“ I guess my question is why were not the 2nd class of vaccines (nasal) pursued first?”
I don’t know. The FluMist nasal vaccine is limited to younger folks, so that potential market limitations may have scared developers - but also, the priority targets for vaccination are the elderly.
Ah, I didn't know that. Seems like a darn good reason. What's the problem with the FluMist vaccine for us "old" farts?