One is to prevent the whole herd from being infected(eradicated possibly), the other is a sick member to choose their way to treat themselves. Grievance is a part of life, it is sad to see members go, but I can't compare between that and the herd disappearing completely(no one left to grief).

EDIT: also I can't help but feel that this claim puts Chemotherapy on the same level of effectiveness as Vaccines. I think all options should be exhausted before we start claiming chemo to be as miraculous as vaccines are.