A meta-analysis of 54 cases testing the effectiveness of inoculation theory at conferring
resistance and examining the mechanisms of the theory was conducted. The analyses
revealed inoculation messages to be superior to both supportive messages and notreatment
controls at conferring resistance. Additionally, the results revealed refutational
same and refutational different preemptions to be equally effective at reducing attitude
change. However, the data were not consistent with some predictions made in narrative
reviews of inoculation. No significant increase in resistance as a function of threat or
involvement was found. Further, instead of a curvilinear effect for delay on resistance, the
point estimates from our meta-analysis revealed equivalent resistance between
immediate and moderate delays between inoculation and attack, with a decay in
resistance after two weeks.