Abstract
SummaryBackgroundHealth equality is increasingly being considered alongside overall health gain when assessing public health interventions. However, the trade-off between the direct effects of vaccination and herd immunity could lead to unintuitive consequences for the distribution of disease burden within a population. We used a transmission dynamic model of human papillomavirus (HPV) to investigate the effect of ethnic disparities in vaccine and cervical screening uptake on inequality in disease incidence in England.MethodsWe developed an individual-based model of HPV transmission and disease, parameterising it with the latest data for sexual behaviour (from National Survey of Sexual Attitudes and Lifestyles [Natsal-3]) and vaccine and screening uptake by ethnicity (from Public Health England [PHE]) and fitting it to data for HPV prevalence (from ARTISTIC, PHE, Natsal-3) and HPV-related disease incidence (from National Cancer Registry [ONS]). The outcome of interest was the age-adjusted incidence of HPV-related cancer (both cervical and non-cervical) in all women in England in view of differences and changes in vaccination and screening uptake by ethnicity in England, over time. We also studied three potential public health interventions aimed at reducing inequality in HPV-related disease incidence: increasing uptake in black and Asian females to match that in whites for vaccination; cervical screening in women who turn 25 in 2018 or later; and cervical screening in all ages.FindingsIn the pre-vaccination era, before 2008, women from ethnic minorities in England reported a disproportionate share of cervical disease. Our model suggests that Asian women were 1·7 times (95% credibility interval [CI] 1·1–2·7) more likely to be diagnosed with cervical cancer than white women (22·8 vs 13·4 cases per 100 000 women). Because HPV vaccination uptake is lower in ethnic minorities, we predict an initial widening of this gap, with cervical cancer incidence in Asian women up to 2·5 times higher (95% CI 1·3–4·8) than in white women 20 years after vaccine introduction (corresponding to an additional 10·8 [95% CI 10·1–11·5] cases every year). In time, we predict that herd immunity benefits will diffuse from the larger white sub-population and the disparity will narrow. Increased cervical screening uptake in vaccinated women from ethnic minorities would lead to rapid improvement in equality with parity in incidence after 20 years of HPV vaccination.InterpretationOur study suggests that the introduction of HPV vaccination in England will initially widen a pre-existing disparity in the incidence of HPV-related cancer by ethnicity, partly due to herd immunity disproportionately benefiting subgroups with high vaccination rates. Although in time this induced disparity will narrow, increasing cervical screening uptake in girls from ethnic minorities should be encouraged to eliminate the inequality in cervical cancer incidence in the medium term. We recommend that dynamic effects should be considered when estimating the effect of public health programmes on equality.FundingCancer Research UK.
Highlights
human papillomavirus (HPV) infection is implicated in more than 99% of cervical cancer cases[1] with roughly 70% caused by types HPV-16 and HPV-18.2 Since 2006, two highly effective prophylactic vaccines against HPV-16 and HPV-18 have been available worldwide[3] and cervical screening remains an effective secondary prevention strategy
Interpretation Our study suggests that the introduction of HPV vaccination in England will initially widen a preexisting disparity in the incidence of HPV-related cancer by ethnicity, partly due to herd immunity disproportionately benefiting subgroups with high vaccination rates
We show that increasing cervical screening uptake among vaccinated girls from ethnic minorities could eliminate the inequality in cervical cancer incidence within 30 years
Summary
HPV infection is implicated in more than 99% of cervical cancer cases[1] with roughly 70% caused by types HPV-16 and HPV-18.2 Since 2006, two highly effective prophylactic vaccines against HPV-16 and HPV-18 have been available worldwide[3] and cervical screening remains an effective secondary prevention strategy. In 2008, the UK initiated school-based vaccination of 12–13 year-old-girls, with more than 86% of girls receiving a full course of vaccination between 2012 and 2014.4 findings of demographic studies have consistently reported substantially higher levels of vaccination uptake in white girls than in those from minority ethnic backgrounds.[5,6] An equivalent disparity is reported in cervical screening attendance: white women are more than twice as likely to have attended screening as women of another ethnic origin.[7,8] a positive association has been recorded between uptake of vaccination and of cervical cancer screening in both empirical[9,10] and survey-based[5,9] studies in the UK. Findings of a recent study have shown clear patterns of so-called www.thelancet.com/public-health Vol 3 January 2018
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