When Willow reads the doctor's papers, she says that he was trying to inoculate the kids. But inoculation is the introduction of a small amount of virus in the body to build immunity in the hopes that larger exposure will have no effect. It is pointless to attempt to inoculate someone who already has the virus, it only makes them sicker. So either the doctor was applying it wrongly (not farfetched considering his reputation), or he was using some other method and referring to it by the wrong name.
EditS 7 : Ep 22
Aired 5/20/03
S 7 : Ep 21
Aired 5/13/03
S 7 : Ep 20
Aired 5/6/03
S 7 : Ep 19
Aired 4/29/03
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