Assessing the epidemiological impact on cervical cancer of switching from 4-valent to 9-valent HPV vaccine within a gender-neutral vaccination programme in Switzerland

Background An infection with high-risk human papillomavirus (HPV) is the obligatory aetiological factor for the development of cervical cancer. In Switzerland, the prevention strategy for cervical cancer is based on primary prevention via HPV vaccination and secondary prevention with an opportunistic screening programme for precancerous lesions. Vaccination is recommended to 11–26 years old male and female persons. The objective of the study was to assess the epidemiological impact on cervical cancer of switching from the currently implemented programme with the 4-valent vaccine to the 9-valent vaccine, in an 11–26 years old gender-neutral vaccination programme in Switzerland. Methods A previously validated dynamic transmission model of HPV infections was adapted and calibrated to the Swiss setting assuming an 80% coverage rate in HPV-vaccination and lifelong vaccine type-specific protection. A gender-neutral vaccination programme (males and females) for 11–26 years old with a 9-valent HPV vaccine was compared with the current 11–26 years old gender-neutral 4-valent vaccination programme. Sensitivity analyses were conducted in order to test the impact of lower vaccination coverage rates and a shorter duration of protection on the model outcomes. Results In Switzerland, a 9-valent gender-neutral vaccination programme would result in an additional prevention of 2979 cervical cancer cases, 13,862 CIN3 and 15,000 CIN2 cases, compared with the 4-valent gender-neutral vaccination programme over 100 years. These additional disease cases avoided would correspond to a 24, 36 and 48% cumulative incidence decrease in cervical cancer, CIN3 and CIN2 cases, respectively. It would also prevent additional 741 cervical cancer-related deaths over 100 years. A substantial additional reduction in cervical cancer and precancerous lesions burden is still observed when varying the vaccination coverage rate from 30 to 60% or reducing the duration of protection from lifelong to 20 years. Conclusions The switch to the 9-valent vaccine in Switzerland to prevent cervical diseases showed an important contribution in terms of public health impact compared with the 4-valent vaccine in an 11–26 years old gender-neutral population, even with very conservative assumptions such as low coverage rates or low duration of protection and limiting analysis to only cervical disease.