Starting HPV vaccination at nine or ten sharply improves on-time completion

A cluster randomised trial found that children offered the HPV vaccine at nine or ten were more likely to start and complete the series by age 13 than those approached at 11 or 12.

Starting the human papillomavirus vaccine series at ages nine or ten appears to give children a better chance of finishing it on time, according to a study presented at IDWeek 2026 in Washington. In a cluster randomised trial involving 31 paediatric practices in Colorado and California, children whose doctors began the conversation at ages nine to ten were more likely to start and complete the series by age 13 than those whose practices waited until ages 11 to 12.

Sean T. O’Leary, a paediatrician at the University of Colorado Anschutz Medical Campus and Children’s Hospital Colorado, told conference attendees that an earlier start also seemed to make the conversation easier and shorter. He said clinicians who still wait until a child is 11 or older should consider moving the discussion forward, while policymakers should consider whether a preference for beginning at nine or ten would improve uptake.

The findings add to a debate that has already seen some disagreement between professional groups over when to begin the vaccine. The US Centres for Disease Control and Prevention says the series can start at 11 or 12, although it may be given from age nine, while the American Academy of Pediatrics recommends starting between ages nine and 12, at the time a clinician judges most likely to lead to acceptance and completion. Earlier studies have suggested that earlier initiation improves uptake, and a recent narrative review in the Journal of Adolescent Health found that starting at nine or ten is linked with better completion.

In the trial, practices assigned to the earlier-start approach received training that included suggested language for parents about beginning the vaccine series at nine or ten, while the comparison group received more general vaccination training. Over the course of the study, 77.2% of children in the earlier-start group began the series by age 13, compared with 67% in the later-start group. Completion rates were 61.7% versus 45.1%, respectively. The median age of completion also came sooner in the earlier-start group, at 11.8 years, than in the later-start group, at 13.3 years.

Researchers also interviewed clinicians and office staff in the earlier-start group and found that parents often accepted the vaccine, with fewer discussions about sexual activity than when the shot was raised later. The main friction, staff said, came from families who had expected a shot-free visit. O’Leary said the team did not see signs that starting HPV vaccination earlier reduced well-child visits or affected uptake of other recommended adolescent vaccines, such as Tdap and MenACWY. He noted, however, that the clinics were all urban or suburban, so the results may not translate cleanly to rural practices or to states beyond California and Colorado.

Simon Parzen-Johnson, a paediatrician at the University of Chicago and Comer Children’s Hospital, told Medscape Medical News that the findings were encouraging and fit with the view that many age-based norms are partly conventional. O’Leary, meanwhile, acknowledged the wider US debate over vaccines and said it should not change what individual paediatricians do in the examination room, where the focus remains on a child’s best interests. The study was funded by the National Cancer Institute, and O’Leary reported no disclosures.