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NEW DELHI : Only one of the nearly 300 participants who were part of the vaccine arms of Bharat Biotech International Ltd’s phase 1 study of Covaxin showed serious side-effect during the trial, a pre-print of the interim analysis of the trial showed. The side-effect was deemed as not related to the vaccine, showing that the shots were safe to use.

“The vaccine was well tolerated in all dose groups with no vaccine-related serious adverse events. Robust humoral and cell-mediated responses were observed in the Algel-IMDG recipients," the interim analysis, which has not been peer-reviewed yet, showed.

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The phase 1 trial for safety and immunogenicity of Covaxin was carried out among 375 participants, with 75 placed in the placebo arm, and 100 each put in three vaccine groups of different doses and combinations of antigen and adjuvant.

While an antigen is the main component of the vaccine, an adjuvant is a compound used to boost the immune response to produce more antibodies and longer-lasting immunity, thus minimizing the dose of antigen needed.

Two doses of the vaccine and the placebo were given 14 days apart during the phase 1 trial, and the interim analysis was conducted 42 days after the first dose.

Among the participants, one serious adverse event was reported in a group five days after receiving the first shot of the vaccine. While it was initially reported as a “solicited adverse event", it was later classified as “not causally associated with the vaccine".

“We recognize that this study was conducted during a time of high ongoing degree of covid-19 circulation, as evidenced by 8% of the participants in the placebo arm seroconverting with antibodies to SARS-CoV-2 (at day 28)," the researchers said in the study.

Even in terms of immunogenicity, about 82-92% of the participants in the three vaccine groups had antibodies against the novel coronavirus, SARS-COV2, after the second dose. However, it has to be noted that the immunogenicity data is interim and is traditionally conducted in a phase 2 study. Results for phase 2 have not been disclosed.

Bharat Biotech’s Covaxin is currently in the third phase of its clinical trial, comprising of 26,000 participants, to determine the efficacy of the vaccine.

“It’s a well-conducted study. Their results are very clean. I did not find anything in the study that would concern me, and all the results that they have, which is safety and reactogenicity (side-effects) as the primary objective and immunogenicity as a secondary objective look pretty good," Davinder Gill, a vaccine expert based in Massachusetts, US, said.

Gill, however, cautioned against making a comparison of Covaxin with other vaccines as it is premature considering that it is an interim data, and the processes used to obtain the values for different vaccines may have been different.

While Bharat Biotech was administering its two doses of vaccines during the trial 14 days apart in the first phase of the trials, it later shifted to 28 days. In the ongoing third phase, Bharat Biotech is giving the vaccines 28 days apart.

“I think the change in timing of the second dose is not a concern. I would have been concerned that 14 days would have been too short as the immune system requires enough of a gap to get a better booster response from a second dose. So 28 days seems reasonable," Gill said.

Bharat Biotech had submitted its application for emergency licensure from the Drug Controller General of India V.G. Somani earlier this month based on its phase 1 and 2 clinical trials, which was on safety and immunogenicity. However, an independent subject expert committee appointed by the DCGI last week deferred its decision to recommend emergency licensure, asking the company to submit phase 3 data on efficacy when available.

Bharat Biotech was initially planning to launch Covaxin by June next year, unless the government decides to give the vaccine an emergency use authorization before that, based on data from earlier phases of clinical trials. The company is spending around 150 crore on the phase 3 trials and another 120-150 crore in setting up a new facility that will be operational by December.

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