Difference? Nasal spray is a live virus and the injection is not a live virus. Chances of getting the flu from the nasal spary is higher than the injection. I always get the injection - I'm a nurse.
Best remedy for any type of cold or virus get plenty of rest and fluids if you have fever that does not respond to Tylenol you need to see a doctor. Not a bad idea to see a doctor if your symptoms are not better in 48 to 72 hours with almost anything. Only cure for cold and virus is time, rest and fluids, sorry no magic pill.
nj