I don't know but I'll take a bee sting over Cancer, HIV, or Hep C anyday of the week:-)
There website just states it is tolerable without anesthetic; and because it does not induce unwanted immune responses, it can be repeatedly administered for booster vaccinations.
I can tell you that it electroporation use to be done under a local, (Novocaine) and if I were getting it done I would request it. The comparison I have gotten is think of one of those shots you have gotten that was more painful than it should of been. I have also been told it was better than a cortisone shot someone got in a joint.