Tdap-HPV vaccination bundling in the USA: Trends, predictors, and implications for vaccine series completion.

The Centers for Disease Control and Prevention (CDC) promotes taking a 'bundling approach' (i.e., administering Tetanus, diphtheria toxoids, and acellular pertussis [Tdap] and human papillomavirus [HPV] vaccines in the same way and on the same day) for adolescent vaccinations. Recent trends and patterns in Tdap-HPV vaccination bundling in the USA remain undocumented. In addition, the implications of bundling Tdap-HPV vaccination for HPV vaccine series completion remain unknown. To address these critical knowledge gaps, we performed a retrospective study using a nationwide sample of privately insured adolescents (Optum's de-identified Clinformatics® Data Mart Database). Tdap-HPV vaccination bundling (per 100 Tdap vaccination encounters) during 2014-2018 was estimated overall, for 50 states, and by adolescents' age, sex, and provider specialties. Survival model estimated the likelihood of series completion among 9-14-year-old adolescents. From 2014 to 2018, 560,806 adolescents received a Tdap vaccine of which 172,604 (30.8%) received the HPV vaccines on the same day. Tdap-HPV vaccination bundling (per 100 Tdap vaccinations) increased nationally, from 22.9 in 2014 to 39.1 in 2018 (P < 0.001); bundling was lowest in New York and New Jersey. The likelihood of receiving the Tdap and HPV vaccines bundled was higher for young and female adolescents. Adolescents who received their first HPV vaccine bundled with the Tdap vaccine were more likely to complete the series compared to those who received it alone (Hazards Ratio = 1.45; 1.43-1.48). HPV vaccination bundling has increased in recent years in the USA. The increased likelihood of HPV vaccine series completion provides important evidence supporting the adoption of same-day Tdap-HPV vaccine administration in clinical practice to boost HPV vaccination coverage.