Impact of 9-Valent Human Papillomavirus Vaccine on HPV Vaccination Coverage of Youths, Ages 9-17, in North Carolina

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  • February 22, 2019
Creator
  • Trogdon, Justin
    • Affiliation: Gillings School of Global Public Health, Department of Health Policy and Management
  • Shafer, Paul
  • Lindsay, Brianna
    • Other Affiliation: Merck & Co., Inc.
  • Coyne-Beasley, Tamera
Abstract
  • Background and Research Objectives Human Papillomavirus (HPV) Vaccination •Most common sexually-transmitted infection in the United States •Causes genital warts, and is associated with cervical, vaginal, vulvar, anal, penile, and throat cancers •Routine vaccination at age 11 or 12 years has been recommended by the Advisory Committee on Immunization Practices (ACIP) since 2006 for females and since 2011 for males HPV Vaccination Rates •In 2015, completion of the three-dose series among adolescents ages 13 to 17 was: •42% for girls •28% for boys •HPV vaccination coverage also lags far behind childhood and other adolescent vaccines. HPV Vaccine Types •Quadrivalent HPV vaccine (4vHPV) and 9-valent HPV vaccine (9vHPV) are currently licensed and indicated for use among both females and males in the US to protect against several of the most common HPV types associated with cancer. •Bivalent HPV vaccine (2vHPV) is indicated for females only •9vHPV is the most recent HPV vaccine to enter the market •Food and Drug Administration approval in December 2014 •ACIP recommendation in February 2015 Objectives: •The primary objective was to evaluate the impact of introduction of 9vHPV vaccine on •HPV vaccination uptake (# doses) •Initiation (>1 dose) •Completion (>3 doses) •Compliance (>3 doses within 1 year) •The secondary objective was to describe timing of administration and characteristics of children who received 9vHPV compared to those who received another HPV vaccine (2vHPV or 4vHPV) beginning in July 2015. Methodology: PRIMARY OBJECTIVE Design: Area-level interrupted time series Outcomes: Area-level uptake (doses), initiation, completion, and compliance rates Key explanatory variable: Indicator for the introduction of 9vHPVin NC in July 2015 Analysis •De-trended monthly time series to remove time trend and seasonality •Regression on an indicator variable for ZCTA/months post release of 9vHPV SECONDARY OBJECTIVE Design: Individual-level retrospective cohort Outcome: Indicator variable for receiving 9vHPV (relative to other HPV vaccine type) Key explanatory variables: Youth and area-level demographic characteristics and other area-level market characteristics Analysis •Logistic regression •Separate regressions by sex Data North Carolina Immunization Registry (NCIR) •January 2008 through October 2016 •Youth between the ages of 9 and 17 years in 2016 •Complete vaccination history for this cohort of youth •Excluded youth in the NCIR with missing values for date of the HPV vaccine, HPV vaccine type, sex or ZIP code •Primary objective: aggregated data to ZIP Code Tabulation Areas (ZCTAs) •Secondary objective: restricted sample to doses of HPV vaccine administered during or after July 2015 (introduction of 9vHPV in NC) Discussion Primary objective •Introduction of 9vHPV was not associated with changes in HPV vaccination rates in NC as measured by doses per capita or initiation, completion or compliance rates •Results did not change when we also included ZCTA-level characteristics and allowed for autoregression in the error terms. Secondary objective •Following the introduction of 9vHPV, youth receiving the HPV vaccine were more likely to receive 9vHPV than other HPV vaccine types if they lived in a ZCTA with •a larger age-eligible (i.e., 9 to 17) population, •a health professional shortage area, or •a higher number of annual outpatient visits per capita. •Following the introduction of 9vHPV, youth receiving the HPV vaccine were less likely to receive 9vHPV than other HPV vaccine types if •they were older, •received a publicly-funded dose, or •lived in a ZCTA with a higher percentage of the population with less than a high-school education or •a higher number of religious organizations. Limitations •NCIR does not include complete coverage of privately funded vaccines, vaccines given by pharmacies or to youths who may have moved out of state •Not representative of U.S. or areas of country with different demographics and regional patterns of care •Bias could remain from changes in unobserved confounders concurrent with the introduction of 9vHPV (e.g., changes in outreach policies in the state) Summary •Introduction of 9vHPV was not associated with changes in HPV vaccination rates in NC •Transition from 4vHPVto 9vHPV was quick •Disparities in the diffusion of 9vHPV across areas of NC
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  • Academy Health. Annual Research Meeting (2017: New Orleans, LA)
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