The administration of the third dose of Bharat Biotech’s COVID-19 vaccine Covaxin (BBV152) after six months of two-dose vaccination dramatically increased neutralising antibody responses against both homologous and heterologous strains (Alpha, Beta, Delta, Delta Plus, and Omicron) and showed increased memory B cell response in subjects in controlled clinical trials, the company announced on Wednesday. According to the company, the findings are based on a comprehensive study that demonstrated multiple benefits of Covaxin, including long-term immune response, cell mediated immunity, booster dose safety, immunogenicity against spike protein, N protein, and neutralising antibody responses against alpha, beta, delta, delta plus, and omicron variants.
The study said Covaxin-induced robust T cell responses persisted till six months, even after antibody decline. These T cell responses have been followed up to 12 months in vaccinated individuals, irrespective of receipt of third dose. T cell responses in turn help to produce B cell memory response, upon antigen re-exposure. Thus, Covaxin provides long-term immunity.
Bharat Biotech said immune responses declined at six months but increased by 40 fold in subjects who received a booster dose. Immune responses when assessed against variants of concern and persisted up to 12 months.
The study was conducted in 184 subjects, who were randomized 1:1 and received either a booster dose of BBV152 or a placebo, 6 months after the primary series of two doses. Subjects were evaluated for safety, neutralizing antibody responses against variants of concern, binding antibodies against spike protein, RBD, N proteins, and for memory T and B cell responses to demonstrate cell-mediated immunity, said the company.
Dr Krishna Ella, Chairman and Managing Director, Bharat Biotech, said, “Our team has now demonstrated that Covaxin is a multi-epitope vaccine with antibodies against spike, RBD and N proteins. Post booster dose, it has proven to neutralize antibody responses against variants of concern and long term protection through memory T and B cell responses. We have now achieved our goal of developing a safe and efficacious vaccine with long-term protection against a spectrum of variants.”
Covaxin, according to Bharat Biotech, is manufactured in such a way that the same dosage may be given to adults and children for both main and booster doses, making it a universal vaccine.
Bharat Biotech claims to have more than 50 million doses of Covaxin on hand, ready to be delivered as needed.
