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# Offering HPV vaccine at 9-10 raised series completion by age 13 from 45% to 62%
- URL: https://www.coios.me/offering-hpv-vaccine-at-9-10-raised-series-completion-by/
- Published: 2026-09-29T12:50:15.000Z
- Updated: 2026-09-29T21:01:15.000Z
- Description: In a cluster-randomised trial across 31 US paediatric practices, introducing HPV vaccination at ages 9-10 rather than 11-12 brought median series completion forward from 13.3 to 12.2 years and raised completion by age 13 from 45.1% to 61.6%.
- Author: Daniel Ryan
- Tags: Behavioural science, Changing behaviour at scale, Cancer, Infection and pandemics, United States, #preprint, #new, #item, #source-2026-09

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.*

Source

[medRxiv, 27 September 2026](https://doi.org/10.64898/2026.09.24.26363898?ref=coios.me)

DOI

10.64898/2026.09.24.26363898

Type

Preprint

Design

Two-arm cluster-randomised trial, 31 paediatric practices in Colorado and California, Oct 2021-Apr 2026

Verdict

New finding

Driver

[Changing behaviour at scale](https://www.coios.me/d-behaviour-change/)

Driver

[Cancer](https://www.coios.me/d-cancer/)

Driver

[Infection and pandemics](https://www.coios.me/d-infectious-disease/)