Document Type : Research Article
Background: SARS CoV-2 infection has become a major public health concern. India started Covid-19 vaccination from January 16, 2021, after the approval of two candidate vaccines namely COVISHIELD ™ and COVAXIN ™. The present study was conducted to see the neutralizing antibody response to trimeric S protein of SARS CoV-2 in health care workers (HCWs) with 2 doses of COVISHIELD vaccination in a tertiary care hospital.
Methodology: A prospective cohort study was conducted among 156 healthy adult health care workers in a tertiary care centre, vaccinated during January-March 2021. They were divided into two groups, the first group comprised of individuals who were previously RT-PCR positive (n=36) for SARS CoV-2, and second group comprised of those who were RT-PCR negative (n=120). Blood samples were collected from all participants, the first sample on the day of vaccination, second sample after 4 weeks of vaccination, and third after 8 weeks of vaccination to measure the IgG antibodies against the SARS CoV-2 ‘S’ protein using a chemiluminescent quantitative immunoassay.
Results: The spike protein-specific IgG antibody titre was demonstrated reactive cut-off in 98.3% of the participants after 2 doses of vaccine. The median antibody titre declined from 710.5 (IQR, 338.5-1577.5) to 266 (IQR, 116-557.75) in RT-PCR positive HCWs after 8 weeks of vaccination whereas it increased from 45.1 (IQR, 31.475-76.575) to 83.4 (IQR, 52.075-104) in RT-PCR negative HCWs.
Conclusion: We could demonstrate the development of an adequate spike protein-specific IgG titre against SARS CoV-2 following vaccination with 2 doses of COVISHIELD in HCWs.