Dr. Hibberd's answer:

 

Here is my opinion in a nutshell: The best is the nasal spray, followed by low-dose intradermal shot, then the conventional full-dose vaccine into the muscle. Some vaccines are better suited to some than others, so consult your physician on this.

 

Flu vaccines are basically formulations designed to combat several flu strains that are "predicted" to be prevalent for the upcoming 12 months. They are essentially the results of the educated guesses of experts predicting the strains of flu expected to be the most problematic. So the flu vaccine given as an injection is a polyvalent vaccine that contains several inactivated strains of flu.

 

There are various ways to receive flu vaccine now that were not generally available until recent years. The conventional shot into muscle (IM) is given in a standardized in dose. A reduced dose for intradermal administration seems to generate a superior immune response than the conventional IM shot, and a nasal spray administration that is probably the most effective vaccine if you qualify to receive it.

 

The nasal flu vaccine is also inactivated but unlike the injectable vaccine, the nasal variety may cause clinical flu-like symptoms in some people and is generally reserved for children and young adults.