HPV vaccination leads to decrease of anogenital warts and precancerous lesions of the cervix uteri in young women with low vaccination rates: a retrospective cohort analysis

Background: Although the human papillomavirus (HPV) vaccine has been recommended in Germany for girls since 2007, no organised vaccination programme was introduced and HPV vaccine coverage remains low. We investigated the HPV vaccination rates from 2008 to 2018 and the effects of HPV vaccination on anogenital warts and precancerous lesions in young women in Bavaria, Germany, a state with low vaccination rates. Methods: Retrospective analyses of claims data from the Bavarian Association of Statutory Health Insurance Physicians (KVB) on females born between 1990 and 2009 (9 to 28 years old in 2018) were conducted to calculate vaccination rates by birth cohort, proportion of vaccine types administered and incidence of anogenital warts and precancerous lesions of the cervix uteri. 942 841 Bavarian females 9 to 28 years old with available information on HPV vaccination were included to calculate vaccination rates. For the outcome analyses, data from 433 346 females 19 to 28 years old were analysed. Hazard ratios (HR) were computed from univariable and multivariable Cox regression models comparing vaccinated and unvaccinated women, considering type of vaccine used and contraceptive prescription. Results: 40·9% of 18-year-olds and only 13·3% of 12-year-olds were fully vaccinated in 2018 in Bavaria. Gardasil® and Gardasil9® were most commonly administered. Vaccinated compared to unvaccinated women had a lower incidence of anogenital warts and cervical lesions, however only small differences were detected between fully and partially vaccinated women. Fully vaccinated women had a 63% (HR 0·37 (95% confidence interval (CI) 0·34 to 0·40) and 23% (HR 0·77, 95%CI 0·71 to 0·84) lower risk of anogenital warts and cervical lesions, respectively. Women who were prescribed contraceptives prior to vaccination had a 49% higher risk of developing anogenital warts (HR 1·49, 95%CI 1·25 to 1·79) or cervical lesions (HR 1·49, 95%CI 1·27 to 1·75) compared to vaccinated women without contraceptive prescription. Conclusions: The evaluation of the effects of HPV vaccination in Bavaria showed a promising decline of anogenital warts and precancerous lesions in vaccinated young women. However, an increase in vaccination rates is necessary to achieve a greater population impact in preventing HPV-related diseases.