My vet decided this year not to give my dog the lepto vaccination. Last year he was very ill, and there's a small - teeeeeeeeeeeeny, tiny, really - chance that the vaccine may have triggered the problems. The vet thinks that we're safer without it than chancing a reaction. According to him, when they DO see vaccine reactions, it's normally due to the lepto vaccine and they're seeing a few more of that recently - it's not incredibly common, but it seems to be happening more and more with the new vaccines. We are even taking the precaution of dosing Tommy with Benadryl before/during/after his other vaccinations as well, also recommended by the vet just to be on the safe side.
What kind of dog is Oliver? The vet also said that some breeds are more at risk of a reaction to the lepto vaccine... pugs, yorkies, and a few others, I can't remember which ones.
If it were up to me, I would leave the lepto out for Oliver as well - I'm leaving it out due to a small possibility, but you KNOW that Oliver has a problem with it.