Hazard Ratios of Vaccine Receipt During the 12-Month Study Period, Comparing Study Arms

Intervention ArmHPV #1a (n = 17 658)HPV #2a (n = 5142)HPV #3a (n = 4788)
Hazard Ratiob (95% CI)PHazard Ratiob (95% CI)PHazard Ratiob (95% CI)P
Combined versus none1.6 (1.2–2.1).0011.3 (1.1–1.5).0081.5 (1.3–1.7)<.001
Clinician only versus none1.5 (1.2–2.0).0031.0 (0.8–1.1).71.1 (0.9–1.3).2
Family only versus none1.1 (1.0–1.2).031.2 (1.1–1.3)<.0011.4 (1.2–1.5)<.001
Combined versus clinician only1.1 (0.9–1.2).21.3 (1.2–1.5)<.0011.3 (1.2–1.5)<.001
Combined versus family only1.4 (1.2–1.8).0011.1 (0.9–1.3).51.1 (0.9–1.2).2
Family only versus clinician only0.7 (0.6–0.9).0071.2 (1.0–1.4).021.2 (1.0–1.4).03
  • a For each dose, the population includes only adolescents who had not received the dose at the study start and were eligible for that dose. For example, an adolescent could not be eligible for HPV dose 2 unless she had received dose 1.

  • b Hazard ratios were calculated by using Cox regression, adjusting for covariates and accounting for clustering. A hazard ratio of 1.6 means that the instantaneous rate of receiving the vaccine is 60% higher in the intervention group relative to the control group. Results in Table 4 translate these hazard ratios into standardized differences in time to vaccination and rates to enhance clinical interpretability.