Evaluating the effectiveness of the HPV vaccination programme in England, using regression discontinuity design

Abstract

In England, the National human papillomavirus (HPV) immunisation programme was introduced in 2008 to prevent cervical cancer. Girls aged 12 to 13 were offered routine vaccination, and those aged 14 to 18 years in 2008 were offered 'catch-up' vaccination. Using Census 2011, Hospital Episode Statistics and mortality data for the population of England, we exploit the cut-off in eligibility and apply a regression discontinuity design (RDD) to assess the impact of HPV vaccination on cervical disease. Vaccination reduced the incidence of cervical dysplasia and cancer diagnoses by 31% and 75% respectively at ages 23 to 30 years in girls offered catch-up vaccination at ages 17 to 18 years compared to those who were just above the eligibility age for the catch-up vaccination, with a clear discontinuity. Reductions continued amongst girls offered routine vaccination. These estimates obtained with a quasi-experimental approach are similar to vaccine effectiveness estimates based on more traditional approaches. This novel approach provides further evidence of the HPV vaccination programme reducing adverse cervical outcomes in young women and could be used for future studies to evaluate major changes in HPV vaccination policy and for studies of longer-term outcomes including other cancers and deaths.