Results from the phase 2 clinical study published in The Lancet shows that India’s first indigenously developed Covid vaccine to get the regulator’s nod for restricted emergency use — Covaxin — produced durable antibody and T-cell responses three months after vaccination.
Follow-up studies are currently on for six months and 12 months, said the authors of the study.
Moreover, the study noted that neutralising antibody titers produced in vaccinated individuals were twofold than what was observed in the phase 1 study.
The study has been authored by Raches Ella, Krishna Ella of Bharat Biotech and Nivedita Gupta, deputy director general and Balram Bhargava, director general of the Indian Council of Medical Research (ICMR), among others. The vaccine has been co-developed by Bharat Biotech and ICMR.
What’s more, the firm said that after two doses, the probability of experiencing side effects in those who received the vaccine was 10-12 per cent – almost six times lower than other vaccines which have received emergency use authorisation.
In phase 2 study, two intramuscular doses of vaccines were administered (four weeks apart) in 380 healthy children and adults.
Bharat Biotech noted, “Higher neutralising antibody titres (twofold) were observed in the phase 2 study than in phase 1 study.”
“Neutralising antibody titres were similar to a panel of convalescent serum samples,” the Lancet article said.
The most common adverse event in the phase 2 trial was pain at the injection site, followed by headache, fatigue and fever. “No severe or life-threatening solicited adverse events were reported,” it added.
The authors have further noted that serum neutralising antibodies were detected in all phase 1 participants on Day 104.
“These findings are in accordance with those of the mRNA-1273 (Moderna) vaccine, which has received emergency use authorisation,” the study said.
This study enrolled a small number of participants aged between 12–18 years and 55–65 years. The researchers said that follow-on studies are required to establish immunogenicity in children and in those above 65 years.
Covaxin has shown an interim efficacy of 81 per cent in its phase 3 clinical trial, Bharat Biotech has claimed recently.
AstraZeneca-Oxford vaccine has shown a 62 per cent efficacy with two full doses, and 90 per cent efficacy in one half and one full dose regimen. Russian vaccine Sputnik V has shown a 91.6 per cent efficacy in interim analysis data from 19,866 volunteers.
Covaxin had been approved by the country’s drug regulator Drugs Controller General of India (DCGI) for restricted use in January. The phase 3 studies, with over 25,800 subjects, were under way at that time.
The approval had created a furore among the public as well as the medical community. The government machinery had to spring into action to clear the air. Director-general of ICMR Balram Bhargava said, “While phase 3 is still ongoing, immunogenicity data generated through phase 2 clinical trial serves as a surrogate for efficacy.”
Restricted use of Covaxin in clinical trials meant that beneficiaries will have to give consent and there will be regular follow-up. Such persons will not receive the placebo.
Meanwhile, Bharat Biotech is gearing up to produce 40 million doses a month. Two BioSafety Level 3 facilities (which can deal with deadly and contagious viruses) of the company have been set up and a third one is underway. Business Standard