Associations between prior HPV4 vaccine doses and cervical cancer screening participation.

BACKGROUND:Cervical cancer screening, regardless of HPV vaccination, is a cornerstone of cancer prevention. This study evaluated associations between prior HPV vaccine doses and initiation and continued participation of screening by age at vaccination. METHODS:Using electronic medical records for a safety net healthcare system (Truman Medical Center), women aged 14-26y vaccinated (n=1123) between 07/01/2006 and 10/1/2009 were randomly selected and matched on birth year and health campus to unvaccinated (n=1123) women. Frequency of screening was determined through 07/01/2013. Hazard ratios (HR) for screening were estimated using Cox proportional hazards regression. RESULTS:Screening rates were higher after vaccination: unvaccinated (53%), first (62%), second (59%) or third (61%) doses. Women who initiated screening were less likely to complete the vaccine series, regardless of age. Women receiving one dose were more likely than unvaccinated women to initiate screening (HR=2.98 95% Confidence Interval (CI):2.45-3.61) and were more likely to screen than those receiving two (1 vs. 2, HR=2.94 95% CI:2.09-4.14) or three doses (1 vs. 3, HR=3.15 95% CI:2.21-4.48). Compared to unvaccinated women, women <21y who completed 3-doses were 1.8-times more likely to screen at ≥21y, whereas vaccinated women ≥21y were more likely to screen regardless of number of doses (p<0.0001). CONCLUSIONS:Women who were vaccinated were more likely to screen than unvaccinated women; screening rate was highest after and occurred closest to the first vaccine dose. Research evaluating the efficacy of a one-dose vaccine is warranted and may provide both higher vaccination and screening rates.