COVID-19 vaccines have proven to be astonishingly effective, with offerings from Pfizer, Moderna, and Johnson & Johnson at the forefront of preventing the severity of the disease, and even death.

These vaccines are intramuscular, or those that are injected into the muscle tissue to induce the creation of antibodies that circulate in the blood throughout the body, safeguarding the most vital organs, creating what is termed as systemic immunity. This immune response then defends the body from illness and death, but this response only develops after the virus has entered our bodies.

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While these vaccines' efficacy in protecting us from COVID-19 is truly impressive, the SARS-Cov-2 virus still can invade our bodies in a way unprotected by vaccines: the nose and mouth. These two entry points and their ability to spread the virus are the reasons behind our mask mandates. Face masks hamper the transmission of aerosol viruses, preventing the wearers and the people surrounding them from getting infected.

Intranasal COVID-19 Vaccine Needed

But, what if an intranasal vaccine was available?

Spayed up the nose, the vaccine would pass through the upper respiratory tract, pushing the body to produce protective antibodies in that area in the body. Once it does its job, the immune response would counteract the virus as it tries to enter the body and ensure no live virus spreads out when we cough, sneeze or exhale.

While initial efforts to offer mucosal immunity seem encouraging, pharmaceuticals are just in the first stage of clinical trials, and an actual COVID-19 nasal vaccine would be available in the market at least a year away.

(Photo: Wikimedia Commons)

Current vaccines attain systemic immunity by enabling the production of antibodies called immunoglobulin G or IgG and killer T cells. These are really effective in fighting the virus before they destroy our most important body organs.

To prevent the virus from entering the body in the first place, scientists need to focus on the mucosal system. Moist tissue lining in the mouth and nose form a part of the mucosal system, which extends to the gastrointestinal and reproductive tracts. In this area, a different type of antibodies emerges from the mucosa to fight viruses. These antibodies are called Immunoglobulin A or igA, which the mucosa releases to neutralize the virus.

If a COVID-19 vaccine can make a potent mucosal immune response, our bodies can be better protected against the virus before it damages our key organs, such as the lungs and heart. And, igA antibodies have been proven stronger against the SARS-CoV-2 virus than the igG antibodies, a study (titled Enhanced SARS-CoV-2 neutralization by dimeric IgA) published in Science Transactional Medicine said. Intranasal vaccine proponents are confident that enhancing secretory igA through the mouth and nose would level up the fortification provided by current vaccines.

COVID-19 Vaccine in Nasal Sprays

For our bodies to produce secretory igA antibodies needed to combat an incoming virus, scientists believe that a vaccine must be applied along the natural route of infection. This would mean administering it in the form of a nasal spray and have it travel through the mucosa.

Current COVID-19 vaccine shots apparently do not elicit an effective antibody response in the mucosa, say immunologists. People naturally infected with COVID-19 seem to create a mucosal immune response early, but for those who rely on such vaccines to develop their immunity, intranasal vaccines could offer a necessary igA supplement to their systemic immunity.

At present, five intranasal vaccine candidates are presently undergoing clinical trials, the World Health Organization said. Altimmune is the only US company offering an intranasal vaccine in clinical trials.

Recent studies show that Pfizer and Moderna vaccines may decrease viral load and asymptomatic transmission. Research from the US Centers for Disease Control and Prevention reveals that health care workers saw a 90 percent decrease in COVID-19 transmission rates after getting fully vaccinated with its approved mRNA vaccines.

These existing vaccines, however, haven't offered solid proof that it could completely block the transmission. Immunologists say this is because transmission can emanate from various parts of the respiratory tract for different individuals. Some of these individuals, vaccinated or not, could transmit the virus if they are in close contact with other people.

These scientists believe that this transmission stems from viruses existing in the nose. Other individuals, who are called "superspreaders," may carry and transmit aerosols of a highly infectious virus from the nose or lungs, or both. Intramuscular vaccines can counteract the virus in the lungs, but without mucosal immunity through an intranasal vaccine, scientists say there is no way to fully block the viral transmission from the nose.

Mucosal Immunity Ideal in Neutralizing New COVID-19 Variants

With over 175 million doses of vaccines administered in the US, efforts are ongoing in the scientific community to block transmission, which is essentially significant in dealing with emerging viral variants. After its intrusion in the body, the genetic mutations in the virus may help it become more infectious or successful at eluding immune responses.

As a result, new versions of the virus replicates and become new variants. However, if the virus is unable to break through the mucosal and systemic immune responses, it won't be able to stay and replicate in the nasal passages and the body. And if this transmission is obstructed, it becomes difficult for the new variants to spread.

There are concerns, however, about how well an intranasal vaccine could mount a lasting immune response. Scientists say mucosal immunity must contend with our microbiota and everything we eat and inhale. As such, the mucosal immunity may diminish more swiftly than the systemic immune response.

With COVID-19 expected to become a seasonal illness, people with a systemic immune response, an intranasal vaccine could act as a booster to bolster their mucosal immunity and safeguard against variants.

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