What is mucosal immunity?

**Bababam** (0:04)
What is mucosal immunity? Thanks for asking.
It was announced last week that Covid booster vaccines would soon be available to millions of people across the UK, including all over 50s and other people with underlying health conditions. In the meantime, new ways to combat the virus are emerging, specifically that of a nasal spray vaccine designed to boost mucosal immunity. Regular listeners may recall our recent episode on this kind of vaccine. Well, the latest developments this month saw a team of French researchers present promising results from preliminary clinical trials on mice and hamsters. How is mucosal immunity different to what's generated by traditional vaccines then? Traditional vaccines provide what is known as systemic immunity. That means Covid-19 jabs, which are administered intramuscularly, generate immune cells throughout the body. They are also effective at protecting the lungs from severe cases. But mucosal immunity is more relevant to the exact site of infection, i.e. the nasal cavity where the virus first enters the body. After all, it is still possible to carry and spread the virus while being asymptomatic. And this happens to some people who have been vaccinated by injection.
Let's listen to physician Armando Hasmdungun explain the phenomenon of mucosal immunity in a video posted on his YouTube channel.

**Armando Hasmdungun** (1:32)
The mucosal epithelial cells are continuously exposed to pathogens.
These are the cells lining the gut tract, our lung tract, our nasal cavity, for example. The mucosal surfaces constitute the largest and most important interaction between the body and the outside environment.

**Bababam** (1:52)
It's like having a barrier between the outside world and the body. Immune cells are able to identify and destroy pathogens as soon as they arrive, so they won't ever get close to the lungs. And the evidence seems to suggest the most effective way of inducing mucosal immunity is through a nasal vaccine. That produces a local response, immediately reducing the viral load and transmission to other people.
It may be more effective at preventing contagious variants, such as Delta, from spreading and leading to further waves of mass infection. Are you saying we won't ever reach herd immunity with the existing vaccines? The best way to reach herd immunity is to prevent the virus's transmission. Dealing with the pandemic requires various different approaches. Increasing mucosal immunity through intranasal vaccine seems to be one, while another is to find an effective treatment for those who can't or won't get vaccinated. In the meantime, the best course of action to stop the virus spreading is to follow public health guidelines, even when vaccinated.
There you have it.
Now you know what mucosal immunity is. In under 3 minutes, we answer your questions. What would you like to know about? Use the comments section to send us your questions.