I don't know how much into the episode you watched, but she got a tetenus shot because she was going on a trip to Italy (I guess Italy was swarming with cases of tetenus back then

) and she developed a terrible rash on her rear end (heehee.) The rash then started spreading to the rest of her body.
She went to the doctor and he gave her some pills to take for the rash, and he didn't explain to her the risks or how to take the pills, so she took all of them and had a terrible reaction to the pills and had to cancel her trip to Italy.