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Explained: What's Bharat Biotech's Nasal Covid Vaccine iNCOVACC, Can It Be Taken As 2nd Booster?

India has approved one booster dose of coronavirus vaccine for those who have had two regular doses. There is no provision for second booster dose.

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A nasal vaccine is one given through nose (Representative photo)
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The Bharat Biotech's nasal coronavirus vaccine iNCOVACC will hit the shelves in January. 

After Bharat Biotech released details over price and availability, the Union government said iNCOVACC nasal vaccine cannot be taken if you have already taken a booster dose. 

The clarification comes at a time when the Union government has emphasised on coronavirus vaccines' booster doses, formally called precaution doses. 

Here we explain what are nasal vaccine, how Bharat Biotech's iNCOVACC works, and what the government has said about its use as booster dose.

What's a nasal vaccine?

A nasal vaccine is one that's administered via nose. It can he inhaled as a spray or dropped into your nose as drops via a dropper.

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One benefit expected from nasal vaccines is that it fortifies nose against coronavirus. It is believed to be helpful as nose is usually the place from where SARS-CoV-2, the virus causing Covid-19 disease, first enters the human body. 

"Intranasal vaccines are best suited to protect against pathogens that enter through the nose, like the flu or the coronavirus. By mimicking the first step of natural exposure to an airborne pathogen, these vaccines help train a person’s immune system at the potential place of infection," explained Outlook in an earlier article.

Though vaccines's main function is to prevent deaths and severe disease, there is also some evidence that nasal vaccines can also be relatively better at preventing transmissiom. 

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Outlook earlier noted, "As these vaccines are put directly into the nose and mouth, they might prevent the virus from taking hold in the mucus membranes and mucosal tissue. If this works well, this would check the airborne transmission of coronavirus."

“I don't want to overstate it because no one has proven their efficacy, but their potential is extremely high," said Dr Paul Spearman of America’s Cincinnati Children's Hospital, who is developing a nasal vaccine.

It will provide longer-lasting protection than current vaccines, which have required booster doses to remain effective, said Spearman as per USA Today

What's Bharat Biotech's iNCOVACC, how it works?

The iNCOVACC is a nasal vaccine developed by Bharat Biotech. The company earlier also made Covaxin, which is one of the two main vaccines used in India, with the other being Covishield manufactured by the Serum Institute of India (SII).

Bharat Biotech on Tuesday said that the vaccine will be first rolled out for booster doses. It added that the vaccine is world's first nasal vaccine to be approved for a two-dose regimen.

The iNCOVACC is a viral vector vaccine, which means that it inserts a part of the coronavirus through a medium into a person's body to train the immune system.

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The US Centers for Disease Control and Prevention (US CDC) explains: "The vector virus in the vaccine is not the virus that causes Covid-19, but a different, harmless virus. It enters the muscle cells and uses the cells’ machinery to produce a harmless piece of what is called a spike protein

"Next, our cells display the spike protein on their surface. Our immune system recognises that the spike protein does not belong there. This triggers our immune system to produce antibodies and activate other immune cells to fight off what it is an infection...At the end of the immune building process, our bodies have learned how to help protect against future infection with the virus that causes Covid-19."

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The iNCOVACC uses a chimpanzee adenovirus as a vector. 

India Today reported that iNCOVACC was developed by Bharat Biotech in collaboration with Washington University, USA.

"The vaccine was developed in partnership with Washington University, St Louis, which had designed and developed the recombinant adenoviral vectored construct and evaluated in preclinical studies for efficacy. Product development related to preclinical safety evaluation, large-scale manufacturing scale up, formulation and delivery device development, including human clinical trials, were conducted by Bharat Biotech," reported India Today.

Bharat Biotech says the iNCOVACC vaccine generates broad immunity and also prevents transmission.

"An intranasal vaccine stimulates a broad immune response – neutralizing IgG, mucosal IgA, and T cell responses. Immune responses at the site of infection (in the nasal mucosa) – essential for blocking both infection and transmission of Covid-19," says Bharat Biotech on its website.

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Government's clarification on iNCOVACC's booster use

The Union government on Tuesday said that iNCOVACC will not be administered to people who have already had one booster dose, formally dubbed precaution dose.

A booster dose is an additional dose beyond the usual two-dose regime given to people. Since vaccine-derived immunity might wane after a period of time, the purpose of the booster dose is to update the person's immunity. In India, there is provision for only one booster dose. In the United States, there is a provision of two boosters (a total of four doses) and an additional dose for immunocompromised persons (total five doses). 

However, there is no such provision in India, which made the government clarify that iNCOVACC as booster will only be given to people who have not yet received a booster dose.

"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," said NK Arora, Chairman of National Technical Advisory Group on Immunisation (NTAGI) to NDTV in an interview.

Arora further said, "As part of the programme, no. CoWIN will not accept a fourth dose."

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Arora also explained the reasoning for not going ahead with the fourth dose.

He told NDTV, "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."

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India's focus on boosters

The Union government has emphasised the administration of booster doses in the light rising Covid-19 cases in China and other countries, such as the United States, which have led to concerns over a potential Covid-19 surge in India.

Last week, Prime Minister Narendra Modi said that elderly and vulnerable people should be encouraged to take boosters.

Separately, NITI Aayog member (Health) Dr VK Paul flagged the very low booster dose coverage among Indians. He said only 27-28 per cent Indians have taken the third booster dose of coronavirus vaccine, dubbed by the government as a precaution dose.

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