To examine human papillomavirus (HPV) series completion in older adolescents and assess vaccination completion opportunities missed by providers.

Electronic medical records were queried for women 18-24 years old who initiated the HPV vaccine in the Adolescent Medicine, Young Mother's, or Family Planning clinics at Children's Hospital Colorado from January 1, 2010-December 31, 2012. Clinic visits during appropriate dosing intervals of HPV vaccine at which the second (4-14 weeks after first dose) or third (21-40 weeks after first dose and >12 weeks after second dose) doses were not administered were counted as “missed opportunities.”

A total of 1072 female adolescents initiated the HPV series during the study period; 20.9% completed the series within 1 year. Of these, 33.7% who did not receive their second dose had at least 1 missed opportunity and 25.5% who received the second but not the third had a missed opportunity. Women who initiated the vaccine in the Family Planning clinic were less likely to have missed opportunities than those in other adolescent clinics (36.2% vs 56.4%; P < .001).

A significant number of female adolescents who initiated the HPV vaccine attended clinic visits at which opportunities for vaccine continuation and completion were missed. This emphasizes the importance of provider awareness of vaccine updates at every adolescent visit. Our overall completion rate is significantly lower than published rates and might reflect older adolescents' inexperience in managing their own preventive health care. Our results clearly identify the need for provider and patient interventions to improve vaccine series completion.