Bharat Biotech's iNCOVACC, the nasal vaccine recently approved by the Indian government, cannot be taken as a second booster dose, according to an NDTV report.
The needle-less vaccine is recommended as the first booster, and not meant for those who have already taken a precaution dose, the report quoted Dr NK Arora, head of India's vaccine task force, as saying.
He added that "at the moment", taking a fourth dose of vaccine is of "no value", and this option is also not available on the vaccination app CoWIN.
"Let us assume you want to take another fourth dose. There is a concept what is called as 'antigen sink'. If a person is repeatedly immunised with a particular type of antigen, the body stops responding, or responds poorly.
And that is why initially mRNA vaccines are given with a gap of six months. Later on, people are taking at three-month gap. But it has not helped too much in that case. Therefore, at the moment taking a fourth dose is of no value," Dr Arora said.