Trogdon JG, et al. - Researchers herein describe the transition from bi- and quadrivalent HPV vaccines to 9vHPV in aggregate. They also searched for determinants of the receipt of 9vHPV among youth following the introduction of 9vHPV in North Carolina. They reported a relatively quick transition from other HPV vaccines to 9vHPV. At the same time, they reported disparities in the diffusion of 9vHPV across North Carolina. Data showed that youth receiving the HPV vaccine were more likely to receive 9vHPV if they lived in a ZIP Code Tabulation Area (ZCTA) with a larger age-eligible (ie, 9–17) population, a health professional shortage area, or a higher number of annual outpatient visits per capita.