BHARAT BIOTECH’S indigenous Covid vaccine candidate Covaxin, which is currently in late-stage clinical trials, has been found to be well-tolerated, with no vaccine-related serious adverse events, and triggered a robust immune response in its early Phase 1 clinical trial, according to a research paper published by the Hyderabad-based firm, which is yet to be peer-reviewed.
This comes even as 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 trial 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 1 of human clinical trials, in which the vaccine candidate is tested on a small group of healthy adults, reveals interim data on two important aspects. First, reactogenicity, which is the ability to produce anticipated adverse reactions like muscle pain, fever as well serious or rare adverse reaction. Second, immunogenicity or the ability to trigger an immune response.
In the Phase 1 study, which is being jointed conducted by the ICMR, the researchers have said the reactogenicity “was absent in the majority of participants, with mild events”. And on immune response, the researchers concluded that both “robust humoral and cell-mediated responses were observed”.
“…this study has several strengths. To ensure generalizability, this study was conducted with participants from diverse geographic locations and socioeconomic conditions, enrolling 375 participants across 11 hospitals. Despite the fact that enrollment occurred during a national lockdown, which led to several operational challenges, the overall participant retention rate was 97%. The sample size was intentionally large to enable the inference of meaningful conclusions regarding immunogenicity and safety,” the researchers concluded.
On the adverse events, the researchers said that the “overall incidence rate of local and systemic adverse events” was 10%-20% in all vaccine treated arms. “The majority of adverse events were mild and were resolved,” the study said. Also, one serious adverse event was reported – “which was found to be unrelated to vaccination” — the researchers said.
On safety, the researchers concluded, “After the first vaccination, local and systemic adverse events were predominantly mild or moderate in severity and resolved rapidly, without any prescribed medication. A similar trend was observed after the second vaccination.”
The study further said that pain at the injection site was the most common local adverse event. “The distribution of local and systemic AE (adverse events) was equal among the vaccine treatment groups when compared to the control arm… Biochemical, hematological, and urine parameters outside of the normal ranges had no corroborating clinical manifestations,” it said.
The study said the vaccine candidate “induced” neutralising antibody responses, and that vaccine-induced responses were “comparable to those observed in the convalescent serum collected from patients who had recovered from COVID-19”. “All three vaccine formulations resulted in robust immune responses comparable to a panel of convalescent serum,” the study said.