Research That Matters (January 17 - 20, 2008)

Purpose. HIV vaccines to prevent HIV infection are one of our greatest hopes for controlling the epidemic. Nevertheless, the likely partial efficacy of initial HIV vaccines, fear of side effects, and high cost may present challenges for acceptability, particularly among communities disproportionately affected by HIV/AIDS. HIV vaccine availability does not guarantee uptake. Formative research among vulnerable communities is vital to bridging the gap between vaccine efficacy and its effectiveness in controlling the epidemic. We examined the acceptability of future HIV vaccines among diverse groups at risk, and the vaccine characteristics associated with vaccine acceptability.

Method. We conducted a representative, probability sample survey (in English or Spanish) of 978 participants across 36 venues in 3 categories (public STD clinics [n=333], Needle Exchange Programs [n=315], and Latino Community/HIV Prevention Clinics [n=330]). Of the 978, 952 (97%) completed the questions on HIV vaccine acceptability. Face-to-face interviews were administered using a questionnaire programmed on laptop computers. We assessed hypothetical HIV vaccine acceptability using conjoint analysis, a multi-attribute stated preference method. Conjoint analysis incorporated a fractional factorial experimental design to construct eight hypothetical HIV vaccines, each with 7 dichotomous attributes: efficacy (99% vs. 50%), side effects (none vs. minor), cost ($10 vs. $250), duration of protection (10 years vs. 1 year), breadth of protection (cross-clade vs. single-clade), doses (1 vs. 4), and route of administration (oral vs. injection). Each participant was presented with a set of 8 laminated cards, each describing an HIV vaccine with different characteristics; they rated the likelihood of accepting each vaccine on a 7-point Likert-type scale (from definitely, highly likely…to definitely not). The ratings were transformed into a 0-100 scale. We estimated the impact of each attribute on vaccine acceptability by using ANOVA for repeated measures within individuals, then aggregating across individuals.

Results. Overall, 48% were Latino, 21% African-American, 19% white, with a mean age of 37.7 years; 24% completed the interview in Spanish, 40% were women, and 30% had less than high school degree education. One-third reported injection drug use. In the past year, one-fifth reported an STD diagnosis, 16% paid sex, and 17% were sexually active men who had sex with men. Acceptability of 8 hypothetical HIV vaccines ranged from 87.9 (SD=21.6) to 30.8 (SD=32.1) on a 0-100 scale; mean = 54.9 (SD 19.5). Efficacy had the greatest impact on acceptability (27.5, 95% CI = 25.5 - 29.5; p<.0001), followed by side effects (12.7, 95% CI =11.0 - 14.4; p<.0001), cost (9.9, 95% CI = 8.3 - 11.5; p<.0001) and duration of protection (7.3, 95% CI = 6.0 - 8.6; p<.0001).

Conclusions and Implications. The modest overall acceptability of HIV vaccines combined with marked variation depending on vaccine characteristics suggests obstacles to future HIV vaccine dissemination. With 40,000 annual HIV incident infections in the U.S., each year of delay in dissemination may result in thousands of new infections that might otherwise have been prevented. Understanding factors associated with HIV vaccine acceptability in diverse populations will be essential for designing interventions to ensure broad HIV vaccine uptake.