What are the opportunities and challenges facing the nasal spray vaccine in the "front line" of the new crown virus invasion?

When it comes to vaccinations against the new crown, we may all think of injections

Recently, an article published on the C&EN website under the American Chemical Society discussed the pros and cons of intranasal vaccines, as well as its development history and challenges that need to be resolved

The uniqueness of nasal spray vaccine: stimulate mucosal immune response

When most pathogens enter the human body, the first "line of defense" that needs to be crossed is the mucosal tissue on the surface of the respiratory tract and digestive tract

Although the currently developed injectable new crown vaccine can effectively stimulate the body's antibody and cellular immune response, they cannot effectively stimulate the mucosal immune response

The advantage of the nasal spray vaccine is that in addition to stimulating the systemic antibody and cellular immune response, it can also stimulate the mucosal immune response, thereby providing more comprehensive immune protection

▲The mucosal immune response has multiple mechanisms against pathogens (picture source: reference [3])

The development history and challenges of nasal spray vaccine

In the history of vaccine development, many vaccines that stimulate mucosal immune responses have been approved for marketing

The development of nasal spray vaccines is relatively slow.

However, compared with injection vaccines, the development of nasal spray vaccines needs to face unique challenges

However, it is not so easy to detect the level of IgA antibodies secreted by the mucosal immune response

In addition, it is not a simple matter to deliver the correct dose of nasal vaccine to the nose.

These factors make it more difficult to accurately measure the immune response to the nasal spray vaccine.

Many nasal spray vaccines have entered clinical trials

According to statistics from the World Health Organization, among the more than 100 new crown vaccine candidates currently in clinical trials, at least 7 vaccine candidates are delivered in the form of nasal spray

In preclinical studies, the nasal spray new crown vaccine has shown the potential to effectively stimulate mucosal immune responses and systemic immune responses

With multiple injectable new crown vaccines that have been urgently authorized to be widely used around the world, the nasal spray vaccine that is still in the development stage may not immediately have a major impact on the control of the new crown epidemic

For developers of nasal spray vaccines, the outbreak of the new crown epidemic has given them a good opportunity to verify the feasibility of nasal spray vaccines through clinical trials

"Obviously, injectable vaccines are effective in most cases

Reference materials:

[1] Intranasal vaccines aim to stop COVID-19 where it starts.
Retrieved June 11, 2021, from https://cen.
acs.
org/pharmaceuticals/vaccines/Intranasal-nose-vaccines-stop-COVID/99/i21? utm_source=mostread&utm_medium=mostread&utm_campaign=CEN

[2] Altimmune Demonstrates Strong Neutralization Of South African Variant In Preclinical Study Of Intranasal AdCOVID™.
Retrieved June 11, 2021, from https://ir.
altimmune.
com/news-releases/news-release-details/altimmune-demonstrates- strong-neutralization-south-african

[3] Mucosal Immunity in COVID-19: A Neglected but Critical Aspect of SARS-CoV-2 Infection.
Retrieved June 11, 2021, from https:// Neutra and Kozlowski, (2006).
Mucosal vaccines: the promise and the challenge.
Nature Review Immunology, https://doi.
org/10.
1038/nri1777