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The booster dose of Covaxin has been shown to be effective against Covid-19’s Delta variant as well as Omicron variants BA.1.1 and BA.2, stated a study by Indian Council of Medical Research (ICMR) and Bharat Biotech.
The Syrian hamster model (animal model to study human-associated diseases) study was conducted on the efficacy of Covaxin against the Delta variant and Omicron variants following two and three-dose immunizations. The antibody response, clinical observations, viral load reduction and lung disease severity after virus challenge were observed.
The findings of the study have been published on bioRxiv, a preprint server and have not been peer-reviewed.
“In the Delta infection study, where we compared the protective response between the two and three-dose regimens, we could observe the advantage of the booster dose vaccination in the protection. Although the neutralizing antibody levels were comparable among the groups, lung disease severity was found more reduced after the three-dose vaccination. The virus shedding and viral organ load were considerably reduced in both the two-dose and three-dose immunized animals indicating the vaccine efficacy against the Delta variant,” the study said.
In the second study in which the protective response was assessed against Omicron variants i.e. BA.1 and BA.2, following three-dose vaccinations, lesser virus shedding, lung viral load and lung disease severity were observed in the immunized groups in comparison to the placebo groups.
“The evidence from the present study shows that Covaxin booster immunization tends to broaden the protective immune response and reduces disease severity against the Delta and Omicron variant infection,” it added.
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