Bharat Biotech, which is one of the leaders in the race to develop a coronavirus vaccine in India, released new data from the 1/2 phase 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 the key indicators and their comparison with other candidates.
The Bharat Biotech coronavirus vaccine candidate, developed jointly with the Indian Council for Medical Research (ICMR), passed the two crucial tests in the clinical trials, which proved to be safe and elicited an immune response, according to the first analyzes published this Wednesday.
Phase 1/2 data showed that neutralizing antibody levels in those receiving the vaccine (called Covaxin) were similar to those recovered from a natural infection. This level was at a maximum at 42 days after the second dose, with a decrease observed at 104 days.
Among all participants in the initial phase who received the vaccine, 98.3% were “seroconverted” (i.e., developed an antibody response).
But how do these figures compare to other major vaccine candidates whose data have been published?
The comparison can be done in two ways: by drawing parallels with other candidates who use the same method to form a person’s immunity or by comparing some of the parameters with the main candidates already approved.
Bharat Biotech’s Coovaxine is based on an inactivated virus and, for the first method of comparison, there are four others in final phase trials that can be compared. All four are being developed by Chinese companies, but only one, Coronavac de Sinovac, has conducted an analysis that can be collected to compare them.
At first, it seems that the Indian candidate may be comparable or even slightly better than his rival in some parameters. When given the two doses of Covaxin, 98.4% of them developed antibodies compared between day 56 and 100% on day 28 after the two-dose regimen in the Coronavac trial, according to the data from the phase 2 trial published by both.
The difference was most pronounced in determining the level of antibody response. In the case of Covaxin, volunteers showed levels similar to those who had a natural Sars-Cov-2 infection and recovered. But in the case of Coronavac, that level was about a third of what was seen in recovered individuals.
Of course, there could still be some variations in the test methods used by the researchers and the studies were conducted separately, in different populations, which do not provide 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 compare vaccine performance smoothly.
Sinovac and Bharat Biotech judged their vaccines by these parameters, while the other three candidates for the inactivated virus platform in end-stage trials (two of them are from Sinopharm and the third from the Chinese Academy of Medical Sciences) have not compared antibody levels with convalescent patients. .
While the Indian and Chinese candidates have a platform overlay and both use a two-dose regimen, they also have some differences. The Chinese Coronavac, for example, requires a reinforcement shot at 14 days while the Indian was at 28 days.
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 proprietary adjuvant called Algel-IMDG.
The second method of comparison is to take into account the number of antibodies developed after people received the Modern and Pfizer-BioNTech vaccines.
In the case of Moderna, 100% of people developed antibodies and the levels exceeded twice the levels observed in convalescent individuals. In the case of the inoculation of Pfizer and BioNTech, 100% of the individuals developed antibodies and this level was about four times.
Both figures are well ahead of Covaxin and Coronavac.