Background: Coronavirus Disease 2019 (covid-19) is a highly contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). People who are infected with SARS-CoV-2 or are vaccinated with covid-19 vaccines are supposed to develop immunoglobulins and these immune responses in human body will determine the efficacy of the vaccines as well as help to discover new therapeutic options. Methods: A cross-sectional study conducted between April to June, 2021, assessing serum antibody titer from participants who had taken the first dose of covishieldTM vaccine (naïve as well as prior covid-19 infected individuals). Antibody testing was carried out with Roche Elecsys Anti-SARS-CoV-2 S electrochemiluminescence immunoassay on Roche Cobas e 601 module. Twenty-eight of these participants had follow up repeat antibody test after second dose of vaccine. Results: A total of 122 participants with the first dose of CovishieldTM vaccine were all tested seropositive, antibody titer ranging from minimum of 2.95 U/mL to maximum 2500 U/mL. Average antibody titer was 308.9 U/mL for naive cohort and 1604 U/mL for prior covid-19 infection. In twenty-eight participants who had antibody titer measured after 1 month of second dose, average titer was 1459.7 U/mL for naïve cohort and 1803.4 U/mL for prior covid-19 infected individuals, which was statistically significant compared to antibody response after the first dose. Conclusions: Antibody responses against SARS-CoV-2 following immunization was 100%, with significant development after second dose in naïve population while robust immune response was present after first dose in prior SARS-CoV-2 infected individuals.

Background: Severe Acute Respiratory Syndrome Corona Virus 2019, a novel coronavirus first reported from China in 2019, is the causative agent of pandemic corona virus disease 2019. Antibody response and its dynamics may provide information about natural immunity conferred upon by corona virus disease 2019. Methods: A health-center-based follow up study of confirmed Severe Acute Respiratory Syndrome Corona Virus-2 infected patients was conducted from December 2020 to June 2021. Patients were followed up to period of 28 weeks during the study. An electrochemiluminescence immunoassay was used to test antibodies elicited by Severe Acute Respiratory Syndrome Corona Virus-2. Socio-demographic and clinical information was collected from each patient.Results: A total of 40 patients (18 males and 22 females) were enrolled in the study, with 90 % seropositivity of SARS-CoV-2 antibody. Antibody level was tracked up to 28 weeks following the infection, and persistence was observed till the end. Antibody level peaked on the 3rd to 4th month, after symptom onset. The male population was found to have higher antibody levels compared to females. Age-wise trend analysis showed lower antibody levels in the younger people (15-30 years) than those older (31-60 years).Conclusions: We demonstrated that Severe Acute Respiratory Syndrome Corona Virus-2 specific antibodies in corona virus disease 2019 patients persist for at least 28 weeks, peaking at 13 to 20 weeks. Statistically, there was no correlation of antibody levels with the age and sex of individuals. Further study on a larger population is needed for determining long-term immunity.Keywords: Antibody; kinetics; SARS- CoV-2.

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