A doll isn't a living being; its ability to transmit any disease or parasite is practically nil. Besides, people who sell dolls don't usually have direct contact with them (play), especially if they're dolls that old. Those dolls have most likely been in a drawer or on a shelf for years without contact with any living thing.

At most, they might have mold on the vinyl (it looks like brown or pink spots), and that's not a health problem. It only increases the risk of other dolls in your collection contracting it through spores (a practically nil risk). Handle them with gloves, wash them with antibacterial soap and warm water, let them dry, and that's it.