Covishield was effective against Covid in India amid Delta-led surge: Study

The vaccine effectiveness of complete vaccination against moderate-to-severe disease was much higher at 81%, says Lancet study

The findings of a new study show the real-world vaccine effectiveness of Covishield against SARS-CoV-2 during the second wave of the Covid pandemic between April and May this year was 63% in India, the Ministry of Science & Technology said.

The study, published in The Lancet Infectious Diseases, was carried out by a multi-institutional team of Indian researchers led by Translational Health Science and Technology Institute (THSTI). 

The effectiveness of complete vaccination through Covishield against moderate-to-severe Covid-19 was much higher at 81%, the study found. The vaccination programme in India is driven largely by Covishield.

The researchers employed a comparison between 2,379 cases of confirmed SARS-CoV-2 infection and 1,981 controls. They also assessed neutralising activity and cellular immune responses against the variants in healthy vaccinated people to understand the mechanisms of protection.

The scientists observed that the spike-specific T-cell responses were conserved against both the delta variant and wild-type SARS-CoV-2. Such cellular immune protection might compensate for waning humoral immunity against the virus variants and prevent moderate-to-severe disease and need for hospitalisation, the ministry said.

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

Covid-19 has affected more than 200 million people causing more than 5 million deaths worldwide, according to the World Health Organization (WHO). The rise in mutant variants of the SARS-CoV-2 virus has led to concerns regarding vaccine effectiveness. Delta (B.1.617.2) variant is the predominant strain in India.