Hyderabad,  Bharat Biotech on Wednesday announced the first interim analysis of Covaxin, which shows the efficacy of the Covid-19 vaccine to be at 81 per cent.

The Hyderabad-based vaccine maker said whole virion inactivated Covid-19 vaccine candidate demonstrated an interim vaccine efficacy of 81 per cent in its Phase 3 clinical trial.

The trials involved 25,800 subjects, the largest ever conducted in India, in partnership with the Indian Council of Medical Research (ICMR).

"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 demonstrates high clinical efficacy trend against Covid-19 but also significant immunogenicity against the rapidly emerging variants," said Dr. Krishna Ella, Chairman and Managing Director, Bharat Biotech.

BBV152 (Covaxin) contains a whole virion inactivated SARS-CoV-2 vaccine, which is produced in Vero cells. It is stable at 2 to 8oC (refrigerated) and is shipped in a ready-to-use liquid formulation that permits distribution using existing vaccine supply chain channels. BBV152 has a 28-day open vial policy as a unique product characteristic, thus reducing vaccine wastage by approximately 10-30 per cent, the vaccine maker said.

BBV152 is based on an established manufacturing platform with a better safety profile when compared to other vaccine platforms. The inclusion of the Algel-IMDG adjuvant enhances T-cell immune responses to Covid-19, leading to long-term protection.

"I want to thank every one of the participants, who volunteered to participate in this vital clinical trial, our partners, principal investigators across 25 study sites, and our team at Bharat Biotech who dedicated their time to this vaccine discovery," said Suchitra Ella, Joint Managing Director, Bharat Biotech.

The Phase 3 study enrolled 25,800 participants between 18-98 years of age, including 2,433 over the age of 60 and 4,500 with comorbidities. The primary endpoint of Phase 3 clinical trial is based on the first occurrence of PCR-confirmed symptomatic (mild, moderate, or severe) Covid-19 with onset at least 14 days after the second study vaccination in serologically negative (to SARS-CoV-2) adult participants at baseline.

The first interim analysis is based on 43 cases, of which 36 cases of Covid-19 were observed in the placebo group versus 7 cases observed in the BBV152 group, resulting in a point estimate of vaccine efficacy of 80.6 per cent.

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.

Analysis from the National Institute of Virology indicates that vaccine-induced antibodies can neutralize the UK variant strains and other heterologous strains, which has been published in bioRxiv.

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, Bharat Biotech said.

More than 40 countries globally have expressed their interest in Covaxin. These countries are highly satisfied with the safe, inactivated vaccine technology and robust data package for safety and immunogenicity, it added.