yes! some nasal/inhaled vaccines are in trials in other countries, but i am not aware of such progress in the US. it will really help PREVENT infections and not just reduce the severity of symptoms.

It's not a vaccine, but there are existing nasal sprays [0] with iota-carrageenan, which has anti-viral properties and has been shown in-vitro [1] to be effective against covid:

[0] https://www.betadine.ca/nasal-spray/

[1] https://journals.plos.org/plosone/article?id=10.1371/journal...

Can you cite any sources on differences in tissue response from route of administration?