Evaluation of IgG Antibody Responseto Severe Acute Respiratory Syndrome Coronavirus-2 in Healthcare Workers in aTertiary Care Centre, Chennai, India

Globally, the Coronavirus Disease-2019 (COVID-19) pandemic poses a high risk for Healthcare Workers (HCWs) who are among the population that is most vulnerable of being infected with Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2). With a prevailing pandemic such as COVID-19, it becomes important to understand the presence and persistence of antibodies in the serum of HCW, testing positive for COVID-19 on Reverse transcriptase Polymerase Chain Reaction (RT-PCR). An understanding of the prevalence of IgG antibodies against COVID-19 and the duration for which they are present in the serum will help in predicting the immune response of individuals against the disease. Aim: To study the prevalence of COVID-19 IgG antibodies in laboratory confirmed COVID-19 RT-PCR positive symptomatic, asymptomatic and RT-PCR negative subjects. Materials and Methods: The present longitudinal study was conducted from April to December 2020 with a sample size of 90 participants based on a pilot study. Blood sample was collected and serum was separated. Enzyme Linked Immunosorbent Assay (ELISA) was done to detect the presence of COVID-19 IgG antibody in serum. Chi-square test and Pearson correlation were used to find out the statistical significance of COVID-19 IgG antibodies in COVID-19 positive and negative HCWs and the relationship between Cycle threshold values (Ct) and antibody levels, respectively. Results: Fever with sore throat was the most common (33%) symptom. Chi-square test done to compare IgG among RT-PCR positive and negative subjects showed p-value of <0.0001 which was significant. However, statistical significance was not found (p-value 0.9973) with respect to COVID-19 IgG antibodies in RT-PCR positive COVID-19 asymptomatic and symptomatic subjects. Mean antibody index in symptomatic and asymptomatic was 3.7743±1.9834 and 3.571±1.7961, respectively. Average number of days, the antibodies persisted was 25 days-266 days. Conclusion: The prevalence of COVID-19 antibodies among RT-PCR positive symptomatic, asymptomatic and RT-PCR negative subjects was 87.8%, 66.7% and 26.7%, respectively. The maximum number of days antibodies persisted was 266days. Further studies will elucidate whether these antibodies prevent re-infection.