This preprint reports a two-arm cluster-randomised trial in 31 paediatric practices in Colorado and California, comparing introduction of HPV vaccination at ages 9-10 with the routine 11-12 years between October 2021 and April 2026. Median age at series completion was 12.2 versus 13.3 years (adjusted HR 2.37, 95% CI 1.94 to 2.89), and completion by age 13 was 61.6% versus 45.1% (RR 1.37). Tdap receipt was higher in the intervention arm, and receipt of both other adolescent vaccines by age 13 did not differ.
Why it is interesting: Randomised evidence that the age at which HPV vaccination is introduced changes series completion by age 13.