I haven't seen any news on how effective the Chinese and Indian nasal vaccines are. Last I heard they weren't very effective with the current approach, and the shots work more effective, but that may be due to US bias in the news I'm seeing.

What they are trying to achieve is to provoke an immune response when the virus hits the mucosal layer, before the virus gets into the bloodstream, which would decrease contagiousness and harm from repeat infections. The reason the virus is so damaging is because once it gets into the bloodstream it can basically infect everywhere in your body and how much damage it does is based on how quickly your body recognizes the virus before it spreads.

There is also evidence the virus gets into the brain through the olfactory bulb, so stopping it at that point will help a lot, and also one of the reasons I think it's a good idea to use an anti-viral nasal spray, even if it doesn't fully protect you from catching the virus.

So, they would be a good thing. Less damage from the virus, less chance to spread it. Probably won't be a silver bullet because no one wants to pay for air filtration, or continue to try and control the spread of disease in schools, hospitals and other public spaces, but it would help.

Dr. Eric Topal is a good person to follow on twitter if you want updates on how it's going. So far there have been promising trials, not a sure thing, but promising. From what he's seeing he guesses we might see them at the end of 2024, but no one really knows.

https://erictopol.substack.com/p/covid-nasal-vaccines-get-a-boost