Antibody Response Profile in COVID-19 Infection in Healthcare Workers: Insights from a Study at a Reference Laboratory

ABSTRACT

Introduction: The Coronavirus Disease 2019 (COVID-19) pandemic has imposed an unprecedented burden on our healthcare system. Serological testing for Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) antibodies serves as an useful marker for determining an infection by the virus in the recent past and the immune response. The immune response, including the humoral response to the infection is one of them and the knowledge in this area is still evolving. Virus specific antibodies are expected to help in eliminating the virus and to provide protective immunity against reinfection. Aim: To serially monitor the total antibody response to SARSCoV-2 in order to gain better insight into the duration of antibody persistence. Materials and Methods: This prospective observational study was conducted in 66 Healthcare Workers (HCW) with a history of Reverse Transcription- Polymerase Chain Reaction (RT-PCR) proven COVID-19 infection. The study was conducted between May 2020 to April 2021 at the Suburban diagnostics Central Processing Laboratory, Mumbai, Maharashtra, India. Serum samples were serially examined for the presence of total antibodies against the Nucleocapsid (N) protein of SARS-CoV-2 upto 180 days postinfection. A further follow-up examination was done at 360 days. A qualitative Electrochemiluminescence Immunoassay (ECLIA) assay was used for assessment of the antibody response. The chi-square or Fisher-exact test was used to compare categorical variables and the Mann-Whitney U test, Kruskal Wallis test and student t-test were used to compare continuous variables across groups. For assessing relationship between variables, the Pearson test or linear regression were used as appropriate. Results: Out of 66 healthcare workers, 32 were male (48.5%) and 34 were females (51.5%) with the median age of 29.5 years. Out of 66 cases, 62 (94%) cases developed antibodies against SARS-CoV-2 at different time intervals, 48 cases during the 14-30 day interval, 10 cases during the 31-60 day interval, three cases during the 61-90 day interval and one case during the 90-120 days interval. Thirty one out of 35 (88%) cases that could be followed-up at 360 days showed persistence of antibodies. No patient reported symptoms which would warrant a repeat RT-PCR test. Conclusion: This study showed that the antibody response to SARS-CoV-2 virus was sustained for 12 months postinfection in most cases. The absence of fresh infection in these cases during the study period suggests that the antibodies might protect against reinfection with the virus. So, it may be safe to defer vaccination in postinfection cases by 6-9 months thereby saving precious resources.