— Kids who started the series at age 9 or 10 years were more than twice as likely to get both shots
October 21, 2026 • 3 min read
WASHINGTON -- Children who started the two-dose human papillomavirus (HPV) vaccine series at age 9 or 10 years were more than twice as likely to get both shots versus those who began later, a cluster randomized trial showed.
Across 31 U.S. pediatric practices, kids who were recommended to receive HPV vaccination starting at age 9 or 10 had better initiation and completion rates by age 13 versus those who received vaccination starting at age 11 or 12:
- Initiation rates: 77.1% vs 67% (adjusted HR 2.52, 95% CI 1.93-3.27)
- Completion rates: 61.6% vs 45.1% (aHR 2.85, 95% CI 2.12-3.83)
"What our data show is that the age at which families first hear about the HPV vaccine recommendation changes how many children are protected, and how soon," said Sean O'Leary, MD, MPH, of the Children's Hospital Colorado Anschutz Medical Campus in Aurora, during a press briefing ahead of the IDWeekopens in a new tab or window annual meeting. "For clinicians who now start at 11 or older, we would suggest at least considering earlier introduction in their offices."
Though safe and highly effective at preventing HPV infection and a range of subsequent HPV-related cancersopens in a new tab or window, vaccine uptake may not be high enoughopens in a new tab or window to deliver herd immunity. Key vaccination guidelines suggest that an earlier start to HPV vaccination is possible, and previous research has shown that a head start can be effectiveopens in a new tab or window.
The CDC recommends HPV vaccinationopens in a new tab or window for children at ages 11 or 12 years, though the agency notes that vaccination can start at age 9. The American Academy of Pediatrics recommends starting the vaccine series between 9 and 12 yearsopens in a new tab or window, "at an age that the provider deems optimal for acceptance and completion of the vaccination series."
O'Leary noted that his study's results should help shift recommendations toward stronger endorsements of an earlier starting age. "We would suggest that policymakers consider a preferential recommendation for starting at ages 9 or 10, rather than simply permitting it," he said.
The trial randomized 31 pediatric practices in California and Colorado from 2021 to 2026 to either introduce the HPV vaccine at ages 9 or 10 (16 practices) or to continue recommending a start at ages 11 or 12 (15 practices). All practices received online training on recommending HPV vaccination, as well as annual booster training and practice-level data reviews. The early-start clinics also received guidance on talking with parents about starting HPV vaccination earlier.
"That's important, because we tested the timing of the change by itself -- not a package of interventions," O'Leary noted.
The trial included 62,271 children and adolescents ages 9 to 13 years. Nearly half (48.5%) were female, and roughly 22% were on Medicaid.
Median age at vaccination initiation was 11.0 years in the early-start clinics compared with 11.8 years in the standard-start clinics, while median age at vaccination completion was 12.2 years and 13.3 years, respectively.
Getting an earlier start at age 9 didn't affect receipt of other vaccines or later well-child visits, "which was one of the concerns going into this study," O'Leary noted. Rates of well-child visits at 11 or 12 years didn't differ between the two groups, nor did meningococcal or tetanus, diphtheria, and pertussis (Tdap) vaccination rates by age 13.
Parental hesitancy and acceptance also didn't differ much between the groups. The main pushback in the early-start group came from parents who didn't realize a shot would happen at the well visit and had told their children there wouldn't be shots, O'Leary said.
There are practical reasons why getting a head start on HPV vaccination may work better, he explained. The 9-year-old wellness visit is less crowded from a vaccine standpoint than the multiple-vaccine visit at age 11 or 12. Earlier HPV vaccination also may allow clinicians to more effectively frame the vaccine as cancer prevention, he added, rather than as a conversation about sexual health.
Research also shows that vaccination at younger ages still leads to longer-term protection. "What we've seen is there doesn't appear to be any waning of protection," O'Leary said. "It's really a remarkable vaccine in that sense."