2 0 1 5 , ▁the ▁Oregon ▁Chi rop ract ic ▁Association ▁invited ▁Andrew ▁W ake field , ▁chief ▁author ▁of ▁a ▁fra ud ul ent ▁research ▁paper , ▁to ▁test ify ▁against ▁Senate ▁Bill ▁ 4 4 2 , ▁" a ▁bill ▁that ▁would ▁eliminate ▁non med ical ▁exem ptions ▁from ▁Oregon ' s ▁school ▁imm un ization ▁law ". ▁The ▁California ▁Chi rop ract ic ▁Association ▁lo bb ied ▁against ▁a ▁ 2 0 1 5 ▁bill ▁ending ▁belief ▁exem ptions ▁for ▁v acc ines . ▁They ▁had ▁also ▁opposed ▁a ▁ 2 0 1 2 ▁bill ▁related ▁to ▁v acc ination ▁exem ptions . ▁ ▁Home op ath y ▁ ▁Several ▁surve ys ▁have ▁shown ▁that ▁some ▁pract ition ers ▁of ▁home op ath y , ▁particularly ▁home op ath s ▁without ▁any ▁medical ▁training , ▁advise ▁patients ▁against ▁v acc ination . ▁For ▁example , ▁a ▁survey ▁of ▁registered ▁home op ath s ▁in ▁Austria ▁found ▁that ▁only ▁ 2 8 % ▁considered ▁imm un ization ▁an ▁important ▁prevent ive ▁measure , ▁and ▁ 8 3 % ▁of ▁home op ath s ▁survey ed ▁in ▁Sydney , ▁Australia , ▁did ▁not ▁recommend ▁v acc ination . ▁Many ▁pract ition ers ▁of ▁nat urop ath y ▁also ▁opp ose ▁v acc ination . ▁ ▁Home op ath ic ▁" v acc ines " ▁( nos odes ) ▁are ▁in effect ive ▁because ▁they ▁do ▁not ▁contain ▁any ▁active ▁ing red ients ▁and ▁thus ▁do ▁not ▁stim ulate ▁the ▁imm une