Prevalence of SARS-CoV-2 infection and dynamics of antibodies response among previously undiagnosed healthcare workers in a university hospital: A prospective cohort study

Background: Healthcare workers (HCWs) are a presumed high-risk population for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Identifying factors associated with seroprevalence can help establish better practices in healthcare settings. In this study, we evaluate prevalence of SARS-CoV-2 infection among previously undiagnosed HCWs and describe profiling of antibody responses against SARS-CoV-2, including neutralizing antibodies (NAbs). Methods: We analyzed a cohort of 386 HCWs in a university hospital in Egypt and 725 volunteers not affiliated to any healthcare facility (non-healthcare workers - NHCWs). Participants provided a nasopharyngeal swab and serum samples for SARS-CoV-2 nucleic acid and SARS-CoV-2-specific antibodies, respectively. HCWs who tested positive by either test were sequentially monitored. Results: At baseline, point prevalence of viral carriage was 11.4% in HCWs (n = 44/386) and 11.9% in NHCWs (86/725). The cumulative prevalence of SARS-CoV-2 infection among HCWs considering all studies was 25.6%, which was statistically lower than in NHCWs (41.0%). Prevalence was greatest among janitorial staff (45.9%) and the most affected departments were gastroenterology (31.1%), and emergency medicine (30.0%). Prior anosmia, fever or headache were associated with higher odds of positivity for SARS-CoV-2 infection. Regarding serial antibody measurements, RT-PCR-positive HCWs displayed IgG detection rates of 29.5%, 70% and 60% at visit 1, visit 2 and visit 3, respectively with slow decline of median IgG antibody titers, whereas, corresponding detection rates for total Ig antibodies were 50%, 90.3%, and 88.9%, respectively with increasing median titers. NAbs measured at each time point were positively correlated with total Ig levels, whereas IgG levels were positively correlated with NAbs at visit 1 and visit 3. Conclusion: Our results demonstrate lower cumulative prevalence of SARS-CoV-2 infection in HCWs than general population and suggest that asymptomatic HCWs exhibit considerable IgG and total Ig antibodies response as well as NAbs for up to 120 days, with positive correlation in between.