Hannibal made no mention of what vampires might or might not worry about. The point was not that she was the one who was worried. Nothing would matter if somehow a contamination from her clothes got into a sample. Anything could alter results. Anything.
He carefully set up his station while the women got changed. Set out the implements that he would need, and calibrated his microscope. Then he made extra sure that the space was sterile and clean. Nobody had touched anything, but that didn't stop his habits from being exercised.
When the pair returned, he would be standing and waiting.