OBJECTIVE: To experimentally test whether presenting logically equivalent, but differently valenced effectiveness information (i.e. attribute framing) affects perceived effectiveness of the human papillomavirus (HPV) vaccine, vaccine-related intentions and policy opinions. METHODS: A survey-based experiment (N=334) was fielded in August and September 2007 as part of a larger ongoing web-enabled monthly survey, the Annenberg National health Communication Survey. Participants were randomly assigned to read a short passage about the HPV vaccine that framed vaccine effectiveness information in one of five ways. Afterward, they rated the vaccine and related opinion questions. Main statistical methods included ANOVA and t-tests. RESULTS: On average, respondents exposed to positive framing (70% effective) rated the HPV vaccine as more effective and were more supportive of vaccine mandate policy than those exposed to the negative frame (30% ineffective) or the control frame. Mixed valence frames showed some evidence for order effects; phrasing that ended by emphasizing vaccine ineffectiveness showed similar vaccine ratings to the negative frame. CONCLUSION: The experiment finds that logically equivalent information about vaccine effectiveness not only influences perceived effectiveness, but can in some cases influence support for policies mandating vaccine use. PRACTICE IMPLICATIONS: These framing effects should be considered when designing messages. Copyright (c) 2010 Elsevier Ireland Ltd. All rights reserved.
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