Vaccines have been one of the biggest success stories of modern medicine in preventing diseases and saving millions of lives worldwide. Conventionally vaccines are administered through intramuscular or subcutaneous injections. However, a new route of vaccine administration is emerging which could revolutionize disease prevention – nasal vaccines.

How do nasal vaccines work?

Nasal vaccines work by utilizing the immune system present in the nasal mucosa. When administered via the nose, these vaccines activate both mucosal and systemic immunity against pathogens. The nasal mucosa contains specialized cells and immune structures that induce immune responses tailored for respiratory infections.

Upon nasal delivery, the vaccine is able to stimulate production of immunoglobulin A (IgA) antibodies in the nasal mucosa as well as IgG antibodies in the bloodstream. IgA antibodies act as the frontline defence by blocking entry and spread of pathogens in the nasal passage and respiratory tract. At the same time, circulating IgG antibodies provide long-lasting protection.

This dual mucosal and systemic immunity conferred by nasal vaccines mimics the natural immune response triggered during respiratory infections. It generates immune memory at the primary site of viral/bacterial entry as well as systemically. This makes nasal vaccines highly effective at preventing respiratory illnesses.

Advantages of nasal vaccines

Some of the key advantages of nasal vaccines over traditional injectable vaccines include:

 

Needle-free administration: Nasal vaccines don't require use of needles or syringes for delivery. This eliminates pain and risk of needle-stick injuries which can boost vaccine acceptance and coverage.

Induce mucosal immunity: By stimulating immune cells in the nasal mucosa, these vaccines induce protective immunity precisely where respiratory pathogens first enter our body. This offers superior protection against diseases affecting the respiratory tract.

Avoid cold chain requirements: Most nasal vaccines are thermostable and can be administered without strict cold chain storage. This makes them better suited for mass immunization programs in tropical countries and rural areas with limited cold chain infrastructure.

Self-administration: Nasal vaccines can potentially be self-administered, which reduces burden on healthcare workers. This allows for scaling up vaccine programs more efficiently.

Low-cost production: Production of subunit nasal vaccines is relatively simple and cost-effective compared to injectable or live-attenuated vaccines. This makes them affordable for developing countries.

Recent advances in nasal vaccines

Encouraged by these advantages, global efforts are underway to develop more nasal vaccines against major infectious diseases:

- Influenza

The most clinically advanced nasal vaccine is the influenza vaccine. Several NASVAC (nasal spray flu vaccine) products are approved for use including FluMist Quadrivalent by AstraZeneca. Clinical trials show similar or superior efficacy compared to injectable flu shots in both children and adults.

- COVID-19

Nasal COVID vaccines aim to block viral entry and transmission by stimulating IgA in the nasal mucosa. Candidates from Beijing Wantai Biological Pharmacy, BIOVIR and BiondVax show promise in animal and early stage human trials. Larger efficacy studies are currently underway.

- Respiratory syncytial virus (RSV)

An experimental nasal RSV vaccine called rRVG by Nexbio aims to prevent lower respiratory tract infections in older adults. Phase 1 data showed it induced protective IgA and IgG levels in nasal and serum samples respectively.

- Pneumococcus

An intra-nasal recombinant pneumococcal vaccine developed by Bharat Biotech has completed Phase 1 and 2 trials in India. It aims to provide broader serotype coverage than the existing injectable pneumococcal vaccines.

Future prospects

With further research and development investments, nasal vaccines hold significant potential to transform global immunization practices in the coming decades. Some experts project nasal delivery will become the dominant immunization route for various key diseases like influenza. But larger effectiveness trials are still needed before widespread introduction. Overall, nasal vaccines represent a promising approach to make immunization even more convenient and protect populations from major infectious threats in the respiratory tract.

 

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