Epidemiology of genital human papillomavirus infections

Health service utilisation for anogenital warts in Ontario, Canada prior to the human papillomavirus (HPV) vaccine programme introduction: a retrospective longitudinal population-based study

OBJECTIVE

Trends in occurrence of anogenital warts (AGWs) can provide early evidence of human papillomavirus (HPV) vaccination programme impact on preventing HPV infection and HPV-induced lesions. The objective of this study was to provide a baseline of AGW epidemiology in Ontario prior to the introduction of the publicly-funded school-based HPV vaccination programme in September 2007.

SETTING AND PARTICIPANTS

As a retrospective longitudinal population-based study, we used health administrative data as a proxy to estimate incident AGWs and total health service utilisation (HSU) for AGWs for all Ontario residents 15 years and older with valid health cards between 1 April 2003 and 31 March 2007.

OUTCOME MEASURES

The outcome of interest was AGW healthcare utilisation identified using the International Classification of Diseases, 10th revision (ICD-10) diagnostic code for AGWs, as well as an algorithm for identifying AGW physician office visits in a database with a unique system of diagnostic and procedural codes. An AGW case was considered incident if preceded by 12 months without HSU for AGWs. Time trends by age group and sex were analysed.

RESULTS

Between fiscal years 2003 and 2006, we identified 123,247 health service visits for AGWs by 51,436 Ontario residents 15 years and older. Incident AGWs peaked in females and males in the 21-23 year age group, at 3.74 per 1000 and 2.81 per 1000, respectively. HSU for AGWs peaked in females and males within the 21-23 year age group, at 9.34 per 1000 and 7.22 per 1000, respectively.

CONCLUSIONS

To the best of our knowledge, this is the first population-based study of AGW incidence and HSU in Ontario. The sex and age distribution of individuals with incident and prevalent AGWs in Ontario was similar to that of other provinces before HPV vaccine programme implementation in Canada.

Modelling the population-level impact of vaccination on the transmission of human papillomavirus type 16 in Australia

BACKGROUND

Vaccines are now available to prevent the development of cervical cancer from genital human papillomavirus (HPV) infection. The decision to vaccinate depends on a vaccine's cost-effectiveness. A rigorous cost-effectiveness model for vaccinated individuals is presented in a companion paper; this paper investigates the additional benefits the community might receive from herd immunity.

METHODS

A mathematical model was developed to estimate the impact of a prophylactic vaccine on transmission of HPV type 16 in Australia. The model was used to estimate the expected reduction in HPV incidence and prevalence as a result of vaccination, the time required to achieve these reductions, and the coverage required for elimination. The modelled population was stratified according to age, gender, level of sexual activity and HPV infection status using a differential equation formulation. Clinical trials show that the vaccine is highly effective at preventing persistent infection and pre-cancerous lesions. These trials do not, however, provide conclusive evidence that infection is prevented altogether. The possible modes of vaccine action were investigated to see how vaccination might change the conclusions.

RESULTS

The model predicts that vaccination of 80% of 12-year-old girls will eventually reduce HPV 16 prevalence by 60-100% in vaccinated and 7-31% in unvaccinated females. If 80% of boys are also vaccinated, reductions will be 74-100% in vaccinated and 86-96% in unvaccinated females. A campaign covering only 12-year-old girls would require 5-7 years to achieve 50% of the eventual reduction. With a catch-up campaign covering 13-26-year-olds, this delay would be reduced to only 2 years. Unrealistically high coverage in both sexes would be required to eliminate HPV 16 from the population. Under pessimistic assumptions about the duration of vaccine-conferred immunity, HPV 16 incidence is predicted to rise in some older age groups.

CONCLUSIONS

Mass vaccination with a highly effective vaccine against HPV 16 has the potential to substantially reduce the incidence and prevalence of infection. Catch-up vaccination offers the potential to substantially reduce the delay before the benefits of vaccination are observed. A booster vaccination might be required to prevent an increase in incidence of infection in women over 25 years of age.

Lifestyle and socio-demographic factors associated with high-risk HPV infection in UK women

The world age-standardised prevalence of high-risk HPV (hrHPV) infection among 5038 UK women aged 20–59 years, with a low-grade smear during 1999–2002, assessed for eligibility for TOMBOLA (Trial Of Management of Borderline and Other Low-grade Abnormal smears) was 34.2%. High-risk HPV prevalence decreased with increasing age, from 61% at ages 20–24 years to 14–15% in those over 50 years. The age-standardised prevalence was 15.1, 30.7 and 52.7%, respectively, in women with a current normal, borderline nuclear abnormalities (BNA) and mild smear. In overall multivariate analyses, tertiary education, previous pregnancy and childbirth were associated with reduced hrHPV infection risk. Risk of infection was increased in non-white women, women not married/cohabiting, hormonal contraceptives users and current smokers. In stratified analyses, current smear status and age remained associated with hrHPV infection. Data of this type are relevant to the debate on human papillomavirus (HPV) testing in screening and development of HPV vaccination programmes.

comparison of two commercial assays for detection of human papillomavirus (HPV) in cervical scrape specimens: validation of the Roche AMPLICOR HPV test as a means to screen for HPV genotypes associated with a higher risk of cervical disorders

Certain high-risk (HR) human papillomavirus (HPV) types are a necessary cause for the development of cervical disorders. Women with persistent HR HPV infections have an increased risk of developing high-grade cervical lesions, compared with those who have no or low-risk HPV infections. Therefore, implementation of HPV detection into cervical screening programs might identify women at risk of cervical cancer. Several HPV detection methods with different sensitivities and specificities are available. Recently, a new PCR-based technique, the Roche AMPLICOR HPV Test, was developed. This test recognizes a group of 13 HR HPV types simultaneously. This study was undertaken to validate and compare HPV detection in 573 cervical scrape specimens by the AMPLICOR HPV Test and the INNO-LiPA HPV detection/genotyping assay (SPF10-LiPA system version 1). Human beta-globin was not detected in nine specimens, which were therefore excluded from the comparison. Eleven scrape specimens containing HPV type 53 or 66 were also excluded from the comparison because these (probably) HR HPV types cannot be detected by the AMPLICOR HPV Test. The results of HPV detection by the Roche AMPLICOR HPV Test were confirmed by INNO-LiPA HPV detection/genotyping assay in 539/553 cases, showing an absolute agreement of 97.5% with a Cohen's kappa of 0.9327, indicating almost complete similarity of the two tests. Like the INNO-LiPA HPV detection/genotyping assay, the AMPLICOR HPV Test was sensitive, specific, feasible, and easy to handle. The value of the Roche AMPLICOR HPV Test with a broad-spectrum HR HPV detection has to be determined in prospective clinical studies.

Fluctuations in prevalence of cervical human papillomavirus in women frequently sampled during a single menstrual cycle

In the last few years much attention has been focused on the implementation of human papillomavirus detection in population based screening programmes to identify women at risk for cervical cancer. Short-term fluctuations in prevalence of human papillomavirus were investigated within a single menstrual cycle. The highest prevalence was found at the follicular phase (55%), whereas the cumulative prevalence was 75%.