Intranasal Vaccine for COVID-19

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What is intranasal vaccine & how does it work?

• Vaccines are usually given through different routes, with the most common being injectable shots delivered into the muscles (intramuscular) or the tissue just between the skin and the muscles (subcutaneous). 
• Other routes of delivery, especially in some vaccines for infants, include administering the liquid solution orally instead of injecting. 
• In the intranasal route, the vaccine is sprayed into the nostrils and inhaled.
• Many viruses, including the coronavirus, enter the body through mucosa — wet, squishy tissues that line the nose, mouth, lungs and digestive tract triggering a unique immune response from cells and molecules there. 
• Intramuscular vaccines generally fail at eliciting this mucosal response, and instead rely on immune cells mobilised from elsewhere in the body flocking to the site of infection. 
• Experts believe an intranasal vaccine will act against the virus from the time it tries to break the body’s barrier, thereby making it more effective than the intramuscular ones in many cases.
• Generally, both the aforementioned types of vaccines trigger a response in the blood. 
• B cells, for example, would churn out antibodies including a particularly potent disease-fighter called IgG — to roam the body in search of the virus. 
• Other cells, called T cells, would either help B cells produce antibodies or seek out and destroy the infected cells.
• However, vaccines that are injected through the nose or mouth would also tap into another set of immune cells that hang around mucosal tissues. 
• The B cells that reside there can make another type of antibody, called IgA, that plays a large role in destroying the airway pathogens. 
• In addition to this, the T cells that are residing nearby will be able to memorize the pathogens that it encountered and will lifelong scout the areas where these were first encountered.
• Hence an intranasal vaccine stimulates a broad immune response – neutralizing IgG, mucosal IgA, and T cell responses.
• These vaccines aim to overcome potential difficulties with mass vaccination and reduce the cost by doing away with the need for needles and syringes.
• Intranasal vaccines are also expected to cut down on the dependence on various trained personnel to administer the vaccine, according to experts.
• The effectiveness of an intranasal vaccine was first seen in the 1960s when polio doses replaced its injected predecessor. 

Drawbacks-

• It was first noted after the rollout of the oral polio vaccines where in some cases, it still caused the disease after the weakened virus in the product mutated.
• There is very little evidence to back the effectiveness of this route of delivery so far and, save for some flu vaccines, attempts to deliver vaccines have not been successful.

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