The National Technical Advisory Group on Immunisation does not have sufficient data to make a recommendation on mixing of coronavirus vaccines, the Centre told the Rajya Sabha on Tuesday.

Minister of State for Health, Bharti Pawar, made the statement in response to a question by Congress MP Anand Sharma.

Mixing vaccine doses mean that the jabs given to beneficiaries are from two different companies to generate better immune response to the disease. This can either be for a multidose regimen or for booster shots.

The United States, Canada and some European Union countries allow heterologous use of Covid-19 vaccines.

In her reply, Pawar also said that India’s drug regulator, Central Drugs Standard Control Organisation, has allowed Christian Medical College, Vellore, to conduct the phase four trial to study the immune response from mixing Covaxin and Covishield vaccine doses.

She added that the drug regulator has also granted permission to biotechnology firm Bharat Biotech to evaluate the immune response from mixing the doses of Covaxin and BBV154, the company’s intranasal Covid-19 vaccine.

Meanwhile, Dr NK Arora, member of the National Technical Advisory Group on Immunisation, told that Christian Medical College, Vellore, has submitted results of the study on mixing Covaxin and Covishield for booster doses.

“We are waiting for some additional results from them,” he said. “They will carry additional tests to measure the neutralising antibody titers.”

Neutralising antibody titers indicate whether the antibodies are able to stop the entry of a virus into a person’s body and also prevent its replication.

The Christian Medical College in Vellore had begun its clinical trial in 2021 to see the rise in antibodies if Covishield is used as a booster shot for people who got their primary vaccination with Covaxin and vice-versa.