Detection of neutralizing antibody towards spike protein of SARS-Cov-2 in vaccinated subjects

Background: The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged in December 2019 in Wuhan, China causing a severe acute respiratory disease (COVID-19). The virus has rapidly spread into a pandemic affecting over more than 40 million & mortality more than 5 million as per recent data.Due to lack of specific treatment vaccination was considered as main measures to control the pandemic. India’s drugs regulator, Drugs Controller General of India (DCGI) authorized emergency use for AZD1222/Covishield (ChAdOx1-Recombinant) and BBV152/Covaxin in January 2021 and vaccination was started beginning with healthcare and frontline workers and to all aged above 18 years. The present study aimed to know the presence of neutralizing antibodies in vaccinated subjects with or without history of infection by SARSCov-2. Materials & Methods: After obtaining Institutional Ethical Clearance 260 Vaccinated subjects who consented to participate were included for the study. Details were recorded in the proforma. After sterile precaution about 2 ml blood sample was collected in plain vacutainer tube & Serum sample was separated and stored at -20 0C. The neutralizing antibody towards spike protein was detected by performing commercial ELISA (MICROLISA, J MITRA) according to the manufacturer’s guidelines. The results were interpreted by calculating Inhibition rate which is above 30% was considered as positive. Result: Among 260 vaccinated subjects 197(75.6%) positive for neutralizing antibody. Among them 178(76.2%) were Covishield and 82(74.07%) Covaxin vaccinees. Age & sex distribution were recorded the highest in 18-40 years 35 106(53.8%) & female 61(54.4%). Vaccinated and infected 151(86.2%) & only vaccinated 46(54.1%). Good antibody titre was observed in 78.5% upto 4 months of vaccination. Conclusion: The vaccinated subjects with history of SARS-cov-2 infection showed better neutralizing antibody titre with good percentage of persistence Nab till 4th months of post vaccination period.