Covishield remained effective even during Delta surge in India, suggests Lancet study

A new study in the Lancet indicates that the Covishield vaccine against coronavirus remained effective during the Delta variant outbreak in India earlier this year. The vaccine had an efficacy of 63 per cent in fully vaccinated people, while it was 81 per cent effective against moderate-to-severe disease.

Conducted by Indian researchers, the study was led by the Translational Health Science and Technology Institute (THSTI) to evaluate the real-world vaccine effectiveness of Covishield during the SARS-CoV-2 infection surge between April and May 2021. "The rise in mutant variants of SARS-CoV-2 virus has led to concerns regarding vaccine effectiveness. The Delta (B.1.617.2) variant is the predominant strain in India," the Ministry of Science & Technology said in a statement.

"The ChAdOx1 nCoV-19 vaccine remained effective against moderate-to-severe COVID-19, even during a surge that was dominated by the highly transmissible delta variant of SARS-CoV-2," the paper concluded.

They assessed neutralising activity and cellular immune responses against the variants in healthy vaccinated persons to understand the mechanisms of protection. Researchers found that the Spike-specific T-cell responses were conserved against both the delta variant and wild-type SARS-CoV-2.

The study included a comparison between 2379 cases of confirmed SARS-CoV-2 infection and 1981 controls. Published in the journal The Lancet Infectious Diseases, the study found that cellular immune protection might compensate for waning humoral immunity against the virus variants and prevent moderate-to-severe disease and the need for hospitalisation.

"This study provides comprehensive data on the real-world vaccine effectiveness and immunological response to vaccination which should help guide policy," the Ministry added.

Covishield has remained the predominant candidate in inoculating Indians.