Data collected from hospital workers has revealed that Bharat Biotech's COVID-19 vaccine, Covaxin, was only 50% effective at preventing symptomatic COVID-19 in a high-risk population during a devastating second wave of infections in India this year, Reuters news agency reported on Wednesday.

The real world study for Covaxin, conducted from 15 April to 15 May 2021 compares with a 77.8% effectiveness rate in a late-stage trial of more than 25,000 participants that was conducted November 2020 to January 2021.

According to the study, which was published in the Lancet Infectious Diseases journal, this new data analysed just over 1,000 COVID-19 cases with a test-negative control case group, matching by age and gender.

The study concluded that the much lower effectiveness rate for the two-dose shot seen in this new study can possibly be attributed to the fact that the study was restricted to hospital employees who had a higher risk of being infected than the general population, that it was conducted during a surge in infections and also to the prevalence of the Delta virus variant at the time.