Will Falconer, DVM Moderator
Just that ignorant reply: "it takes place within hours, not days" is so telling. It's actually far more common to see a vaccine reaction a MONTH after it's given, and it's not usually fever (which, as your cat demonstrated, can come much earlier, even though that's more rare). Given that level of "shoot first, ask questions later," you can appreciate why I'm so keen to make sure you're discovering the realities that are plainly present if a vet only cares to look for them.
I suspect this wake-up call has been a life changer for you and your cats, Ivette. Bravo for your resolve to never let this happen again!