TUESDAY, Oct. 27, 2026 (HealthDay News) -- Introducing the human papillomavirus (HPV) vaccine at ages 9 to 10 years rather than 11 to 12 years leads to a meaningful difference in initiation and completion of the vaccine series, including initiation and completion by age 13 years, according to a study presented at the annual meeting of the Infectious Diseases Society of America (IDWeek), held from Oct. 21 to 24 in Washington, D.C.Sean O'Leary, M.D., M.P.H., from the University of Colorado Denver Anschutz Medical Campus and Children's Hospital Colorado in Aurora, and colleagues examined the impact of switching HPV vaccine initiation from 11 to 12 years to 9 to 10 years in a cluster randomized trial among 31 pediatric practices in Colorado and California from 2021 to 2026. Sixteen practices were randomly assigned to introduce the vaccine at ages 9 to 10 years and 15 practices at ages 11 to 12 years.The researchers found that the median age at initiation and completion of the series was 11.0 and 12.2 years and 11.8 and 13.3 years in the 9- to 10-year-old arm and 11- to 12-year-old arm, respectively. By age 13 years, 77.1 and 61.6 percent of adolescents had initiated and completed the series, respectively, in the 9- to 10-year-old arm compared with 67.0 and 45.1 percent, respectively, in the 11- to 12-year-old arm (adjusted hazard ratios for initiation and completion, 2.52 and 2.85, respectively, for 9 to 10 years versus 11 to 12 years)."Lowering the age of vaccination holds promise for increasing the number of people protected against HPV, particularly as related cancers are on the rise," O'Leary said in a statement.Press ReleaseMore Information.Sign up for our weekly HealthDay newsletter