Inhaling just a few drops of liquid or mist will give one?protection from Covid-19 and that is the very idea behind nasal vaccines, and they have been getting a lot of attention recently as a spray or liquid.

Not only are these vaccines going to be more comfortable, they are also believed to be more effective as they would train a person’s nose and mouth against coronavirus, which are the most common ways of entry for the virus into the human body.

Moreover, these vaccines go a step further than the first generation of vaccines currently in use. They don’t just aim to prevent death and severe disease, but also infections and transmission.?

Here is all you need to know about oral and nasal vaccines’ features, their development, the scientific evidence on them, and what they mean for the future of the vaccination as well as the pandemic.?

What are nasal vaccines?

Nasal vaccines are administered, as the name suggests, through the nose. More accurately called intranasal vaccines, these vaccines are liquids that can be given as a spray or through a dropper or syringe.?

The most common nasal vaccine is FluMist, a nasal spray that uses inactivated flu virus to protect against influenza.?

An intranasal vaccine could be a weakened live virus similar to FluMist, a nucleic acid vaccine-like mRNA coronavirus vaccine or a protein vaccine-like Hepatitis B vaccine or the CorbeVax coronavirus vaccine.

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.?

Scientists have shown that the first immune response in the respiratory tract after a person is exposed to an airborne virus can influence how sick a person gets.?

So in theory, intranasal vaccines could provide better protection than vaccines given through a shot in the arm.

How do oral and nasal vaccines differ from injections? ?

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, as per Dr Spearman, quoted in USA Today.?

When you get a Covid-19 shot in your arm, the vaccine triggers a strong immune response in the cells near where you got the shot.?It also causes your immune system to produce some coronavirus-specific antibodies and other immune cells in other locations throughout your body.

When the coronavirus begins infecting cells in a person’s respiratory tract, the immune cells nearby will start mounting a defense.?Your body will also send anti-viral immune cells and antibodies from other locations to the site of infection.?

But by the time enough coronavirus-specific immune cells gather around the infection site to stop the virus from replicating, the virus has likely already begun to spread throughout the body, making it difficult for the immune system to keep up.

Nasal vaccines mimic the virus in order to prepare the immune system against a virus, just like any other vaccine.?But importantly, they mimic the process of infection, too, and boost protective response within the mucosal immune system of the nose and throat.?

In simple terms, intranasal vaccines are like knowing there is going to be a break-in and putting your guards in the right location before the trouble even starts.

The science bears this idea out. In a head-to-head comparison, AstraZeneca’s Covid-19 vaccine provided greater protection in hamsters that were vaccinated intranasally compared to those vaccinated intramuscularly.

The next generation of vaccines –oral and nasal vaccines– are being aimed at preventing the infection and its transmission to others as well.?Finally, intranasal vaccines are painless, noninvasive and do not require specialised training to use.

What’s known of their effectiveness?

An oral coronavirus being developed in the United States not only protects against the disease, but also reduces the airborne spread of the virus in the surroundings, according to an animal study published in Science Translational Medicine.?

The PTI reported that the researchers from the biotech company Vaxart and Lovelace Biomedical Research Institute found that their oral vaccine increased production of immunoglobulin A –the immune system's first line of defence against pathogens– in the nose and lungs.

The researchers added that these mucosal ports of entry are then protected, making it less likely that those who are vaccinated with their oral vaccine would transmit the?virus during a sneeze or cough.

Another study at Yale University showed that mice mounted a stronger immune response when they were injected first and then boosted with a nasal vaccine, as opposed to getting a nasal vaccine alone, as per a report in Time magazine.?

In the United States, the idea is that nasal and oral vaccines would be given mainly as boosters since most of the people would have had their first doses as injections by the time they are developed.

It may be noted here that these are animal studies and data from human trials, which are?underway in parts of the world, would give a better understanding.

Oral, nasal vaccines would be more accessible

Oral and nasal vaccines – at least some of them – would be more affordable and accessible than most of the vaccines being injected right now.

Since these vaccines would be dripped into your upturned nose and mouth like polio drops, the requirement of a nurse versed in giving injections can be done away with. Moreover, some of these vaccines can be stored at higher temperatures, allowing a longer shelf-life and administration in far-off areas.?

The USA Today reported?about a nasal vaccine being developed at America’s Icahn School of Medicine at Mount Sinai, “The vaccine also can be stored in a regular refrigerator rather than being kept frozen, which will make it cheaper and easier to provide to low- and middle-income countries.”?

Peter Palese, who is part of the team making the vaccine at Mount Sinai, told USA Today, “We can probably make this for 30-cents a dose versus $30?for an mRNA vaccine like Pfizer-BioNTech or Moderna's.”

Theoretically, such vaccines that replicate in the body may also last longer, noted Dr Spearman, cited above, in a USA Today story.

What are the risks of nasal vaccines?

Getting the dosage correct can be harder with nasal vaccines than a shot, especially with young children. If someone has a stuffy nose or sneezes out a part of the vaccine before it’s completely absorbed, this can result in a lower-than-desired dose.

There are some unique health risks too. All vaccines go through rigorous safety testing and clinical trials, but these processes are especially important for nasal vaccines due to the simple fact that the nose is close to the brain.?

In 2000, 27.7 per cent?of people who received an inactivated intranasal influenza vaccine in Switzerland developed transient facial paralysis – also known as Bell’s palsy.?

Later, researchers found that a bacterial toxin added to the vaccine to enhance the immune response was the culprit.

This is the only reported instance of neurological issues stemming from intranasal vaccines, but it is something to consider.

How long until intranasal Covid-19 vaccines are ready?

As of late May 2022, there are no approved Covid-19 intranasal vaccines for human use.?

There are currently seven in clinical trials, and three of them – manufactured by Beijing Wantai Biological Pharmacy, Bharat Biotech, and Codagenix and Serum Institute of India – are in phase-3 human trials.

In the coming months, the results of these trials will not only show how safe these promising new vaccines are, but also if they perform better than the vaccines in use today.

The Covid-19 pandemic will eventually transition to endemic stage. The pace, however, will be different in parts of the world.
Most of the world has done away with large lockdowns and countries are pressing ahead with targeted measures like vaccinations, boosters, and better treatments. The idea is that you would have to live with the virus.

It is believed that there would be a time when Covid-19 would be like any other disease out there. To get to such a stage, not only death and severe disease, but also infections and transmissions would need to be checked, which are the most distinguishable features of oral and nasal vaccines.

Therefore, the success of these vaccines could be critical to the world's transition out of the pandemic in future.

(with inputs from PTI, The Conversation)