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Reading the Clues from Covaxin’s Early Trial Data


Bharat Biotech, which is among the pioneers in the race to develop a coronavirus vaccine in India, published new data from phase 1/2 clinical trials. The vaccine is still being tested to determine its efficacy, whether it can prevent Sars-Cov-2 infections, but data shows that it is progressing well. A look at the key metrics and how you might stack up against other candidates.

Bharat Biotech’s coronavirus candidate vaccine, developed jointly with the Indian Council for Medical Research (ICMR), passed the two crucial tests in clinical trials, which proved it was safe and elicited an immune response, according to a published early-stage analysis. on Wednesday.

Data from Phase 1/2 showed that the levels of neutralizing antibodies in those who received the vaccine, called Covaxin, were similar to those who recovered from a natural infection. This level peaked 42 days after the second dose, with a drop at 104 days.

Reading the Clues from Covaxin's Early Trial Data

Among all participants in the initial phase who received the vaccine, 98.3% “seroconverted” (that is, they developed an antibody response).

But how do these numbers compare to other leading vaccine candidates whose data has been published?

The comparison can be done in two ways: by drawing parallels with other candidates who use the same method to train a person’s immunity, or by comparing some of the parameters with the already approved lead candidates.

Coovaxin from Bharat Biotech is based on an inactivated virus, and for the first comparison method, there are four others in late stage trials that can be compared. All four are being developed by Chinese companies, but only one, Sinovac’s Coronavac, has carried out an analysis that can be taken for comparison.

At first, it seems that the Indian candidate may be comparable or even slightly better than his rival in some parameters. When people received both doses of Covaxin, 98.4% of them developed antibodies compared to day 56 and 100% on day 28 after the two-dose regimen in the Coronavac trial, based on data from the phase 2 trial posted by both.

Reading the Clues from Covaxin's Early Trial Data

The difference was most marked when it came to how strong the antibody response level was. In the case of Covaxin, the volunteers showed levels similar to those with a natural Sars-Cov-2 infection and recovered. But in Coronavac’s case, this level was about a third of what was seen in recovered people.

To be sure, there could still be some variations in the testing methods used by the researchers and the studies were carried out separately, in different populations, which do not lend themselves to similar comparisons. But the proportion of people who develop an antibody response and the comparison of antibody levels with recovered (convalescent) people are relative parameters that can be used to vaguely compare vaccine performance.

Sinovac and Bharat Biotech judged their vaccines based on these parameters, while the other three candidates for the inactivated virus platform in late-stage trials (two of them are from Sinopharm and the third from the Chinese Academy of Medical Sciences) have not compared the levels of antibodies with those of convalescent patients. .

While the Indian and Chinese candidates have a platform overlap and both use a two-dose regimen, they also have some differences. The Chinese Coronavac, for example, requires a booster injection at 14 days, while the Indian was at 28 days.

The two candidate vaccines also use different adjuvants, ingredients that are used to help create a stronger immune response. Coronavac uses aluminum, which is a commonly used adjuvant, while Covaxin incorporates a proprietary adjuvant called Algel-IMDG.

Reading the Clues from Covaxin's Early Trial Data

The second method of comparison is to take into account the amount of antibodies developed after people received the Moderna and Pfizer-BioNTech vaccines.

In Moderna’s case, 100% of the people developed antibodies, and the levels were more than double the levels seen in convalescent individuals. In the case of the Pfizer and BioNTech inoculation as well, 100% of the people developed antibodies and this level was close to four times.

Both numbers are well ahead of Covaxin and Coronavac.

Original source