Covaxin: New study finds India’s homegrown vaccine was only 50% effective during second wave

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India’s homegrown Covid-19 vaccine Covaxin was only 50 per cent effective against symptomatic infections during the peak of the country’s deadly second wave, much lower than the efficacy established during earlier tests, according to new research.

This is the first real-world assessment of Covaxin, which is one of the two main vaccines being used in India’s inoculation drive.

The study included 2,714 health workers from Delhi’s All India Institute of Medical Sciences, who were showing signs of infection and underwent RT-PCR testing between 15 April and 15 May, the peak of India’s second wave of coronavirus crisis. The study was published in The Lancet medical journal on Tuesday.

All the medical workers were inoculated with two doses of Covaxin at least 14 days before, and had a high risk of exposure to the virus.

The study said that half the participants were found to have symptomatic Covid-19 as confirmed by RT-PCR tests.

Researchers found that the adjusted effectiveness of Covaxin against symptomatic Covid-19 was at 50 per cent overall, lower than the 77.8 per cent that interim tests results, also published in The Lancet earlier this month, showed.

After excluding participants with previous Covid-19 infections, the adjusted effectiveness dropped to 47 per cent.

The increased exposure of medical staff and the emergence of the Delta variant, which was more virulent and was known to break vaccine protection, could be a few reasons for decreased efficacy, researchers believe.

“Our study offers a more complete picture of how BBV152 [Covaxin] 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.

Real-world assessments generally show lower efficacy rates for vaccines compared to clinical data and are believed to be more reliable to gauge the efficacy of the jab on the masses.

Moreover, almost all vaccines showed lower efficacy rates against the deadly Delta variant, and the study only focused on the two-week phase during India’s second Covid-19 wave, which was presumably dominated by the potentially immune-evasive variant.

Researchers said the data isn’t discouraging and concluded that they supported the ongoing rollout of the vaccine to help control the spread of Covid-19.

The vaccine, developed by Hyderabad-based Bharat Biotech, was recently approved by WHO’s technical committee and was included in the list of acceptable vaccines, but only after a wait of four months.

The Indian government has been promoting the vaccine among healthcare workers, and so far, 138 million doses have been administered in India.

However, the vaccine’s rollout was marked by controversy as it was approved in the country before its third trial data was released.