Effect of age at initiation of the human papillomavirus vaccine on the association between race/ethnicity and completion of the vaccine series

Background: Up-to-date (UTD) of the human papillomavirus (HPV) vaccine series has been low despite 2016 recommendations for 2 doses among initiators <15 years of age and 3 doses for 15+ year olds. This study examined how age at initiation affected the association between race/ethnicity and UTD among adolescent HPV vaccine initiators. We also examined how administration of other adolescent vaccines affected UTD. Methods: A secondary analysis of The National Immunization Survey – Teen data between 2016 and 2020 was conducted. Characteristics associated with initiation of the vaccine series was examined and used to evaluate UTD among initiators. All data were weighted. Associations between characteristics and HPV vaccine initiation were examined using Rao Scott chi-square tests and univariable logistic regression. Multivariable binary logistic regression models stratified by race/ethnicity calculated the strength of association between independent variables and odds of initiation and UTD among initiators. Results: The final sample size was 99,719 with 67,855 (68.1 %) initiating HPV vaccination. Among HPV vaccine initiators, Hispanic and black adolescents had lower odds of UTD. However, 9–10-year-old initiators had increased odds (aOR: 5.71; 95 %CI: 3.78–8.63) of UTD compared to 12-year-old initiators. Increased odds of UTD among initiators younger than 12 years were found across racial/ethnic groups. Flu vaccination was associated with decreased odds of UTD among white (aOR: 0.76; 95 %CI:0.65–0.88) and black adolescents (aOR: 0.67; 95 %CI: 0.46–0.96). Conclusion: Strong recommendations to ensure patients are UTD on the HPV vaccine series are essential to improving UTD among all adolescents and follow-up should occur when administering other vaccines to reduce missed opportunities.