprevalence among healthcare workers (HCWs) at our tertiary care institution and to identify parameters that may affect it. Method We assessed seroprevalence of SARS-CoV-2 by the chemiluminescence immunoassay test among 3258 HCW in our hospital and evaluated as per gender, age, their previous Covid-19 diagnosis, role in hospital and type/risk of exposure. Results Of 3258 participants, 46.2% (95% CI 44.4%- 47.9%) were positive for SARS-CoV-2 IgG antibodies (i.e. IgG ≥15 AU/ml). Higher seroprevalence was seen in non-clinical HCWs (50.2%) than in clinical HCWs (41.4%, p=0.0001). Furthermore, people with a history of Covid-19 were found to have significantly higher antibody levels (p=0.0001). Among the HCWs, doctors and nurses had lower relative risk (RR) of acquiring Covid-19 infection (RR=0.82; 95% CI 0.76-0.89) compared to non-clinical HCWs. Conclusion Seroprevalence in HCWs at our hospital was 46.2%. Clinical HCWs had lower seroprevalence compared to non-clinical HCWs. Previous history of Covid-19 almost doubled the seropositivity, particularly in those with current infection.