Key takeaways:

• Clinics in Colorado and California were randomized to begin recommending HPV vaccination at ages 9 and 10 or 11 and 12.
• Recommendations for starting the series at ages 9 and 10 significantly increased completion by age 13.

WASHINGTON — Children were twice as likely to begin and complete the HPV vaccine series at clinics that began recommending it at ages 9 and 10 instead of ages 11 and 12, according to findings presented at IDWeek.

The HPV vaccine provides protection against 6 types of cancer. The CDC recommends HPV vaccination starting at age 11 or 12 years, but says it can be given as young as age 9 years. The American Academy of Pediatrics and American Cancer Society recommend the vaccine for children aged 9 to 12 years.

Data derived from O’Leary ST, et al. Impact of switching human papillomavirus (HPV) vaccine initiation to ages 9-10 on vaccination coverage: results of a cluster randomized controlled trial. Presented at: IDWeek; Oct. 21-24, 2026; Washington.

Most practices in the United States recommend vaccination beginning at age 11 years, according to Sean T. O’Leary, MD, MPH, pediatric infectious disease specialist at University of Colorado Anschutz.

Despite strong evidence supporting the vaccine, uptake is lagging. As of 2023, the National Cancer Institute reported that 57.3% of adolescents aged 13 to 15 years were up to date on their HPV vaccination, far below the goal of 80% that HHS set in its Healthy People 2030 initiative.

“Prior to our trial, several observational studies suggested that starting at ages 9 or 10 years help children finish the series on time more often, but those studies couldn’t tell us whether earlier vaccination caused the improvement or whether these clinicians or families who vaccinated earlier are simply different,” O’Leary said during a press conference prior to IDWeek.

O’Leary and colleagues set out to answer this question with a cluster randomized controlled trial at 31 pediatric clinics in Colorado and California. According to O’Leary, 16 practices were randomly assigned to recommend HPV vaccination at ages 9 and 10 while 15 practices continued recommending it at ages 11 and 12. All clinicians received training about increasing HPV vaccination, and those in the investigational group received additional training about discussing earlier vaccination with parents, according to O’Leary.

Overall, more than 62,000 children and adolescents visited the practices during the 5-year study period from 2021 to 2026, O’Leary said, and 28% of 9- to 13-year-old patients were up to date with their HPV vaccination.

O’Leary reported that children who visited practices in the 9 and 10 group completed the HPV vaccine series 1 year earlier than children in the 11 and 12 group (median age at completion, 12.2 years vs. 13.3 years). By age 13, 61% of children in the 9 and 10 group had completed the series, compared with 45% in the 11 and 12 group. Additionally, 77% of 13-year-olds had initiated the series in the 9 and 10 group, compared with 67% of the adolescents in the 11 and 12 group.

After adjusting for confounding factors, the researchers reported that children and adolescents were more than twice as likely to initiate (adjusted HR = 2.52; 95% CI, 1.93-3.27) and complete (aHR 2.85; 95% CI, 2.12-3.83) the HPV vaccine series at practices that started recommending it at ages 9 and 10.

“Introducing HPV vaccine at 9 or 10, rather than 11 to 12, led to statistically significant and clinically meaningful gains in both starting and finishing the series without detecting any negative effects on visits or other vaccines,” O’Leary said. “What our data show is that the age at which families first hear the recommendation changes how many children are protected and how soon.”

O’Leary and colleagues previously published qualitative research about physicians’ experience with earlier HPV vaccine administration. The physicians reported that parental pushback and acceptance did not change, and that conversations tended to be shorter in the 9 and 10 groups than the 11 and 12 groups. The main concern that parents expressed was expecting a vaccine-free visit and feeling surprised that one was recommended at the 9- and 10-year-old visits.

O’Leary shared a couple of reasons why he believed vaccine uptake rose with earlier recommendations. At 11 and 12, children are due for multiple vaccines, including Tdap and meningococcal vaccines, so HPV is more likely to be skipped at those visits.

“Early vaccination also may more effectively frame HPV vaccine as cancer prevention not necessarily a conversation about sexuality, which had also been a concern,” he said. “For clinicians who now start at 11 or older, we would suggest at least considering earlier introduction in their offices.”