New Delhi, June 15: Administration of Covaxin booster dose will enhance the vaccine effectiveness against the Delta variant of Covid-19 and give protection against two Omicron variants, suggests a study.
The study by 'bioRxiv' shows that administration of Covaxin booster dose improves vaccine effectiveness against Delta variant and gives protection against the Omicron variants BA.1.1 and BA.2. The study also examined the immunity acquired after natural infection or vaccinations against SARS-CoV-2.
Vaccine effectiveness also varies with the variant of infection, the study added.
The team of researchers compared the protective efficacy of Covaxin following the second and third dose vaccination against the Delta variant and also analysed the efficacy of Covaxin against Omicron variants in a 'Syrian hamster model'.
"The antibody response, clinical observations, viral load reduction and lung disease severity after virus challenge were studied. The protective response in terms of the reduction in lung viral load and lung lesions were observed in both the second dose as well as third doses of Covaxin immunized group when compared to placebo group following the Delta variant challenge," the research stated.
It further added, "In spite of the comparable neutralizing antibody response against the homologous vaccine strain in both the second dose and third dose immunized groups, considerable reduction in the lung disease severity was observed in the third dose immunized group post-Delta variant challenge indicating the involvement of cell-mediated immune response also in protection."
"In the vaccine efficacy study against the Omicron variants i.e., BA.1 and BA.2, lesser virus shedding, lung viral load and lung disease severity were observed in the immunized groups in comparison to the placebo groups. The present study shows that administration of COVAXIN booster dose will enhance the vaccine effectiveness against the Delta variant infection and give protection against the Omicron variants BA.1.1 and BA.2," the study concluded.
The Covaxin vaccine, manufactured by the Indian Council of Medical Research (ICMR) in collaboration with Bharat BiotechInternational Limited (BBIL), shows an interim efficacy of 81 percent in preventing Covid-19, according to phase 3 data.
Covaxin is the country's first Covid-19 vaccine developed in India. India's nationwide vaccination campaign began on January 16, 2021.