According to the first real-world assessment of India’s indigenous COVID-19 vaccine published in The Lancet Infectious Diseases journal, two doses of Covaxin are 50% effective against symptomatic disease. 

Two doses of Covaxin, also known as BBV152, were found to have 77.8% efficacy against symptomatic disease in an interim study recently published in The Lancet, with no serious safety concerns.

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From April 15 to May 15, researchers at the All India Institute of Medical Sciences (AIIMS) in Delhi assessed 2,714 hospital workers who were symptomatic and underwent a COVID-19 RT-PCR test. 

The Delta variant was the most common strain in India during the study period, accounting for about 80% of all confirmed COVID-19 cases, according to the researchers.

Covaxin is an inactivated whole virus vaccine developed by Hyderabad-based Bharat Biotech in collaboration with the National Institute of Virology, Indian Council of Medical Research (NIV-ICMR), Pune. It is given in a two-dose regimen 28 days apart. 

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Covaxin was approved for emergency use in India for people aged 18 and up in January of this year. The vaccine was added to the World Health Organization’s (WHO) list of approved COVID-19 vaccines for emergency use earlier this month.

The most recent study was conducted in healthcare workers who were primarily offered Covaxin during India’s second COVID-19 outbreak.

“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, Additional Professor of Medicine at AIIMS New Delhi, told NDTV. 

“Our findings add to the growing body of evidence that rapid vaccine rollout programmes remain the most promising path to pandemic control while public health policies must continue to include additional protective measures, such as mask-wearing and social distancing,” Soneja said in a statement.

Beginning January 16 of this year, the COVID-19 vaccination centre at AIIMS New Delhi offered Covaxin exclusively to all of its 23,000 employees. 

The vaccine’s effectiveness against symptomatic RT-PCR confirmed SARS-CoV-2 infection was tested. 

SARS-CoV-2 infection, the virus that causes COVID-19, was found in 1,617 of the 2,714 employees tested positive, while 1,097 tested negative.

The results of positive RT-PCR tests were compared to the results of negative RT-PCR tests (controls). 

The odds of receiving Covaxin vaccination were compared between cases and controls, with occupational exposure to COVID-19, prior SARS-CoV-2 infection, and infection dates taken into account. 

The vaccine’s effectiveness against symptomatic COVID-19 was found to be 50% after two doses of Covaxin, with the second dose administered 14 or more days before RT-PCR testing.

According to the researchers, the effectiveness of two vaccine doses remained relatively stable over a seven-week follow-up period. 

They found that the first dose’s adjusted vaccine effectiveness was low after seven and 21 days, which is consistent with the performance of other Delta variant preventives, they said.

“Findings from the study confirm previous research indicating that two doses of BBV152 are required to achieve maximum protection and that all vaccine roll-out plans must follow the recommended dosing schedule,” said Parul Kodan, Assistant Professor of Medicine at AIIMS New Delhi.

“More research is needed to better understand how these findings translate to BBV152’s effectiveness against delta and other variants of concern, especially related to severe COVID-19 infection, hospitalisation, and deaths,” Kodan said.

The authors recognize that the vaccine efficacy estimated in this study differs from the efficacy reported in a recently published phase 3 trial. They speculated that a number of factors could be to blame for the new study’s lower vaccine effectiveness. 

According to the researchers, this study only included hospital employees who may be at a higher risk of COVID-19 infection than the general public. 

They said the study was carried out at the height of India’s second wave of COVID-19, which had high test positivity rates among hospital employees and Delhi residents.