Vaccine efficacy of 80.6% for Bharat Biotech’s Covaxin at the first interim analysis of phase-3 trials in India is indeed promising, though it took two months for the data to become available after the vaccine was approved for ‘restricted emergency use’ by the Indian drug regulator. The vaccine efficacy was measured based on symptomatic COVID-19 disease — mild, moderate or severe — two weeks after the second dose. The interim analysis undertaken at the first endpoint of 43 COVID-19 cases in the phase-3 trial carried out across 26 sites in India found 36 cases in the placebo group while only seven COVID-19 cases in the arm that received two doses of the vaccine given 28 days apart. The phase-3 trial that began last November recruited 25,800 participants, with one half receiving the vaccine and the other, a placebo. While the phase-3 trial will continue till 130 participants in both groups put together develop COVID-19 disease, another interim analysis will be carried out when there are 87 cases. Covaxin’s efficacy of 80.6% at first interim analysis is higher than AstraZeneca/Covishield vaccine efficacy of 55.1% when the second dose is administered less than six weeks after the first; in India, the second dose of Covishield is approved for four-six weeks after the first. Also, the phase-3 trial recruited 2,433 participants over the age of 60 and included 4,500 people with comorbidities. However, those with severe and/or uncontrolled comorbidities were not recruited.
As per the phase-1 data published in The Lancet Infectious Diseases and a preprint of the phase-2 trial, Covaxin appears to be safe and highly immunogenic, and has also been found to be effective against the B.1.1.7 variant first found in Britain. While Covaxin accounts for less than 10% of all COVID-19 vaccinations in India, the absolute number of vaccinations as on March 3 stands at over 1.6 crore. No deaths associated with this vaccine have been reported so far. Though the first interim analysis is based on 43 cases, which is smaller when compared with other vaccines that have been approved by other regulators, the vaccine appears safe and efficacious in phase-3 and early stages of human trials and animal studies. The Indian regulator should therefore revise the restricted emergency use approval such that Covaxin is treated on a par with Covishield and should no longer seek additional precautions in the form of signed consent before vaccination and also remove the label “clinical trial mode” from the approval; their continuation would send a wrong signal about its safety and efficacy. With a narrow window of opportunity available to vaccinate people before a second wave probably sets in or dangerous variants get established, India can ill afford to have roadblocks in the uptake of either vaccine.