<p><strong>PURPOSE: </strong>The aim of the study was to determine whether supplementing a bundled recommendation (recommendation for all 11- to 12-year-old platform vaccines) with tailored messaging that addressed one versus all parental concerns improved human papillomavirus (HPV) vaccination intent among mothers.</p>

<p><strong>METHODS: </strong>We conducted a Web-based randomized controlled trial, randomizing mothers who did not intend to vaccinate their 11- to 14-year-old child against HPV to (1) bundled recommendation video ("control"); (2) control&nbsp;+ video addressing the top HPV vaccine concern; or (3) control&nbsp;+ ≥1 videos addressing all concerns. Outcomes were HPV vaccination intent (1&nbsp;= extremely unlikely and 10&nbsp;= extremely likely) and strength of main concern (1&nbsp;= a little concerned and 10&nbsp;= very concerned). We assessed differences in intervention effects using generalized linear models for vaccine intent and mixed models for the strength of main concern.</p>

<p><strong>RESULTS: </strong>Of the 762 mothers, 51% had a female child, 82% of children were white, and 90% were non-Hispanic. The mean intent to vaccinate postintervention ranged from 3.5 (95% confidence interval [CI]&nbsp;= 3.1-3.8) in the control group to 4.2 (95% CI&nbsp;= 3.9-4.6) in the all-concerns group (p&nbsp;= .01). The mean strength of the concerns declined pre- to postintervention by .1 (95% CI&nbsp;=&nbsp;-.1 to .3) in the control group (p&nbsp;= .42), .6 (95% CI&nbsp;= .4-.9) in the top concern group (p &lt; .001), and .7 (95% CI&nbsp;= .5-1.0) in the all-concerns group (p &lt; .001). However, the mean strength of the main concerns postintervention remained high (≥7.0 for each group).</p>

<p><strong>CONCLUSIONS: </strong>Tailored messages addressing all concerns improved HPV vaccination intent and reduced the strength of the main concern more than bundled messages alone, but intent remained low and strength of the main concerns remained high in this vaccine-hesitant population.</p>