The Covishield vaccine effectiveness against SARS-CoV-2 infection in fully vaccinated individuals was found to be 63 per cent during the second wave, according to a study.

The vaccine effectiveness of complete vaccination against moderate-to-severe disease was even much higher at 81 per cent, says the result of the study published in journal "The Lancet Infectious Diseases". To estimate the effectiveness of two doses of the vaccine, 2,379 confirmed cases and 1,981 healthy individuals were analysed.

A multi-institutional team of Indian researchers led by Translational Health Science and Technology Institute (THSTI) evaluated the real-world vaccine effectiveness of Covishield during the SARS-CoV-2 infection surge between April and May, 2021, in India. They also assessed neutralising activity and cellular immune responses against the variants in healthy vaccinated persons to understand the mechanisms of protection.

The scientists also 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, underlined the study.

The study provides comprehensive data on the real-world vaccine effectiveness and immunological response to vaccination which should help guide policy. The study thus implies that the vaccines continued to be effective in protecting against severe disease and death regardless of the variants.

Meanwhile, India has started projecting declining trends in daily Covid caseload. India reported 6,990 fresh Covid cases in the past 24 hours, below the 10,000-mark for fourth consecutive day, on Thursday. The active caseload stands at 1,00,543, lowest in the last 546 days.