I personally recommend you keep the appointment. Remember that while vaccinating rabbits is very new to the US this past year, it has been a practice for hundreds and hundreds of domestic rabbits owned by responsible owners in European countries and Australia for years. While they have different vaccines themselves (we don’t import from them I believe), it is a very normal practice to vaccinate rabbits in general– it just happens to be novel to us in the US!
For information about the Medgene vaccine, see here: https://rabbit.org/faq-for-medgenes-rhdv2-vaccine/
I volunteer for two rescues operating in the DC/MD/NoVA area and none of our vaccinated rescue rabbits have had side effects. My personal rabbits were both vaccinated at this past weekend in VA, and they had no side effects. The only reported side effect instance reported at that veterinary practice was swelling at the injection site for 48hrs.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.