Coronavirus vaccine: How do nasal vaccines work? Are they better than the injected ones?

With the rampant rise in infection rates, developments are happening speedily as researchers toil to develop the world's first vaccine to prevent further spread of COVID-19.

From the production, licensing and the way it is made, a lot of things are being streamlined, since this is the first time a vaccine of such a kind is being worked on. While vaccines are usually injected orally or through the arm, some groups are also using another approach- developing nasal vaccines to target the virus faster.

Prominent groups across India and the world are currently doing so. Is it better than the regular vaccine? Does it have a better shot at providing immunity? Here is an explainer:

Nasal injection of vaccines is a novel approach some scientists are trying right now wherein instead of a shot injected in the arm, the vaccine is delivered right to the respiratory system.

Because the target is to deliver a dose which goes right into the respiratory pathways, the vaccine is either injected through a specific nasal spray, or through aerosol delivery.

As far as we know, COVID-19 is a respiratory infection, which can often first start off from the respiratory passage and lead to further inflammation and side-effects. What it also does is block the airways and lead to symptoms like breathlessness.

The novel approach behind developing a nasal vaccine is that by injecting a vaccine in such a fashion, the mucous would be able to identify the trigger (SARS-COV2), develop immunity and stop it from proceeding further and targeting the body. Thus, by blocking entry at the initial point of contact, this approach may be able to better tackle and prevent the spread of the deadly infection.

For the same, scientists have identified two types of cells in the nasal cavities which act as the first infection points for a virus to enter the body. The mucal membranes and linings present along with the respiratory tract act as the first line of defence and prevent harmful germs and bacteria from causing further damage. A vaccine jab, which is powerful here, would help prevent the virus from causing extensive harm.

Such an approach will also help the vaccine to do a multi-pronged attack on the virus the moment it tries to breach the body's barriers, said an expert, Deepta Bhattacharya, an immunologist at the University of Arizona in an interview.

Experts also believe that nasal vaccines would be able to reach the lungs, wherein the cells which are majorly attacked by the virus would be present.

The primary aim of any vaccine is to provide immunity against a certain infection and prevent damage. While coronavirus vaccines work by decoding the gene sequence of the SARS-COV-2 virus and spike up antibodies in the body, an intranasal vaccine is an advanced manner to ensure that the body can be doubly protected against viral loads. The nasal vaccine targets immune cells present in the mucosal membrane and tissue- which provides systematic as well as mucosal immunity present in other sites such as lungs and the intestines.

Hence, a nasal vaccine may be more capable of inoculating crowds against the deadly infection and prevent even mild symptoms from developing. Extensive study is being done regarding the same.

There's also another benefit to nasal vaccines. Since they focus on the immune cells lined along with the nose and the respiratory tract, the T and B cells present there (which are body's immunity cells) spike up production of antibodies, which are quite helpful in improving gut sensitivity, promote healing as well as clearing out pathogens from the airways. Once vaccinated, the T cells can memorize and stop further attacks from happening.

Intranasal vaccines are still in their nascent stage of development. However, at least five medical groups, including one from India are working on developing a Coronavirus targeting nasal vaccine which is in different phases of study right now.

Coroflu, a vaccine jointly developed and worked on by vaccine maker FluGen and the University of Wisconsin-Madison is India's third prime vaccine candidate after COVAXIN and ZyCOV-D which uses a self-limiting version of existing influenza virus to stimulate immunity and spike up production of helpful antibodies in the system. The vaccine is expected to delve into human trials by the end of 2020.

Nasal sprays and vaccines are still in the experimental phase and there's a lot more research that's needed before we get conclusive evidence. However, experts have let out a word of caution, saying that a nasal vaccine could be deliberately exposing a large area to a new entity, which could trigger the problems in some cases.