Effect of HPV Vaccine Introduction at 9-10 years: A Randomized Clinical Trial

In the US, Human papillomavirus (HPV) related cancers cause significant morbidity and mortality, yet HPV vaccine is underutilized. Vaccination is recommended routinely at age 11-12 years but can be given at 9 years. There is controversy about whether earlier introduction would increase completion of the HPV series before by age 13 years or whether it might decrease rates of delivery of other routinely recommended vaccines at 11-12-years [quadrivalent meningococcal conjugate (MenACWY) vaccine, and tetanus-diptheria-acellular pertussis (Tdap) vaccine].

To determine whether introduction of the HPV vaccine at ages 9-10 versus 11-12 years, results in earlier median age of series completion (primary outcome) and higher rates of initiation and completion by age 13 years. We also examined the effect of earlier introduction of HPV on rates of Tdap and MenACWY initiation and completion by age 13 years.

Two-arm cluster-randomized trial involving 31 pediatric practices in Colorado and California between 10/2021-4/2026. Practices were randomized using covariate constrained randomization within each state to Intervention (introduction of HPV vaccination at ages 9-10) or Control (introduction at ages 11-12). Both study groups received similar annual training about best practices for HPV vaccination with recommended initiation age as the only difference.

Age at HPV series completion was substantially earlier in the Intervention group (median 12.2 v. 13.3 years; adjusted hazard ratio [aHR] 2.37; 95% CI 1.94-2.89). Key secondary outcomes were also improved in the intervention group: age at series initiation (median 11.0 v. 11.8 years; aHR 2.19; 95% CI 1.84-2.62), series completion by 13 years (61.6% v. 45.1%; RR 1.37; 95% CI 1.04-1.74), and vaccine initiation by age 13 years (77.1% v. 67.0%; RR 1.15; 95% CI 1.00-1.33). The intervention group was more likely to receive Tdap (aHR 1.47;95%CI 1.13, 1.92) during the trial; receipt of both vaccines by age 13 years did not differ.

Earlier introduction of HPV vaccination resulted in earlier age of series completion, and more adolescents initiating and completing the series by age 13 without decreasing rates of other routinely recommended vaccines. Our findings support a preferential recommendation at 9-10 years.

NCT04722822 ClinicalTrial.gov.