What is the difference between Covaxin (inactivated vaccine) and Covishield (recombinant vaccine)?

Difference Between Covaxin and Covishield

Covishield is more effective than Covaxin, with higher antibody responses (98.3% vs 74.4% seroconversion rate in seronegative individuals) and greater protection against COVID-19 variants including delta and omicron. 1

Vaccine Platform and Development

• Covaxin (BBV152) is an inactivated vaccine developed by Bharat Biotech in collaboration with the National Institute of Virology (NIV) and ICMR in India 2
• Covishield (AZD1222) is a recombinant adenovirus vector-based vaccine developed by the Serum Institute of India (SII), Oxford University, and AstraZeneca 2
• Covaxin uses the traditional method of vaccine formulation with adjuvanted inactivated viral particles, while Covishield uses an adenovirus vector to deliver the SARS-CoV-2 spike protein genetic material 3

Efficacy and Immune Response

• Covishield demonstrates higher effectiveness (approximately 90%) compared to Covaxin (78-81%) 2
• In head-to-head comparisons, Covishield elicits significantly higher antibody responses than Covaxin as measured by:
  • Seroconversion rate: 98.3% vs 74.4% in seronegative individuals (p<0.0001) 1
  • Anti-spike antibody levels: 1272.1 vs 75.4 binding antibody units/ml in seronegative individuals (p<0.0001) 1
• Covishield generates both CD4+ and CD8+ spike-specific T cells, whereas Covaxin primarily elicits CD4+ spike-specific T cells 1

Dosing Schedule

• Covaxin requires a shorter interval between doses (4-6 weeks) compared to Covishield (12-16 weeks) 2
• Both vaccines are administered as a two-dose series 2

Protection Against Variants

• Covishield demonstrates higher surrogate neutralizing antibody responses against variants of concern, including delta and omicron variants 1
• Covaxin might theoretically maintain effectiveness against future variants with significant spike protein changes due to its ability to produce multiple antibodies against various epitopes, though this remains theoretical 3

Real-World Effectiveness

• In healthcare workers in Mumbai, India, Covishield showed 70% effectiveness (95% CI: 61%-77%) in preventing breakthrough infections 4
• The effectiveness increased to 88% (95% CI: 80%-93%) in those with previous COVID-19 infection plus complete vaccination 4
• Another study showed that Covishield provided 54% (95% CI: 27%-71%) protection against COVID-19 after two doses, with 95% (95% CI: 44%-100%) protection against moderately severe disease requiring oxygen therapy 5

Safety Profile

• Both vaccines have demonstrated acceptable safety profiles in clinical trials and real-world settings 4
• No major side effects have been reported in healthcare personnel receiving either vaccine 4

Practical Considerations

• Both vaccines have been widely used in India's vaccination campaign that began in January 2021 3
• Covishield has been more widely administered in India, with one study showing 99% of healthcare workers received Covishield versus only 0.9% receiving Covaxin 4

Hybrid Immunity

• Previous COVID-19 infection plus complete vaccination provides significantly higher protection (88%) compared to vaccination alone (70%) 4
• This enhanced protection was observed primarily with Covishield, as it was the predominant vaccine used in the study population 4