A booster dose of Covaxin administered six months after the two dose primary vaccination has shown elevated immune responses against SARS-CoV-2 variants of concern including Omicron and protection from severe disease, a study by ICMR and Bharat Biotech has found.

The emergence of Omicron with at least 30 mutations within most vaccines' target region -- the spike protein -- raised an alarm about its immune escape from vaccine-induced neutralising antibodies, thereby leading to increased transmissibility and causing breakthrough and reinfection, senior scientist at the National Institute of Virology (NIV) in Pune, Dr Pragya Yadav, told PTI.

Additionally, reports of waning of antibody responses against the emerging variants of concern (VoCs) of virus for other approved vaccines have raised concern globally, she said.

As a part of the study the antibody responses in sera of 51 participants who received two doses of Covaxin collected six months post second dose and 28 days after receiving a third (booster) dose (given on day 215th post second dose) and its impact against the Omicron VoC was evaluated.

The study by the Indian Council of Medical Research (ICMR) and Covaxin manufacturer Bharat Biotech was conducted in January and the findings were published in the Journal of Travel Medicine on March 24.

"The antibody response was higher for participants administered with booster doses for B.1 and the VoCs -- Delta, Beta and Omicron variants,"? Dr Gajanan Sakpal, another senior scientist at the NIV, said.

This indicates that the booster dose of Covaxin robustly triggered neutralising antibody responses and efficiently neutralised the multiple variants of SARS-CoV-2, Sakpal said.

"We conclude that the neutralising antibody responses were significantly elevated after third dose of BBV152/Covaxin against the homologous B.1 (19.11 fold) and other heterologous strains (16.51 fold), Beta (14.70 fold) and Omicron (18.53 fold) VoCs, providing assurance of a protective immune response of booster in recipients," the study stated.?

"The data emphasises the need for speedup of the booster doses to individuals for dealing with emerging VoCs and its outcome to protect against death, severity and hospitalisation burden," it stated.

The government on Friday announced that precaution dose of COVID-19 vaccines will be available to all aged above 18 years at private vaccination centres from April 10.?

Those above the age of 18 who have completed nine months after the administration of the second dose will be eligible for the precaution dose, it has said.