Non-COVID Health Care Workers with Positive Antibody Responses: Are We Heading Towards Herd Immunity?

Background: Antibody testing against SARS-CoV-2 complimentary to RT-PCR could be an effective method for its detection. Development of immunity against COVID-19 in context of reinfection and herd immunity still remains debatable and needs further elucidation. The present study was conducted to investigate the immunity status against SARS-CoV-2 in terms of IgG antibody positivity in health care workers at a tertiary care center. Methodology: This single center study was conducted at a tertiary care center, that involved 1039 healthcare workers and other staff members. The testing of all subjects was performed using ELIFAST (SARS-CoV-2 IgG ELISA) kits. The sample population was then segregated into RT-PCR positive and negative/status unknown groups. Groups were further segregated on the basis of IgG positivity status and the sensitivity and specificity was also calculated. Results: Among the 1039 enrolled subjects, 179 (17.23%) were RT-PCR positive for SARS-CoV-2 positive and remaining were either RT-PCR negative or status unknown cases. Among 179 COVID-19 recovered subjects, 19 (10.61%) were negative for IgG, whereas 160 (89.39%) came out IgG positive. Out of 860 (82.77%) RT-PCR Negative/Status unknown, 248 (28.84%) came out IgG positive and the remaining 612 (71.16%) were negative for IgG. The overall sensitivity and specificity were 89.39 and 71.16, respectively. Conclusion: A combined approach of testing for COVID-19 using RT-PCR and rapid antibody assays could be more beneficial. Serological studies project a higher antibody response in population that compel us to think about plausibility of herd immunity. However, variability in serological response could be affected by several factors and the underlying complex immune process of COVID-19 is yet to be fully understood.