Talking about recommended age or fewer doses: what motivates HPV vaccination timeliness?

HPV vaccination is recommended for U.S. adolescents at ages 11-12 and requires two versus three doses if the series is started before age 15. We evaluated how talking about recommended age or fewer doses motivates on-time HPV vaccination. Our national, online experiment randomized 1,263 parents of adolescents to view one of three messages about HPV vaccination recommendations or no message. Messages framed guidelines as recommending: vaccination at age 11-12; fewer doses for those who start vaccination at age 11-12; or, fewer doses for those who start vaccination before age 15. We then assessed parents' preferred age for HPV vaccination, categorizing preferences of ≤12 years as on-time. Parents who viewed "at age 11-12" versus no message more often preferred on-time HPV vaccination (63% vs. 43%, p  .05). Parents who viewed "fewer doses before age 15" less often preferred on-time HPV vaccination (39%, p < .05). Recommending HPV vaccination at age 11-12 encouraged on-time vaccination, while offering fewer doses had little impact. Providers should avoid framing HPV vaccination guidelines in reference to age 15 because doing so may discourage on-time vaccination by introducing confusion about the recommended age.