Collie types can carry a genetic mutation called mdt1 that can increase sensitivity to invermection and many other drugs, including over the counter, non-Rx remedies. For instance my sister's first English Shepherd could not take Glucosamine without dire diarrhea and tummy upset. Google, you'll find tons of stuff on it.
Reputable breeders of Collie types (border, rough, smooth, sheltie, English Shepherd etc) will screen breeding stock for this mutation and try not to pass it on. Research also shows that neutered and spayed dogs are at increased risk for vaccinatin reaction. Separating vaccinations by a week or so can help but is hard to do. My Vet for instance uses a combined vaccine and cannot separate the distemper from the parvo. So unless I go somewhere else and spend a LOT more money, presuming I can find a Vet who is willing or able to purchase individual vaccine I'm scuffered.
Make sure you do separate rabies from the others by at least a week or whatever your Vet recommends. You can separate that one.
I love his name as well. Too bad he took it literally.
I hope you get him over this successfully but I fear you will have to be on alert for reactions to many other things as well. Nothing insurmountable though, Sis's first E.S. who had some of the same problems made it to nearly 17. Good luck.
ETA: oops, sorry. Mdr1 Not t. And I should add, other, non-Collie breeds are affected too. Whippets for instance. http://www.mwcr.org/be_aware.htm