NEW DELHI: A booster dose of anti-coronavirus vaccine Covaxin will enhance its efficacy against the Delta variant of the SARS-CoV-2 virus, also known as Covid-19, and even protect against the Omicron variants BA.1.1 and BA.2, a new study has revealed.
The National Institute of Virology, the apex virology laboratory of the Indian Council of Medical Research (ICMR), conducted the study on hamsters to arrive at the conclusion.
Covaxin is one of the two anti-Covid vaccines used to vaccinate people under the national coronavirus immunisation programme that began in January 2021.
The inactivated whole virion vaccine was co-developed by Hyderabad-based Bharat Biotech and the ICMR.
The researchers compared the efficacy of Covaxin after the second and third doses against the Delta variant that hit India during the second wave, and also studied its efficacy against the Omicron variants in a Syrian hamster model.
According to the paper, researchers studied the antibody response, clinical observations, viral load reduction and lung disease severity.
“Protective response in terms of the reduction in lung viral load and lung lesions were observed in both the second as well as third dose of Covaxin immunised group when compared to placebo group following the Delta variant challenge. In spite of the comparable neutralising antibody response against the homologous vaccine strain in both the Dose 2 and Dose 3, considerable reduction in the lung disease severity was observed in the third dose immunised group post Delta variant challenge, indicating the involvement of cell mediated immune response also in protection,” the paper stated.
{{/usCountry}}“Protective response in terms of the reduction in lung viral load and lung lesions were observed in both the second as well as third dose of Covaxin immunised group when compared to placebo group following the Delta variant challenge. In spite of the comparable neutralising antibody response against the homologous vaccine strain in both the Dose 2 and Dose 3, considerable reduction in the lung disease severity was observed in the third dose immunised group post Delta variant challenge, indicating the involvement of cell mediated immune response also in protection,” the paper stated.
{{/usCountry}}“In the vaccine efficacy study against the Omicron variants BA.1 and BA.2, lesser virus shedding, lung viral load and lung disease severity were observed in the immunised groups in comparison to the placebo groups,” it further said.
Earlier, Bharat Biotech made public the results of Phase 2, double-blind, randomised controlled Covaxin trials that demonstrated long-term safety with no serious adverse events within six months after receiving the second shot.
The results also showed good cell-mediated response.
“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…,” the company said in a statement in January.
“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,” it added.