Benefits of catch-up in vaccination against human papillomavirus in medium- and low-income countries.

Human papillomavirus (HPV) vaccination of a birth cohort of girls in the 9-13 age range is recommended as a priority, but decreases in HPV vaccine cost may make catch-up of a few additional cohorts more attractive not only in high-income countries. We assessed the reduction in HPV16 and 18 infections that could be achieved in a medium- (Poland) and a low-income (Guinea) country by adding one-time catch-up of 12- to 19-year-old girls to the vaccination of 11-year-old girls. According to our ad hoc adapted dynamic model of HPV infection transmission, the addition of catch-up was estimated to bring forward the 50% reduction of HPV16/18 prevalence due to vaccination in women ≤35 by as much as 5 years. Catch-up of 12- to 15-year olds reduced the cumulative probability of HPV16/18 infections by age 35 in the relevant cohorts by about 30% in both countries. Catch-up of 16- to 19-year-old girls added little. Regardless of the chosen catch-up strategy, 16 to 20% of HPV16/18 prevention from vaccination was attributable to herd immunity. Assuming a sufficiently low vaccine cost, the addition of a catch-up round is, therefore, worth considering in medium/low-income countries to extend vaccine benefits to less young adolescent girls whose future access to cervical screening is uncertain.