Updated: January 9, 2022 3:40:51 am
A phase 2, double-blind, randomised controlled trial demonstrated long-term safety of Covaxin vaccine with no serious adverse events, the company said.
Six months after the second Covaxin dose, a study using the vaccine as a booster dose has detected neutralising, T and B cell responses. This suggests good immune memory responses and long-term protection from severe disease, an official statement from Bharat Biotech said.
Nearly 90% of recipients had a detectable neutralising antibody response against the wild-type strain (six months after the second dose).
Neutralisation titers against wild-type and Delta variants were five times higher than after a two-dose schedule. Similar increases in neutralising antibodies against Alpha, Beta, Delta plus were also observed.
The booster dose led to a pronounced increase in CD4+ T- and CD8+ T cell response. This may allow Covaxin to confer long-term protective efficacy against severe SARS-CoV-2.
The frequency of adverse events was lower than vaccines from other manufacturing platforms. Covaxin is the first vaccine (in India) to report safety and immunogenicity results from a booster clinical trial.
The analysis showed that six months after a two-dose BBV152 vaccination series, cell-mediated immunity and neutralising antibodies to both homologous (D614G) and heterologous strains (Alpha, Beta, Delta, and Delta plus) persisted above baseline, although the magnitude of the responses had declined.
Furthermore, neutralising antibodies against homologous and heterologous SARS-CoV-2 variants increased 19 to 265 fold after a third vaccination. Booster BBV152 vaccination is safe and may be necessary to ensure persistent immunity to prevent breakthrough infections.
Dr Krishna Ella, chairman and managing director of Bharat Biotech, said, “These trial results provide a strong foundation towards our goal to provide Covaxin as a booster dose. Our goals of developing a global vaccine against Covid-19 have been achieved. Covaxin is now indicated for adults, children, 2 dose primary and booster doses. This enables the use of Covaxin as a universal vaccine.”
“We found that the vaccine induces both memory B and T cells with a distinct CD4 and CD8 phenotype.
Further, reactogenicity after vaccine and placebo was minimal and comparable, and no serious adverse events were reported,” the statement said.
While protection against the severe disease remains high across the full six months, a decline in efficacy against symptomatic disease over time and the continued emergence of variants are expected. Based on emerging data, Bharat Biotech believes that a third dose may be beneficial to maintain the highest levels of protection.
Covaxin is formulated uniquely such that the same dosage can be administered to adults and children alike. Covaxin is a ready-to-use liquid vaccine, stored at 2 – 8°C, with 12 months shelf life and multi-dose vial policy.
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