India's nasal vaccine cannot be administered to those who have taken a precaution or booster dose, the head of the country's vaccine task force told NDTV on Tuesday in an exclusive interview.
The nasal vaccine, iNCOVACC, was introduced on the CoWIN platform last week.
"It (nasal vaccine) is recommended as the first booster. For example, if a person has already received a precaution dose, it is not recommended for that person. It is for those who have not yet taken a precaution dose," Dr NK Arora, who has been closely involved with the rollout of vaccines from the onset of the pandemic, told NDTV.
Dr Arora is the Chairman of the Covid Working Group of NTAGI, short for the National Technical Advisory Group on Immunisation, which works on introduction of new vaccines and strengthening the universal immunisation programme.
"As part of the programme, no. CoWIN will not accept a fourth dose," he told NDTV when asked whether a person who has taken a booster dose can take the nasal vaccine.
"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.
The nasal vaccine provides a very interesting way of immunisation, he said.
"...The entry point (of the vaccine) is the respiratory system - nose and mouth where the immune system builds roadblocks so that the virus is not allowed to enter so easily into the system...This is going to help in fighting not just Covid, for all the respiratory viruses and infection this is a platform that is going to be very useful in fighting them," Dr Arora said.
The needle-free vaccine received approval of the Drugs Controller General of India in November for restricted use in an emergency situation.
Anybody above the age of 18 years can get the nasal vaccine. "It's very simple. Four drops in each nostril, total of 0.5 ml is to be administered. That's it. And it has very little adverse events except some nasal blockage for a short while, otherwise whatever the data is, it is an extremely safe vaccine," he said.
"For this vaccine, as with any other vaccine, we need to wait for 15 to 30 minutes in case if there is a reaction it can be taken care of immediately, although there were no reports in whatever data we have seen," he said.
On whether people would need to take booster after booster doses of the nasal vaccine, Dr Arora said, "The scientific answer is at the moment there is no evidence that further vaccines will be required or not required. Even in countries where people have taken three, four or five doses of vaccine, particularly these mRNA vaccines in North American and Europe, but they continue to suffer from infection."
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