Bharat Biotech, which is among the leaders in the race to develop a coronavirus vaccine in India, has published new data from phase 1/2 clinical trials. The vaccine is still being tested for efficacy – if it can prevent Sars-Cov-2 infections – but data show that it is progressing well. A look at key indicators and how they might compare to other candidates.
The Bharat Biotech coronavirus vaccine candidate, developed jointly with the Indian Medical Research Council (ICMR), passed the two crucial tests in clinical trials – showing that it is safe and triggered an immune response – according to the early stage analysis published on Wednesday.
Phase 1/2 data 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 at 42 days after the second dose, with a decrease observed at 104 days.
Of all the early participants who received the vaccine, 98.3% were “sero-converted” (ie, developed an antibody response).
But how do these figures compare to other top candidates whose data have been published?
The comparison can be made 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 main candidates.
Coovaxine from Bharat Biotech is based on an inactivated virus, and for the first method of comparison, there are four others in the late-stage studies that can be compared. All four are developed by Chinese companies, but only one, Coronavac, of Sinovac, performed an analysis that can be taken for comparison.
At first glance, it seems that the Indian candidate may be comparable or even slightly better than his rival in some parameters. When people were given both doses of Covaxin, 98.4% of them developed antibodies, compared to day 56 to 100% on day 28, after the two-dose regimen in the Coronavac study, according to published Phase 2 study data. of both.
The difference was stronger when it came to how strong the antibody response level was. In the case of Covaxin, the volunteers had similar levels to those who had a natural Sars-Cov-2 infection and recovered. But in the case of Coronavac, this level was about a third of what was seen in people recovered.
Certainly, there could still be some variations of the testing methods used by the researchers, and the studies were conducted separately, in different populations, which do not allow similar loans. 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 on the basis of these parameters, while the other three inactive candidates of the viral platform in the late studies (two of them are from Sinopharm and the third from the Chinese Academy of Medical Sciences) did not compare the levels. of antibodies with convalescent patients.
While Indian and Chinese candidates have an overlapping platform and both use a two-dose regimen, they also have some differences. The Chinese Coronavac, for example, requires a booster shot at 14 days, while the Indian was on the 28th.
The two vaccine candidates 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 patented adjuvant called Algel-IMDG.
The second method of comparison is to consider the number of antibodies developed after humans were given 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 those observed in convalescent individuals. And in the case of Pfizer and BioNTech inoculation, 100% of the individuals developed antibodies and this level was almost four times.
Both figures are well ahead of Covaxin and Coronavac.