Kate Soldan

Evaluating the effectiveness of the human papillomavirus vaccination programme in England, using a regression discontinuity design

Abstract Background In England, the national human papillomavirus (HPV) immunization programme was introduced in 2008 to prevent cervical cancer. Girls aged 12–13 years were offered routine vaccination and those aged 14–18 years in 2008 were offered ‘catch-up’ vaccination. We evaluate the effect of the HPV catch-up vaccination programmes on cervical cancer and cervical dysplasia diagnoses, and provide an estimate of the vaccine effectiveness. Methods Using the 2011 Census, Hospital Episode Statistics, and mortality data for the population of England, we exploit the cut-off in eligibility and apply a regression discontinuity design to assess the impact of HPV vaccination on cervical disease. Results Vaccination reduced the incidence of cervical dysplasia and cancer diagnoses by 31% and 75%, respectively, at ages 23–30 years in girls offered catch-up vaccination at ages 17–18 years compared with those who were just above the eligibility age for the catch-up vaccination, with a clear discontinuity. Reductions continued amongst girls offered routine vaccination. Conclusion These estimates, obtained by using a quasi-experimental approach, are similar to vaccine effectiveness estimates based on more traditional approaches. This 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.

The impact of catch-up bivalent human papillomavirus vaccination on cervical screening outcomes: an observational study from the English HPV primary screening pilot

Abstract Background In England, bivalent vaccination (Cervarix) against high-risk human papillomavirus (HR-HPV) genotypes 16/18 was offered in a population-based catch-up campaign in 2008–2010 to girls aged 14–17 years. These women are now entering the national cervical screening programme. We determined the impact of catch-up bivalent vaccination on their screening outcomes. Methods We studied the overall and genotype-specific screening outcomes in 108,138 women aged 24–25 (offered vaccination) and 26–29 years (not offered vaccination) included in the English HPV screening pilot between 2013 and 2018. Results At 24–25 years, the detection of high-grade cervical intraepithelial neoplasia (CIN2+) associated with HPV16/18 decreased from 3 to 1% (p < 0.001), with estimated vaccine effectiveness of 87% (95% CI: 82–91%). The detection of any CIN2+ halved from 6 to 3% (p < 0.001), with an estimated vaccine effectiveness of 72% (95% CI: 66–77%). The positive predictive value of a colposcopy for CIN2+ decreased for both low-grade (p < 0.001) and high-grade (p = 0.02) abnormalities on triage cytology. The decreases in screen-detected abnormalities at age 26-29 were of a substantially smaller magnitude. Conclusions These data confirm high effectiveness of bivalent HPV vaccination delivered through a population-based catch-up campaign in England. These findings add to the rationale for extending screening intervals for vaccinated cohorts.