Anti SARS-CoV 2 IgG antibody response in fully vaccinated Covishield (AZD1222) and Covaxin (BBV-152) recipients: a study done in southern part of West Bengal, India

Vaccination being the only way to reduce mortality from the dreaded COVID-19 disease, the vaccine was introduced in India as per the advice of the National Expert Group on January 16, 2021. Duration of immune response elicited by the vaccines has always been a matter of content. With new variants emerging every other day, the study was done to look for the antibody response in vaccine recipients post second dose of vaccination.

A longitudinal observational study was conducted from August 2021 to February 2022 in fully vaccinated individuals who took either Covishield (AZD1222) or Covaxin (BBV-152). Blood was collected from the individuals at 12-16 weeks post-vaccination to look for IgG antibody response against S1 spike protein of SARS-CoV2 by ELISA. Follow-up was done at 32 weeks post the second dose in individuals who had received Covishield.

Among 176 individuals, IgG antibody against S1 spike protein was found to be positive in 89.7% (158). Covishield recipients showed higher antibody response (99.1%) as compared to Covaxin recipients (71%). Antibody response was higher in males, individuals less than 50 years, and non-comorbid individuals. Of 38 Covishield recipients, IgG antibody response was positive in 28 (73.6%) individuals when followed up at 32 weeks post the second vaccination dose.

The study gives us input with regard to the long-term antibody kinetics of both vaccines. The study has a follow-up plan to co-relate the antibody response to the neutralization test.