The wait for published data on the final phase 3 clinical trials of Covaxin is getting longer despite a growing clamour to release it, amid new information that compared to Covishield, it may be triggering lower antibody response to Covid-19.
Bharat Biotech, which has developed Covaxin, with support from ICMR, said the final analysis of its efficacy trials between November – January, will be made public only in July, after it is submitted to the drug regulator and peer reviewed journals with a timeline of about three months for publication.
While announcing the second interim analysis of it’s phase 3 trial on April 20, the company had said that safety and efficacy results from the final analysis will be available in June, and the final report will be submitted to a peer- reviewed publication.
In the April statement, the company has claimed the vaccine has shown a 78% efficacy against preventing infection while efficacy against severe Covid-19 disease was 100%, with an impact on reduction in hospitalisations after accrusing 127 symptomatic cases. This efficacy was lower by 3% from the one claimed in another statement to the press, issued in early March, based on 87 symptomatic cases.
But a delay in sharing the final data is bothering many, since phase 3 trial data of all other approved Covid vaccines, including the Russian Sputnik were published within 4-6 weeks of interim analysis.
Also, Covaxin had been approved by the Central Drugs Standard Control Organization for public use in clinical trial mode while still under efficacy trials on 25800 people. It is unusual to have such a delay, particularly when the second analysis was so close to the sample size of 130 symptomatic cases, said a top virologist who did not wish to be namedm Health systems and vaccine policy expert Chandrakant Lahariya said while publication in a journal may take time, the company should at least release the findings on a pre-print server.
A recent comparative evaluation of responses to spike protein after the fisrt and second doses of Covaxin and Covishield showed the former may have lower immunogenicity.