Impact of a population-based HPV vaccination program on cervical abnormalities: a data linkage study

Abstract

BackgroundAustralia was one of the first countries to introduce a publicly funded national human papillomavirus (HPV) vaccination program that commenced in April 2007, using the quadrivalent HPV vaccine targeting 12- to 13-year-old girls on an ongoing basis. Two-year catch-up programs were offered to 14- to 17- year-old girls in schools and 18- to 26-year-old women in community-based settings. We present data from the school-based program on population-level vaccine effectiveness against cervical abnormalities in Victoria, Australia.MethodsData for women age-eligible for the HPV vaccination program were linked between the Victorian Cervical Cytology Registry and the National HPV Vaccination Program Register to create a cohort of screening women who were either vaccinated or unvaccinated. Entry into the cohort was 1 April 2007 or at first Pap test for women not already screening. Vaccine effectiveness (VE) and hazard ratios (HR) for cervical abnormalities by vaccination status between 1 April 2007 and 31 December 2011 were calculated using proportional hazards regression.ResultsThe study included 14,085 unvaccinated and 24,871 vaccinated women attending screening who were eligible for vaccination at school, 85.0% of whom had received three doses. Detection rates of histologically confirmed high-grade (HG) cervical abnormalities and high-grade cytology (HGC) were significantly lower for vaccinated women (any dose) (HG 4.8 per 1,000 person-years, HGC 11.9 per 1,000 person-years) compared with unvaccinated women (HG 6.4 per 1,000 person-years, HGC 15.3 per 1,000 person-years) HR 0.72 (95% CI 0.58 to 0.91) and HR 0.75 (95% CI 0.65 to 0.87), respectively. The HR for low-grade (LG) cytological abnormalities was 0.76 (95% CI 0.72 to 0.80). VE adjusted a priori for age at first screening, socioeconomic status and remoteness index, for women who were completely vaccinated, was greatest for CIN3+/AIS at 47.5% (95% CI 22.7 to 64.4) and 36.4% (95% CI 9.8 to 55.1) for women who received any dose of vaccine, and was negatively associated with age. For women who received only one or two doses of vaccine, HRs for HG histology were not significantly different from 1.0, although the number of outcomes was small.ConclusionA population-based HPV vaccination program in schools significantly reduced cervical abnormalities for vaccinated women within five years of implementation, with the greatest vaccine effectiveness observed for the youngest women.

The Early Benefits of Human Papillomavirus Vaccination on Cervical Dysplasia and Anogenital Warts

“…Our results of vaccine impact are generally consistent with previous research on cervical dysplasia. [17][18][19][20] Although all observational studies have reported more conservative estimates than randomized controlled trials, 7 this is not surprising given that trials estimated treatment effects under ideal conditions. This does, however, highlight the importance of observational studies in determining the real-world effectiveness of this vaccine.…”

“…In addition, low vaccine coverage may jeopardize the expected public health benefits and cost-effectiveness of qHPV vaccine programs. As there are currently few studies on the real-world effects of the qHPV vaccine [17][18][19][20][21] and none on the population-level impact of qHPV vaccine programs on the burden of disease, we undertook a populationbased, retrospective cohort study to assess the impact of the qHPV vaccine and Ontario's qHPV vaccination program on the incidence of cervical dysplasia and AGW among adolescent girls.…”

Comparing human papillomavirus vaccine knowledge and intentions among parents of boys and girls

“…It is important that clinicians strongly recommend vaccination of all adolescents at 11-12 y old and clearly explain to parents the necessity of protecting their teens well before potential HPV exposure, as this would result in greatest vaccine effectiveness. 35 Furthermore, vaccination of young adolescents induces higher antibody levels than vaccination at older ages. 36 Findings from the current analysis indicate parents whose teens received at least one dose of HPV vaccine were more likely to report agreement with statements about HPV vaccine safety and efficacy against a variety of health outcomes than parents of unvaccinated teens, and parents of unvaccinated teens who intended to vaccinate them in the future were more likely than parents who stated their teens would never be vaccinated to endorse these statements.…”

Evaluation of safety and immunogenicity of a quadrivalent human papillomavirus vaccine in healthy females between 9 and 26 years of age in Sub-Saharan Africa

“…24 Our observed safety findings are also similar to that of other studies, whereby vaccine recipients have higher rates of injection site pain, erythema and swelling, but similar rates of systemic AEs. 32 Given the high vaccine efficacy seen in the clinical trials, and the fact that in the 8 y since its original licensure, the qHPV vaccine has been shown to be highly effective at the population level, with marked reductions in the prevalence of HPV vaccine-type related infection and disease in many countries, [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] our findings suggest the vaccine should be equally effective in sub-Saharan African women.…”