I took my kitten to the vet this morning. He received his distemper shot and frontline flea treatment. Everything seemed fine for 2 hours, then he started to sleep. He is still sleeping even as I type. He looks really tired and refused to eat his food. He is usually a very active kitten and always hungry for food. Maybe I am just paranoid, but it was really really cold out today so I am worried he might have got sick. Or is this the usual side effect of vaccination? If so how long will it last?