Objective: To use the 3 dose Human Papillomavirus (HPV) vaccine administration (given at 0, 1-2 and 6 months) to quantify opportunities to improve efficacy in the delivery of preventive health services. Methods: This was a retrospective, claims-based analysis using data provided by a single managed care plan. Female patients aged 9-26 who were continuously enrolled between 2009 through 2011 and received ≥ dose of the HPV vaccine during 2010 were analyzed. The proportion of initiators who did and did not completed the vaccine series, the timing and location of doses, and the number of outpatient visits during which the vaccine could have been given to non-completers were determined. Results: 1,830 patients were analyzed in the 2010 sample. 843 (46%) were continuously enrolled during the three-year observation period. 500 (59%) completed 3 doses. Among completers, the interval range between doses 1 and 2 was 27-619 days (median 96 days). The interval range between doses 2 and 3 was 32-621 days (median 127 days). 261 (52%) completers received dose 2, and 139 (28%) received does 3 over 1 month late. Among the 343 non-completers, 137 (40%), and 206 (60%) completed 1 and 2 doses, respectively. 63% of single-dose recipients and 17% of 2-dose recipients had at least 1 visit within the eligible time period for administration. Conclusion: Nearly half of HPV vaccine initiators do not complete the vaccine series. Of those who do, a large percentage complete it late. This example quantifies the potential for reminders, registries and outreach to improve on-time dosage and completion.