Shape of vaginal suppositories affects willingness-to-try and preference

HIV and other sexually transmitted infections (STIs) are a global threat to public health that maybe countered, in part, by microbicides. A successful microbicide must be both biologicallyefficacious and highly acceptable to users. Sensory attributes have a direct influence on productacceptability. We created a series of vaginal suppositories appropriate for use as microbicides toinvestigate the influence of shape on women's willingness-to-try. The influence of perceived sizeand firmness on acceptability was also assessed.Sexually-active women (n=99) were invited to participate in an evaluation of vaginal suppositoriesin 5 different shapes including: Bullet, Long Oval, Round Oval, Teardrop and Tampon. Thevolume (3 ml) and formulation for these 5 prototypes were identical. After manipulatingprototypes ex vivo (in their hands), participants rated their willingness-to-try on a 100-point visualanalog scale. The appropriateness of size and firmness were evaluated using 5-point just-aboutright(JAR) scales. Each participant evaluated all 5 prototypes individually. Samples werepresented in a counterbalanced monadic sequence using a Williams design.Mean willingness-to-try varied by shape, with Bullet and Long Oval receiving significantly higherscores. This was consistent with JAR data for size, as 70 and 65% of women indicated theseshapes were `just-about–right', respectively. In contrast, a minority of women endorsed the other 3shapes as having a size that was `just-about-right'. The proportion of women who felt the firmnesswas `just-about-right' was uniformly high, irrespective of shape, suggesting prior attempts tooptimize the formula were successful. Perceptions of size and firmness were influenced by thephysical length and width of the prototypes, in spite of having constant volume. Women showedhigh willingness-to-try when asked to assume they were at risk. These results are relevant forbehavioral and formulation scientists working on microbicides, to better understand the influenceof sensory attributes on acceptability, as acceptability and compliance ultimately impacteffectiveness.