Background: The quadrivalent HPV vaccine series is approved as 3 separate doses at: 0, 2 ±1 months, and 6 ±2 months. Current HPV vaccination rates are increasing, but few studies have described the prevalence and characteristics of delayed dosing.
Objectives: To determine the proportion and characteristics of girls and women in North Carolina who received HPV vaccine outside the recommended dosing schedule.
Methods: The data source, the North Carolina Immunization Registry, is used by NC health departments and over 600 private providers. We selected females nine through 26 years of age who received at least one dose of HPV vaccine between 6/8/2006 and 2/17/2009. Interval periods were measured with respect to the first HPV vaccine dose and compared to the recommended schedule. Multivariate logistic regression was used to evaluate the association between delayed vaccination and race, VFC funding, provider type, age, ethnicity, and county.
Results: Of 138,827 females who received ≥ 1 dose, 22.9% were not documented to have received another dose, 22% received only two doses, and 55% received three doses. The overall proportion of women with a delay between the first two doses was 39.4% and between the first and third doses was 43.2%. The median intervals from a primary dose for a delayed 2nd and 3rd dose were 5.7 months and 10.8 months, respectively. Only 28.1% of females received all three doses at the recommended intervals. White race (OR: 1.68, [1.61, 1.75] vs. non-White) and private funding (OR: 1.38, [1.32, 1.43] vs. VFC funding) were associated with on time dosing.
Conclusions: Most females receiving the HPV vaccine have a delay in subsequent doses, which warrants investigation of the effect of delayed dosing intervals on the immunogenicity of the vaccine. Because dosing delay is frequent, strategies to enhance on-time receipt of HPV vaccine should be broadly encouraged.