Bharat Biotech has sought permission from India's drug regulator to conduct a phase 2/3 study of its Covid vaccine Covaxin as a booster dose among those aged two to 18 years, sources told PTI.

Presently, precaution dose of Covaxin and Covishield is administered to all those aged above 18 who have completed nine months after the second dose.

"The Hyderabad-based firm had on April 29 submitted an application to DCGI seeking permission to conduct phase 2/3 trial to evaluate the safety, reactogenicity and immunogenicity of Covaxin as a booster dose in healthy volunteers aged 2 to 18 years," a source in the know of the developments told PTI.

The study is likely to be conducted at six sites, including AIIMS Delhi and Patna.

India began administering precaution doses of vaccines to the healthcare and frontline workers and those aged 60 and above with comorbidities on January 10 this year.

The comorbidity clause was removed in March making all people aged above 60 eligible for the precaution dose of Covid vaccine.

India expanded the ambit of the precaution doses of Covid-19 vaccines and on April 10 began administering the jabs to all aged above 18 years at private vaccination centres.