Increases in HIV/AIDS transmission and prevention knowledge were largest in Asian nations. Improvement in transmission knowledge was greater to the extent that the nation had a lower HDI and a larger proportion of the sample reported exposure to the campaign. Increases in prevention knowledge were larger following longer campaigns. Interventions that reportedly included demonstrations of condom use did not significantly improve prevention knowledge compared with interventions that did not report condom demonstrations. No other coded report characteristics (eg, publication status), campaign characteristics (eg, number of communication channels, message branding, reported theoretical background, condom distribution) or sample characteristics (eg, age, gender, proportion sexually active, pre-campaign rate of condom use) were significant predictors of effect size magnitude for any outcome of interest.
Results from the current meta-analysis of 54 reports evaluating 72 interventions demonstrated that mass media-delivered interventions increase condom use and improve transmission and prevention knowledge. To the best that we know, our meta-analysis is the first to examine published and unpublished mass media reports across the world. Average effect sizes in this study were of small to medium magnitude (0.25–0.39; Table 1); yet, results were marked by heterogeneity, and several study characteristics moderated intervention efficacy.
First, as previous meta-analytic work related to HIV prevention has demonstrated, this meta-analysis supports the conclusion that interventions achieve better results where the need is greatest,87–89 as demonstrated by the linkage between HDI and outcome measures (Table 2). Investing resources into areas of the world with lower social and economic development seems to yield greater returns than investing resources into those with greater development. In contrast, the CI results in Table 2 and in Figure 3 that include the value of 0 suggest that mass media interventions failed, on average, in relatively developed nations. The differential impact between nations scoring higher and lower on the HDI may be because of reduced “media clutter” in less developed nations, and differences in incidence rates and perceived risk.
Because most interventions included in this meta-analysis used multiple communication channels, it was impossible to tease apart the effects of different channels used in the interventions. Interventions often use as many communication channels as they can afford, consistent with studies that show reach and impact increasing as numbers of media and interpersonal channels increase.1,4,5 We found no evidence that number of channels was related to greater impact in the present meta-analysis. Unfortunately, studies tend to show the combined impact of all channels and messages; the way in which the media are used within an intervention may differ, and it would inform future interventions to know which types of media approaches work under what conditions.
Previous reviews of mass media–delivered interventions to prevent HIV/AIDS have addressed the variability in research design, methodology, and reporting of intervention development, content, and delivery.14–16 The most persistent hurdle in determining the efficacy of mass media campaigns is the lack of available comparison groups in the evaluation of these interventions; only 8 of the 72 interventions included in the present meta-analysis provided valid comparison group data. Because of the inability to reliably control access to mass media, it may be both difficult and costly to use true or quasi-experimental designs. As a result, many campaign evaluations compare pre- and post-campaign data or compare individuals who were or were not exposed to the campaign. Both of these evaluation methods have limitations. The former does not allow for direct attribution of changes in knowledge or behavior to the campaign message alone, although it is notable that in the current investigation, campaigns were more successful to the extent that more respondents reported exposure. Additional factors unrelated to a specific campaign, such as the social or political climate, public policy changes, current events, and the presence of multiple campaigns in a targeted area can influence HIV/AIDS-related knowledge and sexual risk behaviors, making it impossible to isolate intervention effects. Evaluations based solely on exposure are also limited in that exposure to mass media may be related to individual characteristics such as income, gender, relationship status, and age.90,91
As with other reviews, the results of the present meta-analysis are limited by the available studies and reflect the empirical state of the field. The intervention literature in general would benefit tremendously from the public availability of more quantitative evaluations (ie, using pre-campaign comparison groups or quasi-experimental designs), described in greater detail (eg, specifying media channels used). In cases where reporting space is limited, researchers can provide additional information regarding campaign details as online supplements to publications, provide references to more descriptive papers, or invite readers who desire additional information to contact them directly. It would also be beneficial to the literature to have studies include cost information to facilitate cost-effectiveness analyses. Additional information would allow for more nuanced theorizing about what sorts of mass media interventions may work best in different contexts.
Another limitation of the present study is that our database generally focused on short-term effects of the interventions, when media effects are most likely to be at their peak. In media research, effects tend to dissipate over time,92,93 and analysis of the rate of decay of HIV media interventions is best addressed in a meta-analysis designed to examine such effects. Still, intensive interpersonal HIV prevention strategies have been shown to have larger effects at extended periods (1–3 years) compared with briefer interpersonal interventions.94 Finally, the present article does not explore other aspects of campaign content and message design, and although campaigns from more than 30 countries were included, we limited our search to reports available in English.
Past meta-analyses of HIV prevention literature have focused almost exclusively on trials evaluating relatively intensive strategies that demand interpersonal interaction, often in small-group sessions that continue over a series of weeks or months.94–98 The current studies, in contrast, use media that often are brief, and only sometimes include interpersonal communication in clinics or with outreach workers. Despite the differences in channels between the current and previous meta-analyses, the effects on behavior change are similar in magnitude—small to medium, depending on moderating factors. Despite their modest size in absolute terms, for statewide or national media interventions the scope of their impact is quite large in absolute terms. Media campaigns are a means of “going to scale”—taking an intervention to large numbers of people.22
In summary, the present results provide strong testimony to the power that mass media campaigns can have for people living in nations most at need for HIV prevention and other health promotion interventions. Results also suggest that such campaigns generally lack effectiveness in relatively developed countries, where the need for health promotion is generally lessened except in particular locales.
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