We offer several recommendations about development and reporting of measures, in hopes of motivating efforts toward the development and use of standardized measures with demonstrated validity and reliability. We begin with recommendations that are applicable to measurement of any study topic, then address some of the unique challenges of measuring acceptability and uptake of a new vaccine for a sexually transmitted disease.
As this field of research advances, it is critical that increased attention be focused on the development of measures so as to improve our understanding of factors that influence vaccine uptake. One step toward this goal would be greater use and explication of conceptual underpinnings of studies. Theory provides conceptual clarity for construct definitions, guides the designation of primary and secondary outcomes, can identify potential mediating and moderating factors, determine the timing of data collection, and dictate analytic strategies. Greater use of standardized construct definitions, for example as provided by the NCI website, would facilitate consistent measurement and enable greater comparability of findings across studies. The majority of theory-based studies included in this review applied the Health Belief Model and Theory of Reasoned Action, which focus heavily on the influence of individual perceptions and behavior. We advocate use of a conceptual framework that also considers the influence of interpersonal relationships, institutional and health-system factors, mass media, as well as vaccine policy [101
]. For this, an ecological model, such as that described by McElroy and colleagues [102
], can facilitate a more comprehensive understanding of vaccine attitudes and behaviors in a broader context [101
]. Moreover, it may be useful to draw from theories of informed decision making, such as those developed by O'Connor [103
], as well as decision sciences [104
As noted, the majority of studies to date focused on HPV knowledge. As knowledge levels increase over time and with greater exposure to information about the vaccine [3
], additional emphasis on attitudes and beliefs is warranted, particularly because knowledge is a weak predictor of behavior [105
]. While it is likely that intervention efforts will likely focus on disseminating knowledge, we recommend additional study of the specific domains of knowledge required for informed decision-making, such as vaccine risks, benefits, limitations, as well as predicted efficacy and duration of effect.
Exploration of other constructs, such as intention and actual behavior, will also be increasingly important as awareness of HPV and the vaccine increases. As time passes, it will be critical to measure compliance with the three-dose series and with cervical cancer screening recommendations, particularly among groups that suffer a disproportionate burden of HPV-associated illness. In addition, studies are needed to better understand provider knowledge and behaviors. Much attention has focused on individual or parental characteristics that influence decisions to vaccinate. However, if a provider does not recommend vaccination, individual and parental decisions may be inconsequential. It will also be important to understand the impact of direct-to-consumer advertising, extensive media attention, and controversial legislative efforts to mandate vaccine coverage on HPV-related attitudes and behaviors. While study of HPV vaccine uptake presents unique challenges given this context, studies of uptake of the Hepatitis B vaccine [106
] and acceptability of future HIV vaccines [108
] share similarities (e.g., sexual transmission) and could provide insights for the development of standardized measurements.
When necessary to develop original measures, review of items by a panel of experts [110
], cognitive interviewing [111
], and pilot testing of items among the intended audience [110
] is recommended to optimize content validity, minimize “floor” or “ceiling” effects, and to improve understandability. Such efforts to develop questions to assess theoretically-derived constructs associated with HPV vaccine uptake are currently underway [112
]. In addition, because HPV is a sexually-transmitted virus and some parents are concerned that vaccination may result in unsafe sexual behaviors, sensitivity is also needed in the development of items to assess vaccine decisions. To reduce the potential for social desirability bias or underreporting, questions should be constructed with neutral wording, could incorporate question stems that indicate researcher impartiality (e.g., “Many people believe that there are advantages and disadvantages to HPV vaccination”), or might utilize open-ended response options (e.g., “What are your concerns about vaccinating your daughter?”) [110
Overall, inclusion of more detail about measures in study reports such as information about methods used to develop measures, changes made to existing measures if used, as well as strategies employed to assess validity and reliability would facilitate methodologic advancements. Reporting standards, CONSORT (Consolidated Standards of Reporting Trials) [96
], TREND (Transparent Reporting of Evaluations with Non-Randomized Designs) [98
], and STROBE [99
] provide detailed guidance for reporting important details about study methods and results for the respective types of study they address. Greater consideration and use of these guidelines would ensure the availability of information needed to assess strengths and limitations of research in this field. Moreover, establishing a central repository for measures would aid investigators in identifying tested items, the use of which would facilitate cross-comparison of study findings. Agencies funding such research ought to collaborate to create this repository and consider requiring this sharing function for newly funded research.
We also recommend more attention to the development and testing of measures for high-priority audiences. While women in the HPV vaccine “catch-up” age group (i.e., 13–26 years of age) are currently an important target audience, parents will likely be the primary audience at whom future vaccination efforts are directed, particularly those who are members of `minority' racial and ethnic groups, individuals with low literacy skills, and non-English speakers. These groups experience disparities to access of health information and may also have diminished access to vaccine [113
]. Notably, rates of initial vaccination appear to be higher among those with lower levels of income and education, as well as Hispanics [114
]. This may be due to reduced financial barriers to the vaccine because of the federal Vaccine for Children Program, which makes vaccine available free-of-cost. Nevertheless, we believe that these groups remain a high priority for intervention efforts because of diminished access to information about the vaccine [113
], lower rates of completion of the three-dose series [115
], and unremitting disparities in cervical cancer incidence and mortality [116
]. Development of valid and reliable instruments to assess knowledge, attitudes and behaviors across audiences that are diverse with respect to race/ethnicity, language, literacy levels-- as well as gender [117
] now that the vaccine is available to boys-- will require time, resources, and a concerted effort among investigators. In the meantime, giving research consumers sufficient information with which to assess the quality of measures is essential for judicious application of study findings.
Evidence-based interventions for HPV vaccination are needed. Such interventions will be guided by the literature on factors associated with vaccine intentions and acceptability. While the currently-available literature provides the preliminary foundation from which to launch such efforts, additional development of measures to assess factors that influence vaccine decision-making is needed to further advance this goal.