AWWWWWWWW poor little Scout.
I sure do hope he feels better soon. My baby, Hootie, always feels so crappy after her shots, but she has never felt like this before! She is still a puppy, though, and is still receiving her puppy shots. Your post got me nervous since Hootie always feels crappy, so I searched the internet for info on the Lepto vaccine. I found that the strains of Lepto going around these days are not even the strains that are vaccinated for. Also, there are more and more dogs that are having allergic reactions to the vaccine. I bet that is what is wrong with Scout...poor little baby.
I am going to have to talk to my vet about this before Hootie gets her yearly vaccine for Lepto.