BHARAT BIOTECH’S indigenous Covid vaccine candidate Covaxin, which is currently in late-stage clinical trials, triggered both humoral and cell-mediated immune responses and was well-tolerated with no serious adverse events in its Phase 2 trials, according to a research paper published by the Hyderabad-based firm, which is yet to be peer-reviewed.
The researchers, however, said that the efficacy of its vaccine candidate can be evaluated in the large Phase 3 clinical trials.
Significantly, the subject expert panel, which is examining Bharat Biotech’s application for emergency use authorisation of its vaccine candidate, has asked it to present the safety and efficacy data from the ongoing Phase 3 clinical trials for further consideration. The firm has only submitted interim safety and immunogenicity data of its Phase 1 and 2 trials in the country while seeking emergency use authorisation of its vaccine.
Phase 2 of the clinical trials was conducted across nine hospitals in nine states. “…this study was conducted with participants from diverse geographic locations, enrolling 380 participants across nine hospitals. The study enrolled participants with a wide range of ages and found no differences in immune responses across age groups,” the researchers said.
A human body has two mechanisms of immunity response. First is the humoral immune response, also called antibody-mediated immunity. However, when a virus enters a cell, and it can no longer be detected by antibody-mediated immunity, there is a possibility that cell-mediated immune response takes over to kill the virus. Cellular immunity occurs inside the infected cell – and mediated by T lymphocytes.
“In the Phase 2 trial, BBV152 led to tolerable safety outcomes and enhanced humoral and cell-mediated immune responses,” the researchers said in the paper.
They said the vaccine-induced immune response was comparable to those observed in convalescent serum collected from patients who had recovered from Covid-19. “…seroconversion rates of neutralising antibodies on day 56 were 92·9% and 98·3% in the 3 µg and 6 µg with…groups, respectively,” the paper said.
“It is hypothesised that the humoral and cell-mediated responses reported in this study may persist until at least 6-12 months after the second vaccination dose,” the researchers concluded on immune response.
During the trial, the solicited local adverse events included pain at the injection site and swelling, and systemic adverse events included fever, fatigue, body aches, headache, nausea and diarrhoea. The researchers said that “no serious adverse events were reported in this study”.
“After both doses, the most common solicited adverse events were injection site pain, at 2·6% and 3·2 % in the 3 µg and 6 µg …groups, respectively. The majority of the adverse events were mild and resolved within 24 hours of onset,” the researchers said.
They said a total of 6 out of 21 unsolicited adverse events were reported to be related to the vaccine. “No serious adverse events were reported until day 56,” they said. “The most common adverse event was pain at the injection site, followed by headache, fatigue, and fever. No severe or life-threatening (Grade 4 and 5) solicited adverse events were reported.”
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