This September, the Department of Health in the United Kingdom will begin a national programme of routine human papillomavirus immunisation of 12-13 year old schoolgirls, coupled with a two year catch-up campaign for those up to the age of 18 in 2009.1 The selected bivalent vaccine, Cervarix, protects against two of the most common human papillomavirus types that cause cervical cancer (types 16 and 18), whereas an available quadrivalent vaccine, Gardasil, also protects against two non-oncogenic types that cause genital warts (types 6 and 11). The linked study by Jit and colleagues from the Health Protection Agency (doi: 10.1136/bmj.a769) describes the mathematical modelling approach and results used to inform the Department of Health’s decision.2

Mathematical models are used to synthesise multiple data sources, to extrapolate short term clinical findings into long term outcomes of population level benefits and cost effectiveness, and to investigate the influence of uncertainties about data and alternative scenarios. The authors develop a dynamic model that reflects the sexual transmission of human papillomavirus infections (types 6, 11, 16, 18, and other high risk types). The model captures the direct benefits to girls who receive the vaccine and the indirect benefits to those who are not vaccinated, as a result of the reduced prevalence of human papillomavirus in the population—so called herd immunity. Unlike most other model based studies of human papillomavirus and cervical cancer, the authors analyse thousands of scenarios …