Explained: What Covaxin’s 81% interim vaccine efficacy means?

Bharat Biotech on Wednesday announced its Covid-19 vaccine candidate BBV152 Covaxin demonstrated 81% interim vaccine efficacy in its Phase 3 clinical trial.

Explained: What Covaxin’s 81% interim vaccine efficacy means?

New Delhi: Bharat Biotech on Wednesday announced its Covid-19 vaccine candidate BBV152 Covaxin demonstrated 81% interim vaccine efficacy in its Phase 3 clinical trial. While the results are very encouraging and expected to boost confidence in the indigenously developed vaccine, however, it is important to understand that these are the first interim results based on 43 cases infected with the Covid-19 virus and the final results will determine the actual efficacy. Interim results from clinical trials help to analyze and predict the outcomes of a clinical trial.

According to the Bharat Biotech, of the 43 cases around 36 cases of Covid-19 were observed in the placebo group versus 7 cases observed in the Covaxin group, resulting in a point estimate of vaccine efficacy of 80.6%. The data is yet to be peer-reviewed.

An additional interim analysis is awaited for 87 cases, and the final analysis is planned for 130 covid positive cases to analyse the actual efficacy data.

To understand the vaccine efficacy, the study needs to continue till the predecided number of trial participants report Covid-19 infection. In the case of Covaxin, there have to be 130 trial participants who get infected with the Covid virus, and after studying how many were from the placebo arm versus BBV152 COVAXIN arm can the final efficacy be found.

The Hyderabad-based vaccine manufacturer in partnership with the Indian Council of Medical Research began the phase 3 study of Covaxin in November 2020 across 25 study sites and was conducted on a total of 25,800 participants between 18-98 years of age, including 2,433 over the age of 60 and 4,500 with comorbidities.

The results are crucial as this is the largest ever clinical trial for Covid-19 in India and would provide data on how well the vaccine protects the younger and older age groups and also those with comorbidities.

Covaxin Phase 1 and Phase 2 clinical trials conducted in 755 participants demonstrated high safety profile of the candidate vaccine with seroconversion rates of 98.3% and 81.1% on day 56 and 104 respectively.

The vaccine is stable at 2-8 degrees Celsius has also shown efficacy against the UK strain of the virus.

The interim result is expected to reduce the hesitancy and doubts in people that cropped after the vaccine was granted approval in January 2020 without the phase 3 efficacy data.

Currently, Covaxin and Covishield are the two vaccine candidates that are being administered to people in India as part of the nationwide Covid-19 vaccination drive which began on January 16. On March 1, India began the second phase of vaccination for people above 60 years of age and people above 45 years with comorbidities.


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