I wonder if that is a historical or legal artifact. Medicine wasn't always so refined to the point that the vaccines were pure pathogen in chemical carrier and

I wonder if that is a historical or legal artifact. Medicine wasn't always so refined to the point that the vaccines were pure pathogen in chemical carrier and didn't have some human specimen material trace or otherwise when isolating. Both for transport safety concerns and exemptions (no arresting the doctor for carrying vaccines even if he technically is guilty of transporting importing dissected human remains not fuffiling legal burial requirements when it takes a microscope to detect the human cells) would make sense.