Coronavirus vaccines: Will nasal vaccines prove effective against COVID-19? Here's everything you need to know

On Monday, Prime Minister Narendra Modi addressed the Indian masses and spoke about the various plans that the government has laid out to combat the deadly virus. In his address, he also said that research on developing nasal vaccines as an alternative to intramuscular vaccines are underway. This, according to him, could boost India's anti-COVID vaccination drive, which is why it is important to be aware of the key points about what an intranasal vaccine is, how it works and what are the disadvantages you must be aware of.

As opposed to injected vaccines, that are injected into the skin with the help of injections (needles), usually nasal vaccines are sprayed into the nostrils. It can be done with the help of a syringe with no needle, a nasal spray, liquid medicine or special aerosol delivery.

While the virus commonly enters your body through your nose, the vaccine then intercepts the virus and causes your immune system to make proteins in your blood and in your nose to combat the virus. This also prevents the virus from multiplicating.

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Since most viruses, including the ones associated with SARs-COV-2, enter the body through the mucosa and infect the cells and molecules present in the mucosal membranes, nasal vaccines are seen as an effective solution for the same.

On the contrary, intramuscular vaccines or injected vaccines fail to trigger such an immune response from the mucosa and depend on immune cells from other parts of the body. It produces circulating Immunoglobulin G (IgG) antibodies that fight off deadly pathogens even before they can cause severe tissue damage, but are not exactly effective in managing viral entry into the body.

Apart from that, nasal vaccines are easier to administer and may provide easy immunity. An effective nasal jab can not only protect against COVID-19, but also directly interact with T-cells that exist in the nose and the throat and target the immune cells present in the mucosal membrane.

Given that intranasal vaccine produces secretory Immunoglobulin A (IgA), it manages to evoke 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. This somehow not only combats the virus but also avoids transmission. While nasal vaccines generate a robust and effective mucosal immune response, it avoids further damage of the lungs, in terms of COVID-19.

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Although the intranasal vaccines curb and neutralise viral infection in the mucosal membrane itself, which is the point of entry for the virus, the antibodies that it produces may not be as strong in the lower respiratory tract as against the upper respiratory tract.

Additionally, experts believe that intranasal vaccines may fail to provide effective and long lasting immunity to the patients against the virus.

Another disadvantage of the vaccine may be associated with its safety. While it uses live attenuated virus, there is a slight chance of reversion of neuro-attenuation, meaning that the virus can attain back its ability to cause disease in the individual.

However, when it comes to developing nasal vaccines for COVID-19, researchers are still working towards reaching a possible solution.

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Currently, trials to produce intranasal COVID vaccines in India are in progress. BBV154, an intranasal vaccine developed by Hyderabad-based Bharat Biotech, is already in the pre-clinical trial phase. If the nasal vaccines turn out to be a success, it will only make India's COVID vaccination drives more flexible. Also, this “could be a game changer for children,” as per the World Health Organisation (WHO).