Covishield vaccine remained effective against moderate-to-severe COVID-19 even during the deadly surge dominated by the highly transmissible delta variant of SARS-CoV-2, according to a study published in The Lancet Infectious Diseases journal.
The Lancet study was meant to evaluate real-world effectiveness of Covishield during the devastating surge between April-May in India that put the health infrastructure under tremendous strain.
The vaccine efficacy in fully vaccinated individuals, said the Lancet, was found to be at 63 per cent.
During the moderate to severe disease phase, the vaccine efficacy was found to be at 81 per cent, it said.
The findings come even as a new Covid variant - Omicron or the B.1.1.529 was detected in South Africa last week and designated by the World Health Organisation (WHO) as a ''variant of concern'' - has set off alarm bells across the world.
On Monday, the WHO said the Omicron variant poses a "very high" risk globally, stressing that uncertainties remained about how contagious and dangerous the strain was.
Covishield-maker Serum Institute of India has resumed vaccine exports for distribution to low- and middle-income nations under the global vaccine-sharing programme COVAX.
The total number of Covishield doses manufactured so far has crossed the 1.25 billion mark, according to the Pune-headquartered company.
Earlier this month, the WHO added the vaccine to its list of approved emergency use COVID-19 vaccines.