The Costa Rica HPV Vaccine Trial (CVT) has documented cross-protection of the bivalent HPV vaccine against HPV31/33/45 up to seven years after vaccination, even with one dose of the vaccine. However, the durability of such protection remains unknown. Here, we evaluate different schedules of the vaccine’s efficacy against HPV31/33/45 out to 11 years post-vaccination, expanding to other non-targeted HPV types.
We compared the rates of HPV infection in vaccinated women to the rates in a comparable cohort of unvaccinated women. We estimated the average vaccine efficacy (VEavg) against incident infections and tested for a change in VE over time.
Among 3-dose women, we observed statistically significant cross-protection against HPV31/33/45 (VEavg=64.4%, 95%CI: 57.7% to 70.0%). Additionally, we observed borderline, statistically significant cross-protection against HPV35 (VEavg=23.2%, 95%CI: 0.3% to 40.8%) and HPV58 (VEavg=21.2%, 95%CI: 4.2% to 35.3%). There was no decrease in VE over time (two-sided p-for-trend>0.05 for HPV31, 33, 35, 45, 58). As a benchmark, VEavg against HPV16/18 was 82.0% (95%CI: 77.3% to 85.7%). Among 1-dose women, we observed comparable efficacy against HPV31/33/45 (VEavg=54.4%, 95%CI: 21.0% to 73.7%). Acquisition of non-protected HPV types was similar between vaccinated and unvaccinated women, indicating that the difference in HPV infection rates was not attributable to differential genital HPV exposure.
Substantial cross-protection afforded by the bivalent vaccine against HPV31/33/45 and, to a lesser extent, HPV35 and HPV58, was sustained and remained stable after 11 years post-vaccination, reinforcing the notion that the vaccine is an effective option for protection against HPV-associated cancers.

Published by Oxford University Press 2020.