A recent study led by the National Centre for Biological Sciences (NCBS) sheds light on the varying effectiveness of Covaxin and Covishield, the two primary COVID-19 vaccines administered in India. This study aims to offer insights into post-vaccination immunity and shape future vaccine strategies.

Introduction

As India’s vaccination drive commenced in April 2021 amidst the delta wave of the COVID-19 pandemic, more than 2.2 billion doses of vaccines have been administered. The study compared Covaxin, developed by Bharat Biotech, and Covishield, manufactured by the Serum Institute of India, across four clinical sites.

Study Methodology

• The study involved 691 participants across four clinical sites, spanning from June 30, 2021, to January 28, 2022.
• Participants received either Covaxin or Covishield as per the government’s mandate, with different dosing intervals.
• Covaxin is an inactivated viral vaccine, while Covishield is a viral vector vaccine.
• The vaccine groups were further categorized into seropositive and seronegative participants based on prior exposure to the virus.

Key Findings

Antibody Response

• Covishield elicited higher levels of antibodies against various SARS-CoV-2 strains compared to Covaxin.
• In seronegative individuals, Covishield showed near-complete seroconversion rates (98.3% – 100%) compared to 74.4% for Covaxin.
• Similarly, seroconversion rates were higher in seropositive individuals for Covishield (91.7%) compared to Covaxin (66.9%).

T Cell Response

• Covishield induced stronger CD4 and CD8 T cell responses compared to Covaxin.
• Covaxin primarily induced CD4 T cell responses against the spike protein in seronegative participants.

Implications and Future Strategies

• The study provides valuable insights into post-vaccination immunity and may influence future vaccine strategies.
• Understanding the differential effectiveness of vaccines could guide policymakers in optimizing vaccination campaigns.
• Further research and studies are warranted to enhance our understanding of vaccine efficacy and immunity.

Conclusion

The study underscores the varying effectiveness of Covaxin and Covishield in eliciting immune responses. Covishield demonstrates higher antibody levels and T cell responses compared to Covaxin, highlighting the importance of continued research to optimize vaccination strategies and combat the COVID-19 pandemic effectively.

Source: Down to Earth