I suspect you didn’t mean this to come out as typed, but let me offer a few thoughts.
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A nasal spray is essentially how infections are “administered” as it is. It starts in the upper respiratory tract usually, in the nose/sinuses. Mind you the viral load is introduced over minutes and hours vs in a second, so it’s not exactly the same. But the vaccine is introduced the same way the disease is.
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Now if we’re are talking about administering vaccination, nasal spray has been scientifically proven to be effective for some vaccines.
It has the advantage of not requiring NEEDLES that have to be sanitary before and during use and then safely disposed(maybe disinfected and reused, but that’s risky).
Those same needles turn some people off of getting vaccinated where they would otherwise do it.
Injecting something into a human body is inherently risky, hence the sanitary concerns so something other than just the vaccine isn’t introduced.
IIRC, many spray vaccines are stabler than injectables and don’t have as strict storage requirements such as cold temps. But take longer to develop.
Mind you, if you have an injectable vaccine and no spray available, being picky may be a bad idea.