Early Initiation of HPV Vaccination and Series Completion in Early and Mid-Adolescence.

OBJECTIVES: Routine human papillomavirus (HPV) vaccination has been recommended in the United States since 2006 but rates remain suboptimal. State-based studies suggest that initiation in late childhood at ages 9 to 10 years compared with the recommended early adolescent ages of 11 to 12 years improves series completion. No study with national scope has explored the early initiation-HPV series completion relationship. This study addresses this knowledge gap and explores whether early initiation might improve series completion by increasing time to target completion age (time pathway) or by moving initiation to an earlier developmental stage (development pathway). METHODS: Using data from the National Immunization Survey-Teen 2017-2020, a retrospective cohort of 19 575 15 to 17 year olds who initiated HPV vaccination between ages 9 and 12 years was assembled. Time pathway endpoints were series completion by ages 13 and 15 years. The development pathway endpoint was completion within 3 years of initiation. RESULTS: Early initiators were more likely to complete by ages 13 (74.0% vs 31.1%, P < .001) and 15 (91.7% vs 82.7%, P < .001) years but less likely to complete within 3 years (82.3% vs 84.9%, P = .007). The association of early initiation to completion was maintained in multivariable analyses for time pathway endpoints (age 13 years adjusted odds ratios [AOR] = 6.16; 95% confidence interval [CI], 5.45-6.96, age 15 years = AOR 2.56; 95% CI, 2.14-3.14) but not the development pathway endpoint (AOR = 0.93; 95% CI, 0.80-1.07). CONCLUSIONS: Moving routine HPV vaccination to ages 9 to 10 may improve vaccination coverage rates in early and mid-adolescence. Providers should be vigilant to patient interactions after HPV series initiation to optimize public health benefits of vaccination.