Covaxin produced neutralising antibodies against the novel coronavirus – a crucial requirement for protection from Covid-19 disease.
Almost three weeks after the COVID-19 vaccine candidate from Bharat Biotech and ICMR, Covaxin, was given emergency use approval by Indian authorities, the duo has published an interim report in leading medical peer-reviewed journal Lancet today. The study reports findings from the vaccine’s adaptive Phase 1 trials in 375 healthy volunteers at 11 different trial sites across India. The vaccine was tolerated well in people between 18-55 years of age, and didn’t cause any serious adverse events.
The Covaxin candidate (also called BBV152) prompted two kinds of immune response (humoral and cell-mediated) needed for a robust natural immune response against the SARS-CoV-2 virus. The shot was also found effective against at least two different variants of the SARS-CoV-2 virus. It also produced neutralising antibody responses against SARS-CoV-2 – a promising indicator of the vaccine’s ability to control the SARS-CoV-2 infection and prevent it from escalating into COVID-19 disease.
However, the efficacy of the vaccine – which reflects the proportion of vaccinated people who are likely to have protective immunity to COVID-19 disease – is still under study in ongoing Phase 3 trials in 23,000 healthy volunteers.
Vaccination dose and schedule
Researchers also reported assessing different schedules for the first and booster doses – an ‘accelerated’ schedule (with vaccination and booster given 2 weeks apart), or a routine schedule (vaccination and booster given 4 weeks apart). A routine schedule, with two different doses (3 μg and 6 μg of BBV152) is being evaluated in the Phase 2 trial.
The most common adverse events that volunteers reported after the shot was pain at the injection site, followed by headache, fatigue, and fever. Overall, the side effects including those near the injection site (e.g. redness and swelling) and others that were system-wide (e.g. fever) were experienced by 1 in 5 or 1 in 6 people that were given the vaccine. These side effects, researchers said in the study, were much lower than for other SARS-CoV-2 vaccine candidates.
One serious adverse event that was reported in a volunteer given the higher (6 μg dose) of the vaccine, was found to be unrelated to the vaccination. The volunteer test positive for SARS-CoV-2 within a week from the date of vaccination, by when the “protective immune response” of the vaccine will not have kicked in, the study said.
After Serum Institute of India and Pfizer, Bharat Biotech is the third company to apply for emergency use approval of its vaccine candidate Covaxin. The Central Drugs Standard Control Organisation (CDSCO) recommended EUA for the experimental shot on 2 January, and grated on 3 January by DCGI.
Bharat Biotech had submitted data compiled from the Phase 1 and Phase 2 trials to medrXiv, a pre-print non-peer reviewed research repository, in December 2020. Covaxin is still under investigation in a Phase 3 human trials, consisting of 23,000 participants, to better understand the efficacy and immune responses in a large sample size.
There has been much criticism about Covaxin being authorised for emergency use without any efficacy data to back up the decision. However, Bharat Biotech is the only vaccine maker in India till date to publish data from its clinical trial in a peer-reviewed journal.
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