Seroprevalence of SARS-CoV-2 in Asymptomatic Frontline COVID-19 HCWs

Coronaviruses (CoVs) are enveloped, single positive-strand RNA viruses belonging to the large
subfamily Coronavirinae, which can infect mammals and several other animals.The continued
spread of coronavirus disease 2019 (COVID-19) has prompted widespread concern around the
world, and the World Health Organization (WHO), on 11 March 2020, declared COVID-19 a
pandemic. Studies on severe acute respiratory syndrome (SARS) and Middle East respiratory
syndrome (MERS) showed that virus-specific antibodies were detectable in 80-100% of patients
at 2 weeks after symptom onset. Currently, the antibody responses against SARS-CoV-2 remain
poorly understood and the clinical utility of serological testing is unclear. Little is known
about the kinetics, tissue distribution, cross-reactivity and neutralization antibody
response in COVID-19 patients. Asymptomatic cases are common but to date there are scarce
epidemiological surveys that provide a clear percentage of asymptomatic cases.

A large number of healthcare workers have been infected with the virus worldwide, presenting
with severe symptoms to no symptoms at all, in which case being diagnosed on contact tracing
only. The seropositivity rate in previously undiagnosed healthcare workers has been reported
in different regions of the world. In a combined study of three hospitals of Turkey, the
seropositivity rate of the previously undiagnosed HCWs was 2.7%. A study done in China
revealed 17.5 % seropositivity rate.

This study will aim to comprehensively review the current knowledge on the immunological
changes observed in various healthcare workers in this part of the world, who remained
asymptomatic while working in high exposure areas of COVID-19 infection.