Elsevier

Vaccine

Volume 32, Issue 5, 23 January 2014, Pages 592-597
Vaccine

Human papillomavirus (HPV) vaccination coverage in young Australian women is higher than previously estimated: Independent estimates from a nationally representative mobile phone survey

https://doi.org/10.1016/j.vaccine.2013.11.075Get rights and content

Highlights

  • 2836 eligible women contacted (2.9% of numbers dialed) and 80.0% participated.

  • HPV vaccine coverage for HPV vaccine program age eligible adult women was 64/59/53% for dose 1/2/3.

  • Coverage was 9/14/21% higher than Register estimates after the catch up program.

  • In a validation substudy, 86% of self reported HPV vaccine doses were validated.

Abstract

Background

Accurate estimates of coverage are essential for estimating the population effectiveness of human papillomavirus (HPV) vaccination. Australia has a purpose built National HPV Vaccination Program Register for monitoring coverage, however notification of doses administered to young women in the community during the national catch-up program (2007–2009) was not compulsory. In 2011, we undertook a population-based mobile phone survey of young women to independently estimate HPV vaccination coverage.

Methods

Randomly generated mobile phone numbers were dialed to recruit women aged 22–30 (age eligible for HPV vaccination) to complete a computer assisted telephone interview. Consent was sought to validate self reported HPV vaccination status against the national register. Coverage rates were calculated based on self report and weighted to the age and state of residence structure of the Australian female population. These were compared with coverage estimates from the register using Australian Bureau of Statistics estimated resident populations as the denominator.

Results

Among the 1379 participants, the national estimate for self reported HPV vaccination coverage for doses 1/2/3, respectively, weighted for age and state of residence, was 64/59/53%. This compares with coverage of 55/45/32% and 49/40/28% based on register records, using 2007 and 2011 population data as the denominators respectively. Some significant differences in coverage between the states were identified. 20% (223) of women returned a consent form allowing validation of doses against the register and provider records: among these women 85.6% (538) of self reported doses were confirmed.

Conclusions

We confirmed that coverage rates for young women vaccinated in the community (at age 18–26 years) are underestimated by the national register and that under-notification is greater for second and third doses. Using 2011 population estimates, rather than estimates contemporaneous with the program rollout, reduces register-based coverage estimates further because of large population increases due to immigration since the program.

Introduction

In mid-2007 the Australian government introduced a National Human Papillomavirus (HPV) Vaccination Program. The prophylactic quadrivalent vaccine used prevents infection with HPV types 16 and 18, which are responsible for 70–80% of cervical cancers, as well as HPV types 6 and 11 which are responsible for almost all genital warts [1], [2]. For a limited two year period from July 2007 to December 2009, females aged 13–26 years were offered catch-up vaccination through schools, general practitioners (GPs) and other community based immunization providers [3]. The ongoing national program provides routine school based vaccination to 12–13 year old females and, from 2013, 12–13 year old males with a two year catch-up for males aged 14–15 years. The quadrivalent and bivalent HPV vaccines have been available on the private market in Australia since mid 2006 and mid 2007, respectively.

HPV vaccination coverage in Australia is routinely monitored using a purpose built register, the National HPV Vaccination Program Register, established by legislation as part of the program [3]. The Register collects notification of HPV vaccinations from immunization providers, with States and Territories routinely notifying all HPV vaccination episodes from their State school based programs. GPs and community based providers can report doses delivered to individuals through either paper based notifications, including print outs from practice software, or electronically as spreadsheets or via a secure web portal directly to the Register [3]. Throughout the two year female catch-up program GPs were paid $6 per notification as an incentive payment.

A good understanding of coverage levels is essential if the population effectiveness of HPV vaccination is to be estimated. However a one year delay between the commencement of the program and the establishment of the Register, and the fact that notifications from community providers were voluntary and required patient consent, suggest under-notification of doses for the adult women vaccinated in the community [4]. Available data from the Register show substantial variation in adult vaccine coverage recorded between States and Territories, suggesting that coverage data was more completely captured in the jurisdictions with existing state-based vaccination registers (e.g. Queensland); however an underlying difference in actual vaccination rates between jurisdictions cannot be excluded. New South Wales (NSW), which has the largest population, has reported coverage that is lower by 10–20% than the other populous Eastern states of Victoria and Queensland [4].

In 2011, we conducted a national computer assisted telephone interview (CATI) survey using random digit dialing of mobile phones of young women (aged 18–39 years) (the Young Women's Reproductive Health Survey). Here we present the findings for women eligible for HPV vaccination in the catch-up program with the aim of providing independent estimates of HPV vaccination coverage at a national and state level and comparing these results with those recorded in the Register.

Section snippets

Methods

Prior to undertaking the survey, we conducted a pilot study in March 2011 using the same method of dialing, which established the superiority of mobile phones over landlines as a means of randomly sampling young women in Australia [5]. We therefore conducted the coverage survey using random digit dialing of mobile phones with recruitment targets stratified by age and sex to ensure a representative sample with adequate power.

The CATI survey was conducted between August and December 2011 under a

Results

In the main study, 2836 eligible women were identified (2.9% of 97,463 numbers dialed) of whom 2269 completed an interview (participation rate 80.0%). Of the other numbers called, the most frequent outcomes were male respondent (23.8%), answering machine (22.3%), woman of ineligible age (16.0%), disconnected (15.4%), no answer (8.9%), engaged (8.0%) and business numbers (1.8%). Initial refusals before screening for eligibility occurred in 0.2% of cases. Taking into account calls to numbers

Discussion

Our estimates of HPV vaccination coverage amongst young adult women in Australia's 2007–2009 catch-up program of 64/59/53% for dose 1/2/3 are respectively 9/14/21% higher than estimated by the Register (using 2007 population estimates) immediately after the catch-up program. The discrepancy in estimates could be even higher, given the large increase in the estimated resident population of young women over time (Fig. 1). The survey confirms the under-reporting of doses administered in the

Disclosure

BD receives funding from bioCSL Pty Ltd and BD and JK receive funding from the Australian Government Department of Health for HPV surveillance. BD has received speaker's honoraria from Merck and SPMSD. JMLB and MS were partner investigators on an Australian Research Council Linkage Grant on which CSL was a partner organization. BL owns shares in bioCSL.

Acknowledgements

The authors thank staff at the National HPV Vaccination Program Register: Daniela Petrovski, Jennifer Ngyugen, Genevieve Chappell and Hunter Valley Research Foundation.

The National HPV Vaccination Program Register is owned by the Department of Health and Ageing and managed by VCS Inc. This study was funded by the Australian National Health and Medical Research Council (NHMRC) grant no. 568971 and the Victorian Cytology Service. BL, BD and JK are supported by NHMRC fellowships.

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