Covaxin Was Only 50% Effective During Delta Wave, Shows Real-World Study

At the start of the country's vaccination campaign in January, staff at AIIMS had exclusively been offered Covaxin.

Covaxin, one of the main vaccines used in India's coronavirus immunization drive, provides only 50% protection against symptomatic COVID-19, according to a real-world study that suggests the shot is less effective than initially thought.

As India was slammed by its second major Covid wave earlier this year, researchers at the All India Institute of Medical Sciences in Delhi analyzed data from 2,714 of the hospital's health workers who were showing signs of infection and underwent RT-PCR testing between April 15 and May 15, according to a study published in The Lancet Infectious Diseases journal. At the start of the country's vaccination campaign in January, staff at AIIMS had exclusively been offered Covaxin, a shot co-developed by India's state-funded health research agency and local company Bharat Biotech International Ltd.

The authors found that two weeks or more after completing a two-dose regime the vaccine's adjusted effectiveness against symptomatic Covid was lower than the 77.8% that interim results established during final stage tests, a study of which was published in The Lancet earlier this month. High infection rates and virus exposure among the hospital's employees may have contributed to Covaxin's weaker real-world efficacy, along with the possibility that the then recently emerged delta variant blunted the shot's protection, the researchers said.

"Our study offers a more complete picture of how BBV152 performs in the field and should be considered in the context of Covid-19 surge conditions in India, combined with the possible immune evasive potential of the delta variant," Manish Soneja, an additional professor of medicine at AIIMS in New Delhi, said in a statement referring to the vaccine's scientific name.