Estimating the direct effect of human papillomavirus vaccination on the lifetime risk of screen-detected cervical precancer.

ABSTRACT

Birth cohorts vaccinated against human papillomavirus (HPV) are now entering cervical cancer screening. Assessment of (pre)cancer (CIN3+) risk is needed to assess the residual screening need in vaccinated women. We estimated the lifetime (screen-detected) CIN3+ risk under five-yearly primary HPV screening between age 30 and 60, using HPV genotyping and histology data of 21,287 women participating in a screening trial with two HPV-based screening rounds, 5 years apart. The maximum follow-up after an HPV-positive test was 9 years. We re-estimated the CIN3+ risk after projecting direct vaccine efficacy for the bivalent and the nonavalent HPV vaccines, assuming life-long protection. The lifetime CIN3+ risk was 4.1% (95% confidence interval 3.5-4.9) and declined by 53.5% and 70.5% after bivalent vaccination without and with cross-protection, respectively, translating into a residual lifetime CIN3+ risk of 1.9% (1.4-2.4) and 1.2% (0.9-1.5). The CIN3+ risk declined by 88.5% after nonavalent vaccination, translating into a residual lifetime CIN3+ risk of 0.5% (0.2-0.7). The latter risk increased to 1.6% when vaccine protection only lasted until the first screening round at age 30. Among HPV-positive women with abnormal adjunct cytology, the nine-year CIN3+ risk was 16.9% (8.7-32.4) after nonavalent vaccination. In conclusion, HPV vaccination will lead to a strong decline in the lifetime CIN3+ risk and the remaining absolute CIN3+ risk will be very low. Primary HPV testing combined with adjunct cytology at five-year intervals still seems feasible even after nonavalent vaccination, although unlikely to be cost-effective. Our results support a de-intensification of screening programs in settings with high vaccination coverage.