Coronavirus | Covaxin efficacy is 81%, works against variants

Interim analysis based on 43 cases; low adverse events.

March 03, 2021 05:44 pm | Updated December 02, 2021 11:00 pm IST - Hyderabad

Covaxin vaccine. File

Covaxin vaccine. File

Covaxin, India’s first COVID-19 vaccine, has demonstrated an interim clinical efficacy of 81% in the phase 3 clinical trial, vaccine maker Bharat Biotech said on Wednesday.

The vaccine demonstrated high clinical efficacy and significant immunogenicity against variants, the company’s CMD, Krishna Ella, said.


A statement from Bharat Biotech, which developed the vaccine in collaboration with Indian Council of Medical Research (ICMR), said 25,800 participants between 18-98 years of age were enrolled for the Phase 3 study. It included 2,433 over the age of 60 and 4,500 with comorbidities.

The first interim analysis is based on 43 cases, of which 36 cases of COVID-19 were observed in the placebo group versus seven cases observed in the Covaxin group, resulting in a point estimate of vaccine efficacy of 80.6%. 

The interim analysis included a preliminary review of the safety database, which showed that severe, serious, and medically attended adverse events occurred at low levels and were balanced between vaccine and placebo groups. The trial's conduct and monitoring are as per Good Clinical Practice guidelines and have been outsourced to IQVIA.


A  release said analysis from the National Institute of Virology indicates that vaccine-induced antibodies can neutralize the UK variant strains and other heterologous strains.

Noting that the vaccine demonstrated the interim efficacy in preventing COVID-19 in those without prior infection after the second dose, the company said the 25,800 participants received a vaccine or placebo in a 1:1 ratio. Clinical trials will continue through to final analysis at 130 confirmed cases in order to gather further data and to evaluate the efficacy of Covaxin in additional secondary study endpoints.

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Mr.Ella said, “Today is an important milestone in vaccine discovery, for science and our fight against coronavirus. With today’s results from our Phase 3 clinical trials, we have now reported data on our COVID-19 vaccine from Phase 1, 2, and 3 trials involving around 27,000 participants.”

Covaxin (BBV152) contains a whole virion inactivated SARS-CoV-2 vaccine, which is produced in Vero cells. It is based on an established manufacturing platform with a better safety profile when compared to other vaccine platforms, the release said.


It is one of the two vaccines approved for use in the country thus far and is being used as part of the immunisation programme rolled out on January 16, starting with the frontline healthcare workers. The Drugs Controller General of India (DCGI) had given the emergency use authorisation for the vaccine in clinical trial mode.

In the second phase immunisation programme, which kicked off recently, Prime Minister Narendra Modi was among those who took the first dose along with many of his Cabinet ministers. The two dose vaccine, taken 28 days apart, is stable at 2 to 8°C (refrigerated) and shipped in a ready-to-use liquid formulation that permits distribution using existing vaccine supply chain channels. 


The release said Bharat Biotech expects to share further details of the trial results as additional data become available. An additional interim analysis is planned for 87 cases, and the final analysis is planned for 130 cases. All data from the second interim and final analyses will be shared via pre-publication servers as well as submitted to a peer-reviewed journal for publication.

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