Starting HPV vaccination at age 9 boosts series completion

Clinical takeaway: Consider recommending HPV vaccination beginning at ages 9-10 rather than waiting until ages 11-12. In this randomized trial, earlier initiation substantially increased both vaccine uptake and series completion by age 13.

HPV vaccination is highly effective at preventing multiple HPV-related cancers, yet vaccination coverage remains below desired levels. Although the vaccine is approved starting at age 9 and the American Academy of Pediatrics supports vaccination between ages 9 and 12, most practices still introduce it at ages 11-12.

A cluster randomized controlled trial involving 31 pediatric practices in Colorado and California evaluated whether introducing HPV vaccination at ages 9-10 improves long-term vaccination rates compared with the traditional approach of introducing it at ages 11-12. Practices were randomized to one of the two strategies, and clinicians in all sites received training on HPV vaccine communication and implementation.

The earlier-initiation strategy shifted vaccination to younger ages and resulted in higher coverage by age 13. The median age of vaccine initiation was 11.0 years in practices introducing vaccination at ages 9-10, versus 11.8 years in practices introducing it at ages 11-12. Median age of series completion was 12.2 versus 13.3 years, respectively.

By age 13, 77.1% of adolescents in the early-initiation group had received at least one HPV vaccine dose, compared with 67.0% in the standard-initiation group, an absolute increase of about 10 percentage points. Series completion rates were 61.6% versus 45.1%, representing an absolute increase of more than 16 percentage points. Researchers reported that adolescents in the early-initiation practices were more than twice as likely to begin and complete the vaccine series during the study period.

The investigators concluded that a relatively simple change in vaccine timing could meaningfully improve HPV vaccine coverage and completion, potentially increasing protection against HPV-related cancers. The findings were presented at IDWeek 2026 and have not yet been peer reviewed.

“Lowering the age of vaccination holds promise for increasing the number of people protected against HPV, particularly as related cancers are on the rise,” said study presenter Sean O’Leary, MD, MPH.

Source: O'Leary S, et al. (2026 Oct) IDWeek 2026. Impact of Switching Human Papillomavirus (HPV) Vaccine Initiation to Ages 9-10 on Vaccination Coverage: Results of a Cluster Randomized Controlled Trial