Bharat Biotech, one of the front runners in the race to develop a coronavirus vaccine in India, has released new data from Phase 1/2 clinical trials. The vaccine is still being tested for efficacy – whether it can prevent Sars-Cov-2 infections – but the data shows that it is progressing well. A look at the key indicators and how they compare to some other candidates.
Bharat Biotech’s coronavirus candidate vaccine, jointly developed with the Indian Council of Medical Research (ICMR), passed the two pivotal tests in clinical trials – showing it was safe and triggered an immune response – according to an analysis in an early stage released Wednesday.
The Phase 1/2 data showed that the levels of neutralizing antibodies in those who received the vaccine – called Covaxin – were comparable to those who recovered from natural infection. This level peaked 42 days after the second dose, with a dip at 104 days.
Of all early stage participants who received the vaccine, 98.3% were “sero-converted” (i.e., they developed an antibody response).
But how do these numbers compare to other leading vaccine candidates whose data has been released?
The comparison can be made in two ways: drawing parallels with other candidates who use the same method to train a person’s immunity, or by comparing some parameters with the leading candidates already approved.
Bharat Biotech’s coovaxin is based on an inactivated virus and for the first comparison method there are four others in late stage studies that can be compared. All four of these are being developed by Chinese companies, but only one, Sinovac’s Coronavac, has run analysis that can be pulled up for comparison.
Initially, it seems that the Indian candidate is comparable or even slightly better than its rival in some respects. When people received both doses of Covaxin, 98.4% of them developed antibodies compared on Day 56 to 100% on Day 28 after the two-dose regimen in the Coronavac study, according to the data from the Phase 2 study that were used by both released.
The difference was greater in how strong the level of antibody response was. In the case of Covaxin, volunteers showed levels comparable to those who had a natural infection of Sars-Cov-2 and recovered. But in the case of Coronavac, this level was about a third of that seen in recovered individuals.
Certainly, there may still be some variations in test methods used by researchers and the studies were held separately, in different populations, which do not lend themselves to similar comparisons. But the percentage of people who develop an antibody response and the comparison of antibody levels to recovered (recovering) people are relative parameters that can be used to loosely compare vaccine performance.
Sinovac and Bharat Biotech both evaluated their vaccines for these parameters, while the three other inactivated virus platform candidates in late-stage studies (two from Sinopharm and the third from the Chinese Academy of Medical Sciences) did not have antibody levels compared to recovering patients. .
While the Indian and Chinese candidates have platform overlap and both use a two dose regimen, they also have some differences. For example, the Chinese Coronavac needs a booster shot after 14 days, while the Indian was on day 28.
The two vaccine candidates also use different adjuvants – ingredients used to help create a stronger immune response. Coronavac uses aluminum, a common adjuvant, while Covaxin contains a proprietary adjuvant called Algel-IMDG.
The second method of comparison is to take into account the number of antibodies developed after people receive the Moderna and Pfizer-BioNTech vaccines.
In the case of Moderna, 100% of people developed antibodies and the levels were more than twice as high as in recovering individuals. Also in the case of the Pfizer and BioNTech inoculation, 100% of the individuals developed antibodies and this level was nearly four times.
Both figures are far ahead of Covaxin and Coronavac.