ICMR study finds improved efficacy after Covaxin booster dose

A study by ICMR and Bharat Biotech has found out that Covaxin administration as a booster dose increases the effectiveness of the vaccine against the delta variant of COVID-19 and provides protection against Omicron variants BA.1.1 and BA.2.

The study was administered in a Syrian hamster model (animal model to study human-associated diseases) whereby they studied the effectiveness of two and three-dose of Bharat Biotech's Covaxin against Delta variant and Omicron variants of the virus.

The study also looked at the antibody response, clinical observations, viral load reduction and lung disease severity after virus challenge.

These findings have been published on bioRxiv, a pre-print server, on Tuesday and have not been subjected to peer review.

"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 neutralising 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 immunised animals indicating the vaccine efficacy against Delta variant," the study by Indian Council of Medical Research and Bharat Biotech said.

In the second study, which evaluated the protective response against Omicron variants, i.e. BA.1 and BA.2, after three-dose vaccinations were administered, reduced virus shedding, lung viral load, and lung disease severity were observed in the immunization groups when compared to the placebo groups, according to the New Indian Express.

"The evidence from the present study shows that Covaxin booster immunisation tends to broaden the protective immune response and reduces disease severity against the Delta and Omicron variant infection," it further said.