Nasal vaccine is recommended as first booster: Dr NK Arora
Nasal vaccine is recommended as a first booster and can not be administered after one has taken the booster or the precaution dose, COVID Task Force Chief Dr NK Arora told NDTV days after nasal vaccine, iNCOVACC, was introduced on the CoWIN platform.
Dr Arora is the Chairman of the COVID Working Group of NTAGI.
"CoWIN will not accept a fourth dose"
To the question on whether a person can take the nasal vaccine after three doses, Dr Arora says, "as part of the programme, no CoWIN will not accept a fourth dose."
"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 told the media.
How does a nasal vaccine work?
Nasal vaccine is delivered through the nose or mouth. It is expected to work on the mucosal lining. Hence nasal vaccine prompts an immune response at the entry points of the virus which is mostly nose and mouth.
It can prevent infection right there itself and can also cut down the chances of spread of the virus.
It is being referred to as sterilizing immunity.
Many studies have found that nasal delivery of vaccines creates a strong immune response.
Which nasal vaccine is available in India?
Currently, iNCOVACC, a novel adenovirus vectored, intranasal vaccine, has been approved. The vaccine has been manufactured by Bharat Biotech.
"Mice, Hamsters and macaques were immunized with a single dose of ChAd-SARS-CoV-2-S conferred superior protection against SARS-CoV-2 challenge. Post-challenge with SARS-CoV-2, viral clearance was observed in both lower and upper airways in all these animal models," Bharat Biotech says in an official statement.
What is the composition of the nasal vaccine?
0.5 ml of this nasal vaccine contains NLT 5X10 particles per mL ChAd36-SARS-CoV-S COVID-19 virus (recombinant) including excipients such as Tris (pH 7.4), Sodium Chloride, Magnesium Chloride, Glycerol, Polysorbate- 80.
Are they better than injectable vaccines?
Nasal vaccines have a proven benefit over injectable vaccines. In the third phase of clinical trial which was done on 3,000 participants, iNCOVACC showed good immunity with 2 doses given 4 weeks apart.
The intramucosal vaccine works on the respiratory tract. These localized cells “act as sentinels at the site of infection”, Benjamin Goldman-Israelow, a physician-scientist at Yale School of Medicine in New Haven, Connecticut told Nature. “They can act much more quickly.”
What are the nasal vaccines available outside of India
Apart from India, China has also approved a needle free vaccine. China's nasal vaccine has been developed by CanSino Biologics in Tianjin. It is used as a booster dose in China.
In India, the nasal vaccine is approved as a two dose primary vaccine instead of booster.