by HYDERABAD: A third booster shot of Covaxin, administered six months after the second dose, induced both memory B and T cells and led to a pronounced increase in T-cell responses, indicating the inactivated virus vaccine may be able to confer long-term protective efficacy against severe SARS-CoV-2, a study by Bharat Biotech and the Indian Council of Medical Research-National Institute of Virology, Pune, has shown.
The results of the study, uploaded on medRxiv that carries pre-prints of research papers before they are peer-reviewed, said the findings indicate that a booster shot of Covaxin is safe and may be necessary to ensure persistent immunity to prevent breakout infections.
Researchers of the study titled `Persistence of immunity and impact of a third (booster) dose of an inactivated SARS-CoV-2 vaccine, BBV152; a phase 2, double-blind, randomised controlled trial’, said neutralisation titers against wild-type and Delta variants of SARS-CoV-2 were five times higher than after a two-dose schedule of Covaxin and similar increases in neutralising antibodies against Alpha, Beta, Delta plus variants were observed.
According to researchers, six months after a two-dose vaccination with Covaxin, cell-mediated immunity and neutralising antibodies to both homologous (D614G) and heterologous strains (Alpha, Beta, Delta and Delta plus) persisted above the baseline but the magnitude of responses declined.
However, after a third jab, the neutralising antibodies against homologous and heterologous SARS-CoV-2 variants increased 19- to 97-fold, showing that a booster dose may be required to prevent breakthrough infections, the paper said.
Terming the results as promising, Bharat Biotech CMD Dr Krishna Ella 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 with Covaxin indicated for adults, children, 2 dose primary and booster doses. This enables the use of Covaxin as a universal vaccine.”
The company said it found the vaccine induces both memory B and T cells with a distinct CD4 and CD8 phenotype. Also, reactogenicity after vaccine and placebo was minimal and comparable with no serious adverse events being reported.
“While protection against the severe disease remains high across the full 6 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,” the company said.
The results of the study, uploaded on medRxiv that carries pre-prints of research papers before they are peer-reviewed, said the findings indicate that a booster shot of Covaxin is safe and may be necessary to ensure persistent immunity to prevent breakout infections.
Researchers of the study titled `Persistence of immunity and impact of a third (booster) dose of an inactivated SARS-CoV-2 vaccine, BBV152; a phase 2, double-blind, randomised controlled trial’, said neutralisation titers against wild-type and Delta variants of SARS-CoV-2 were five times higher than after a two-dose schedule of Covaxin and similar increases in neutralising antibodies against Alpha, Beta, Delta plus variants were observed.
According to researchers, six months after a two-dose vaccination with Covaxin, cell-mediated immunity and neutralising antibodies to both homologous (D614G) and heterologous strains (Alpha, Beta, Delta and Delta plus) persisted above the baseline but the magnitude of responses declined.
However, after a third jab, the neutralising antibodies against homologous and heterologous SARS-CoV-2 variants increased 19- to 97-fold, showing that a booster dose may be required to prevent breakthrough infections, the paper said.
Terming the results as promising, Bharat Biotech CMD Dr Krishna Ella 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 with Covaxin indicated for adults, children, 2 dose primary and booster doses. This enables the use of Covaxin as a universal vaccine.”
The company said it found the vaccine induces both memory B and T cells with a distinct CD4 and CD8 phenotype. Also, reactogenicity after vaccine and placebo was minimal and comparable with no serious adverse events being reported.
“While protection against the severe disease remains high across the full 6 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,” the company said.
