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COVID-19: What Is A Nasal Vaccine? Is It Effective Against COVID? How Is It Different From Injected Vaccine?

On Monday, PM Narendra Modi addressed the nation, highlighting the government's new steps in the fight against the COVID-19 pandemic. In his address, he also said that research on developing nasal vaccines as an alternative to vaccines are underway.

It was further mentioned that if an effective nasal vaccine is to be developed, it could boost India's anti-COVID vaccination drive. In February 2021, the use of an intranasal vaccine for COVID-19 was discussed by several experts [1].

So, what are nasal vaccines? How does it work? Does it have any side effects? Let's take a look.

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What Is Nasal Vaccine (Intranasal Vaccine)?

A nasal vaccine is given by the nose, rather than a needle through the arm. Its target is to directly deliver the dose (of medicine) to the respiratory pathway, just like a nasal spray. Reports state that last year, on 21 August, a paper was published by Washington University School of Medicine in the Cell journal. A group of scientists had developed a vaccine that targets the SARS-CoV-2 virus [2].

The nasal vaccine can be given in one dose via the nose and effectively prevent infection in mice susceptible to the novel coronavirus. The nasal vaccine is yet to be tested on nonhuman primates and humans to see if it is safe and effective in preventing COVID-19 infection. The study had also mentioned that the nasal vaccines target the initial site of infection and cause a more widespread immune response [3].

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Soumya Swaminathan, World Health Organization's (WHO) chief scientist, had said that "trials to produce nasal vaccines are underway in India, and this could be a game-changer for children" [4].


How Do Nasal Vaccines Work?

Nasal vaccines are sprayed into the nostrils, unlike the injected vaccines that are injected into the skin with the help of needles. Intranasal vaccination can be done with the help of a syringe with no needle, a nasal spray, liquid medicine or special aerosol delivery [5].

As the primary entry spot of the coronavirus is through the nose, the vaccine then intercepts the virus, causing your immune system to make proteins in your blood and in your nose to combat the virus. In addition to warding off the virus, the vaccine also prevents the virus from multiplying.

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If the virus can be stopped from entering at this point, it will not be able to get into the lungs to cause damage. Moreover, if an effective mucosal immune response is generated, it would possibly prevent the coronavirus infection from the outset.


What Are The Advantages Of Nasal Vaccines?

Some of the best reasons why nasal vaccines are better than injections are as follows [6]:

  • The nasal route has excellent potential for vaccination due to the organised immune systems of the nasal mucosa - that is, your mucus can help protect you better than your saliva [7].
  • It is non-invasive and needle-free.
  • It is easy to use and does not require trained healthcare workers.
  • It eliminates the risk of needle-associated risks such as injuries and infections.
  • It is ideally suitable for children and adults.
  • It is cost-effective and requires lesser resources as compared to the number of syringes and transportation cost needed for injected vaccines.
  • There is a lesser chance of our body rejecting the effectiveness of the vaccine, as it can be immediately absorbed by the blood vessels.
  • Scalable manufacturing, there being able to meet global demand.
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    How Are Nasal Vaccines Different From Injected Vaccines?

    • Unlike traditional vaccines, nasal vaccines target the virus present in the mucosal membranes and are given via nose rather than orally or through the arm [8].
    • Intramuscular vaccines or injected vaccines (with needles) fail to trigger such immune response from the mucosa and depend on immune cells from other parts of the body.
    • Nasal vaccines are easier to administer and may provide easy immunity.
    • Nasal vaccines not only protect against COVID-19 but also directly interacts with T-cells that exist in the nose and the throat and target the immune cells present in the mucosal membrane.

Are There Any COVID-19 Nasal Vaccines Available Now?

BBV154, an intranasal vaccine developed by Bharat Biotech, is already in the pre-clinical trial phase. Bharat Biotech, which also manufactures Covaxin, is expected to roll out ten crore doses of its nasal vaccine by the end of the year, as per the reports.

Here are some of the important points from the report published by Bharat Biotech (the findings are not peer-reviewed and are a preprint publish) [9]:

  • An intranasal vaccine stimulates a broad immune response, neutralising IgG, mucosal IgA, and T cell responses.
  • Immune responses at the site of infection (in the nasal mucosa) which is essential for blocking both infection and transmission of COVID-19.
  • The nasal route has excellent potential for vaccination due to the organised immune systems of the nasal mucosa.
  • Mice, Hamsters and macaques were immunised with a single dose of ChAd-SARS-CoV-2-S conferred superior protection against SARS-CoV-2.
  • Viral clearance was observed in both lower and upper airways after the application of the nasal vaccine.
  • Intranasal immunisation of ChAd-SARS-CoV-2-S can create an immune response in the nose, which is the point of entry for the virus and help protect against disease, infection, and transmission.
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    Note: The company report stated that the statements are made by management itself; they are considered more authentic. However, as they are predictions about the future, there is also a lot of scope for the reader to be misled. Information disclosed is subject to addition, change or deletion without notice.


Are Nasal Vaccines Effective In Treating COVID-19?

The COVID-19 virus enters the body through the mucosa and infects the cells and molecules present in the mucosal membranes. So, the use of the nasal vaccine is seen as an effective solution [10].

These intranasal vaccines can produce secretory Immunoglobulin A (IgA), which can trigger a strong immune response at the site of virus entry, i.e., the nose. IgA is said to be more efficacious in managing and destroying viruses at an early stage of infection than IgG - found in the injected vaccines [11].

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While nasal vaccines generate a robust and effective mucosal immune response, it avoids further damage of the lungs in COVID-19. Phase one trials have just started, and the vaccine has only been tested on animals.

Are There Any Disadvantages Of Nasal Vaccines?

Although the intranasal vaccines curb and neutralise viral infection in the mucosal membrane, there are certain disadvantages to it, and they are as follows [12]:

  • Antibodies produced by nasal vaccines may not be as strong in the lower respiratory tract as against the upper respiratory tract.
  • Intranasal vaccines may fail to provide effective and long-lasting immunity to the patients against the COVID-19 virus.
  • Possibilities of reversion of neuro-attenuation, meaning that the virus can attain back its ability to cause disease in the individual.

On A Final Note…

If the nasal vaccines turn out to be a success, it will make India's COVID vaccination drives more flexible. On Tuesday, Bharat Biotech received the approval for phase 1 trials and are set to begin the clinical trials by next week.