Is Covid-19 seroprevalence different in health care workers as per their risk of exposure? A study from a tertiary care hospital in National Capital Region of India

Abstract Background: SARS CoV 2 infection has severely ravaged health systems, economic and social progress globally in 2020. Seroprevalence studies can provide relevant information on the target populations for vaccination. They are relevant not only in the community, but also for critical population subgroups such as nursing homes or health care facilities. They will assist in strategizing the vaccination policy especially since there is limited availability of the vaccine and vaccine hesitancy Objective To evaluate the seroprevalence in Health Care Workers (HCW) at our hospital and to identify parameters which may affect it. Methodology: The Baseline profiling and seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS CoV 2) was assessed among 3258 healthcare workers (HCWs) of Medanta-The Medicity, Gurugram, Haryana, India, as a part of an ongoing cohort study.The fully automated LIAISON SARS CoV 2 S1/S2 IgG test using the chemiluminescence immunoassay (CLIA) for the quantitative determination of anti S1 and anti S2 specific IgG antibodies to SARS CoV 2 was used to test serum samples collected before the receipt of the vaccine. Seroprevalence was evaluated as per gender, age, association with previous Covid-19 diagnosis, use of supplements, and role in the hospital and type of exposure. Results: Of the 3258 participants tested for IgG serology (S1 and S2 proteins) 46.2% (CI 44.4 to 47.9%) were positive (i.e. had an antibody titre more than 15 Au/ml). Higher seroprevalence was seen in the others ie non clinical health care workers (including management, research personnel, pharmacists, technicians, general duty staff, housekeeping, security, food and beverage, and facility maintenance teams) (50.2 Au/ml) than that in clinical HCW (ie doctors and nurses)where it was significantly lower (41.4 Au/ml, p= 0.0001). Also, people with history of Covid-19 were found to have significantly higher antibody levels (p = 0.0001). Amongst the healthcare workers, doctors and nurses had higher relative risk of acquiring Covid-19 infection (RR = 1.21; 95% C.I.: 1.12 to 1.31). Conclusion: Seroprevalence in healthcare workers at our hospital is high at 46.2%. It is higher in non-clinical HCW than in clinical HCW . The risk of acquiring Covid 19 infection was higher in clinical HCW and thus, this subgroup may benefit most from vaccination. History of Covid 19 may provide double the protection, in particular in those who had it recently. Keywords: SARS CoV 2, vaccination, herd immunity, healthcare workers, seroprevalence