Biological E has submitted an application to India's drug regulator seeking emergency use authorisation for its Covid vaccine Corbevax as a booster dose in adults fully vaccinated with Covishield or Covaxin, sources said on Wednesday.

The Drugs Controller General Of India (DCGI) had already approved Corbevax, India's first indigenously developed RBD protein subunit vaccine, for restricted use in emergency situations for those aged five and above. Currently, it is being used to inoculate children in the age group of 12 to 14 years.

According to the EUA application submitted to DCGI, Biological E in a phase-3 placebo-controlled clinical study, based on the drug regulator's nod, has evaluated the safety and immunogenicity of Corbevax as a single-dose booster in Covid-negative adults fully vaccinated with either Covishield or Covaxin.

The study was conducted on 416 subjects aged 18 to 80 who were vaccinated with two doses of either Covaxin or Covishield with the last jab administered at least six months prior to giving the booster dose of Corbevax. "The results showed a significant boost in immunogenicity in terms of neutralizing antibodies after 28 days when compared with placebo cohort in both Covishield and Covaxin arms.

"The safety profile of Corbevax was found similar to that of the earlier clinical trials," an official source told PTI quoting the Hyderabad-based firm as having mentioned in the EUA application. The firm said, "We are now submitting the marketing authorization application for grant of permission Corbevax for restricted use in an emergency situation as a booster dose at six months after completion of primary immunization with two doses of Covishield or Covaxin in individuals aged 18 years and above."

As of now, the precaution dose is of the same COVID-19?vaccine used for administering the first and second doses. India began administering precaution doses of Covid vaccines?to healthcare and frontline workers and those aged 60 and above with comorbidities from January 10.?The comorbidity clause was removed in March, making all people aged above 60 years eligible for the precaution dose of Covid vaccine. India on April 10 began administering precaution doses of COVID-19 vaccines to all aged above 18 years at private vaccination centres. All those above the age of 18 who have completed nine months after the administration of the second dose are eligible for the precaution dose.

(With PTI inputs)