I received rabies vaccine in thighs. paperwork says it should be given in deltoids. what benefit would there be to doing it this way?

Could vs should: The drug makers propose a standard method of vaccine delivery to meet the requirements to get it approved for use. It is not a requirement. Most vaccines are given into muscle, rather than into fat or other tissues where the blood flow (absorption) is not as consistent. Thighs are fine and are the go to place where we give vaccines to infants who lack enough deltoid mass to be reasonable.