Human papillomavirus 16/18 seroprevalence in unvaccinated women over 30years with normal cytology and with high grade cervical abnormalities in Australia: results from an observational study.

Louiza S Velentzis,Freddy Sitas,Karen Canfell,Dianne L O’Connell,Emily Banks,Rohit Sinha,Jessica Darlington-Brown,Sam Egger,Ian H Frazer

doi:10.1186/s12879-014-0676-z

Abstract

BackgroundAustralia commenced human papillomavirus (HPV) vaccination in 2007, with a two-year catch-up to the age of 26; catch-up cohorts are thus now entering their thirties. Plans for monitoring vaccine impact involve pre- and post-vaccination assessment of cervical HPV DNA in the general population and in high grade abnormalities. Although HPV serology is less sensitive than DNA genotyping, it assesses lifetime exposure and may be easier to measure in the general population. However, benchmark pre-vaccination seroprevalence of vaccine-included types in unvaccinated women with high grade abnormalities has not previously been reported.MethodsWe assessed seroprevalence for HPV16/18 from a population-based sample of 3,729 women with normal cytology and 971 women with confirmed high grade abnormalities (CIN2/3), aged 30–64 years, unvaccinated, and recruited in New South Wales in 2006–2010. We examined the variation in HPV16/18 seropositivity by age and in relation to a range of reproductive and behavioural characteristics in the subgroup of normal cytology women with no recent history of high grade cervical disease.ResultsThe HPV 16, 18 and combined seroprevalence was 19%, 7% and 24% among women with normal cytology, and 39%, 13% and 44% among women with CIN2/3, respectively. For both groups, HPV16/18 seroprevalence was highest at age 30–39 years and decreased with age. In multivariable analysis for women with normal cytology, HPV16 and HPV18 seropositivity were each associated with the number of lifetime sexual partners (p-trend <0.001 and 0.052, respectively) and for HPV16 this was also associated with age (p-trend <0.001) and prior diagnosis of Chlamydia (adjusted OR 1.89, 95% CI 1.27-2.80).ConclusionsThe findings of this study inform pre-vaccination estimates of HPV seropositivity in women with normal cytology and women with high grade abnormalities. Almost a quarter of unvaccinated women aged over 30 years with normal cytology, and more than 40% of those with CIN2/3, had seroconverted to HPV 16 or 18. These findings provide a potential additional benchmark for assessing the effects of HPV vaccination.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-014-0676-z) contains supplementary material, which is available to authorized users.

Highlights

Australia commenced human papillomavirus (HPV) vaccination in 2007, with a two-year catch-up to the age of 26; catch-up cohorts are entering their thirties
Indications of the effects of the National HPV Vaccination Program have already been observed in vaccinated young cohorts– these include a decline in the prevalence of cervical HPV DNA for vaccine-included types in women aged 18–24 years [3], substantial declines in the incidence and prevalence of high-grade abnormalities in women up to 25 years old [4,5] and a reduction in the risk of high grade cervical abnormalities in women who completed the vaccine series at the ages of 11–27 [6]
In Australia, we identified only one study [14], using a convenience sample of men and women aged up to 69 years which was limited by lack of information on cytology/histological status and on potential risk factors for HPV exposure, which might be important for monitoring outcomes in higher risk groups

Summary

Introduction

Australia commenced human papillomavirus (HPV) vaccination in 2007, with a two-year catch-up to the age of 26; catch-up cohorts are entering their thirties. Plans for monitoring vaccine impact involve pre- and post-vaccination assessment of cervical HPV DNA in the general population and in high grade abnormalities. The program involves routine vaccination of 12–13 year old girls at school, and until 2009 involved a school, General Practitioners and community “catch-up phase” for women aged up to 26 years. As initial vaccination cohorts are entering their thirties, the effects of vaccination in women over 30 years old can be evaluated

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