Measures

The primary outcome of interest was number of HPV vaccine doses received. Teens with zero recorded doses were classified as “unvaccinated,” those with 1–2 doses as “partially vaccinated,” and those with ≥3 doses as “fully vaccinated.” All parents were asked “Has a doctor or other healthcare professional ever recommended that [TEEN] receive HPV shots?;” those reporting a recommendation were asked at what age the provider recommended the teen should start vaccination. Data on provider-recommended age were only analyzed for girls, as routine HPV vaccination of boys at 11–12 y old was not recommended until late 2011.⁶

Parents of partially vaccinated teens were asked “Do you plan to have [TEEN] receive all 3 shots of the HPV series?;” those responding “yes” were asked why the teen had not yet received all 3 doses. Parents of unvaccinated teens were asked “How likely is it that [TEEN] will receive HPV shots in the next 12 months?;” responses were combined into “very/somewhat likely,” “not too likely/not likely at all,” and “unsure/don't know.” Respondents reporting intention to vaccinate in the next 12 months were asked about the most important factor that would determine when their teens were vaccinated, while those reporting no or unknown intention to vaccinate were asked the main reason why their teens would not be vaccinated in the next 12 months. Respondents with no or unknown intention to vaccinate were also asked at what age they planned to vaccinate their teens against HPV. (Respondents reporting “provider did not recommend” as their main reason for non-vaccination were not asked this question.)

Parents of teens who were not fully vaccinated were asked if they knew how many shots are included in the HPV vaccination series; those reporting yes were asked to provide this number. Parents were classified into “aware” and “not aware” of HPV vaccination recommendations based on responses to these 2 questions. All parents were asked to rate their agreement with 7 statements about HPV vaccine on a scale of 0 (strongly disagree) to 10 (strongly agree). These statements covered vaccine safety, efficacy against several health outcomes, and importance of vaccination for boys vs. girls.