Doctors had the lowest titers. ECLIA-based Cobas e411 analyzer. Univariate and multivariate regression were used in statistical analysis. Results: Our results show that 95.1% and 99.5% of the vaccinated individuals have developed antispike protein Diethyl aminoethyl hexanoate citrate antibodies after the first and second doses, respectively. Previous COVID-19 infection was significantly correlated with antibody production, and age was negatively correlated. No difference was reported for sex, occupation, and diabetes. Conclusion: Our interim analysis report is coherent with the available literature and research regarding the high efficacy of the COVID-19 vaccine as far as seroconversion is concerned. Keywords: ChAdOx1 vaccine, healthcare worker, regression, SARS-CoV-2, seroconversion Introduction Coronavirus disease (COVID-19) is a highly infectious disease caused by type 2 SARS coronavirus. The majority of infected people experience mild-to-moderate respiratory illness and do not require hospitalization.[1] People developing serious illnesses are either old or people with comorbidities.[2] SARS-CoV-2 is transmitted mainly through aerosol and droplets.[3] COVID-19 was declared as a Public Health Emergency of International Concern on January 30, 2020. Since then, it has spread to all the World Health Organization (WHO) member states.[4] There have been nearly 175 million confirmed cases of COVID-19, including 3.7 million deaths. As of June 9, 2021, a total of 2,156,550,767 vaccine doses have been administered.[5] Recognizing the need for vaccines, WHO published a road map for vaccine development as early as March 6 with SOP for clinical trials.[6] Till June 8, 2021, there are 102 vaccines in the clinical development phase, and a further 185 vaccines are in the preclinical phases. Out of the 102 vaccines in clinical trials, 31 are protein subunits and 16 each of viral vector-borne (nonreplicating), RNA, and inactivated vaccines.[7] The majority of vaccines developed so far have been assessed by their ability to elicit antibody responses, and the generation of neutralizing antibodies has been the primary goal of vaccination.[8] Antigen-specific antibodies have been formally demonstrated as conferring Diethyl aminoethyl hexanoate citrate vaccine-induced protection against many diseases.[9] Current vaccines predominantly mediate protection through the induction of highly specific IgG serum antibodies. In practice, to evaluate vaccine-mediated protection, estimation of antibody titer is the only feasible and available option as in rubella.[8] In India, Covaxin (BBV152) and Covishield (ChAdOx1) were given emergency approval for restricted use in 2021.[10] Covishield (ChAdOx1) is Diethyl aminoethyl hexanoate citrate a vector (adenovirus)-based recombinant nCoV-19 coronavirus vaccine with spike protein antigen.[11] It has been demonstrated in phase 1/2/3 clinical trials that there is a good antibody response after a single dose of the Covishield vaccine and that is neutralizing in nature, which further escalates after the second dose. [12] India started its vaccination drive on January 16, 2021, with the healthcare workers being the initial beneficiaries. The phase 3 trial data for Covishield shows 70% efficacy 14 days after the second dose of the vaccine.[13] The Spike protein (S glycoprotein) of coronaviruses (CoVs), which helps the virus fuse with the host cell membranes, is the primary immunogenic target for virus neutralization and vaccine design.[14,15] Also, most serological assays detect the neutralizing antibodies against the spike CASP3 (S) protein.[16] Serological testing provides direct evidence of population immunity, and quality serological surveys help in crucial insights into the communitys immunological profile. They identify immunity gaps to prioritize additional vaccination interventions in these communities.[17,18] Also, these serological surveys tend to be more accurate than indirect estimations based on extrapolation of coverage and incidence data in this COVID-19 scenario with limited testing capabilities.[19] As antigen-specific antibodies are symbols of vaccine-induced immunity, estimation of serum antibodies will provide important information regarding vaccine efficacy in seroconversion and the overall communitys immunization status. As there is limited study on antibody prevalence to SARS-CoV-2 post vaccination, our study aimed to estimate the prevalence of anti-SARS-CoV-2 antibodies and identify the predictors of antibody titers among vaccinated healthcare workers in VIMSAR, Burla. As vaccine hesitancy is a concern among the population and healthcare providers, the knowledge gained from the study will improve vaccine confidence among the primary care physicians to advocate for COVID vaccination, which will lead to increased coverage and herd immunity. Methods A repeated cross-sectional study was conducted in Veer Surendra Sai Institute of Medical Science and Research, Burla, Sambalpur, Diethyl aminoethyl hexanoate citrate in the state of Odisha among healthcare workers, which include doctors, nurses, students, and other staff (laboratory staff, pharmacists, security, office staff) of hospital having a history of COVID vaccination. Two rounds of the survey were conducted1 month after the first dose of vaccination and 1 month after the second. Participants were selected using a convenience sampling technique separately for each.
