Opinion Measure of confidence

India’s anti-COVID inoculation drive has received a boost with Bharat Biotech’s Covaxin demonstrating more than 80 per cent efficacy in the final phase of clinical trials. The data on the trials, released on Wednesday, are the first interim efficacy figures on an anti-COVID vaccine being developed in the country. The vaccine developed by the Hyderabad-based firm is being used, along with the Serum Institute product, in the inoculation drive currently underway in the country. But it was approved on a “clinical trial” mode — those administered Covaxin are monitored for serious adverse effects and the manufacturer is liable to pay compensation if an event is proved to be linked to the vaccine. This has created hesitancy about Covaxin, with states like Chhattisgarh requesting only Covishield from the Centre. The latest results could go a long way in removing these misgivings.

Efficacy is a crucial requirement during vaccine trials, but it’s also a tricky concept. Experts caution against jumping to easy conclusions about percentages obtained during trials. For example, in the case of Covaxin, it would be wrong to conclude that about 20 per cent of people administered the jab would still be vulnerable to the novel coronavirus. This is because even the most stringent trials are conducted on a limited number of people — about 26,000 in the case of the Bharat Biotech product — and they can only help to arrive at an estimate. But experts do agree that an above 80 per cent result in the interim analysis puts Covaxin on a strong footing in the fight against the virus. As epidemiologist Gagandeep Kang told this paper, “Interim analyses actually test the vaccine much more, so if it has around 81 per cent efficacy, that means it is likely to maintain a high level of efficiency even when the full results are released”.

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Covaxin has not been tested against the mutant strains of the virus that have found their way to the country in the last six weeks. Theoretically, however, vaccines such as Covaxin that rely on an inactivated virus are known to trigger robust immune responses against mutants. This facet of the indigenously-developed vaccine is likely to become clearer in the coming weeks and months. Other data on its relative efficacy amongst different age groups, gender and people with comorbidities will help in arriving at a more comprehensive understanding about Covaxin, further easing the hesitancy around it.