Hopefully, if your dog has ever experienced a vaccine reaction, you recognized what you were witnessing and didn't lose your head.  It’s often quite stressful, nonetheless. There is really no need for you or the patient to endure that again, as long as you remember to take a few precautions.  Preparing for a future visit is actually quite simple, straightforward, and inexpensive, but it is unbelievably common for pet owners to forget the details (or even, improbably, the entire incident) during the twelve intervening months.  
To be clear, the whole job of the immune system is to remember things, so—without preventative measures—you can be sure the event will recur. Future vaccine-related incidents will be much less likely if you schedule only one shot per visit and separate those visits by 2-3 weeks. You will want to consult your pet's doctor for specifics, but my own patients are advised to start taking Benadryl (a preventative for allergic reactions of various types) at least one day in advance of the appointment.  If and when you are going to administer an over-the-counter medicine to your pet, you will need to obtain permission, and the correct recommended dose, from your provider.  Benadryl must be administered once every 6-8 hours (NOT once a day); otherwise, you will miss out on its protective effects.  I recommend that this medication be continued on schedule for a total of 3-4 days. It's always a good idea to bring up any important medical history at the outset of a vet appointment, and previous vaccine reactions definitely qualify.  Of course you will disclose any medication you've been giving at home.  It never hurts to ask whether all of the scheduled vaccines and intervals are appropriate to your pet's specific lifestyle; sometimes this type of advice will change from one year to the next.  Some veterinarians will elect to give an injection of additional medication at the time of the visit.  
The immune system is very complex and can be quite cantankerous.  Once it has misbehaved in conjunction with a particular vaccination, we must assume that it will attempt to repeat that behavior every single time the two come face to face.  To avoid an encore performance, you must take the same precautions for each and every vaccine encounter without fail. Even so, a frustrated immune system does occasionally spill over its protective barrier and stampede.  For that reason, we can never be perfectly confident that the visit will go off without a hitch. I always advise the owners of reactors to schedule their appointment first thing in the morning and to remain with the patient for at least four hours afterwards.  That way, the doctor will still be available for a phone call or visit in case it becomes necessary to adjust your protocol for future visits.  
Once you've located the sweet spot between reacting and overreacting, you will want to write down the steps and duplicate them every year.  If you stick to the recipe and remain alert, you can keep your reactor pet safe from infections and from himself.
Dr M.S. Regan