**Author details**

and actual effects on health-care cost consumption. Monitoring the impact of vaccination on type-specific infection could be important as it is the earliest change that could be anticipated, and failure to detect protection from infection will indicate failure to impact cancer in the decades that follow and allow appropriate changes in strategy to be introduced. As countries differ in their health-care priorities and infrastructure as well as in their incidence and prevalence of various HPV infections, their HPV vaccination strategies are also likely to differ [168]. As has been mentioned, the waning in the levels of HPV antibodies post-vaccination appears to plateau after 5 years. It is not known whether waning of HPV antibody levels in the longer term will require a vaccine booster. In addition, antibody correlates of protection have not been defined because there have so far been almost no cases of vaccination failure. If a reliable immunological correlate of protection can be identified, this will help in assessing the requirement for booster vaccinations and greatly facilitate the evaluation of second-

76 Human Papillomavirus and Related Diseases – From Bench to Bedside A Diagnostic and Preventive Perspective

As the type-specific prevalence of HPV infection is very high in young sexually active populations, the effect of a successful HPV vaccination programme should be detected quite rapidly by sentinel surveillance in these populations. The specific design of these sentinel studies will vary, but selecting clinics offering sexual counselling may be more efficient than school-based sampling. Reduction in the prevalence of types targeted by the vaccines as well as no increase in the prevalence of non-vaccine types are important end-points. Baseline data are needed to establish prevaccine prevalence as well as to determine the sample size required to observe impact beyond confidence intervals of sampling and testing errors. It is imperative that all HPV DNA prevalence surveys are performed using testing methodology that has been subjected to an international quality assurance, as comparability of data between countries or

Screening remains an important strategy in cervical cancer control in the HPV vaccination era. Women who have received HPV vaccination should continue regular screening, as cases of HGAs and invasive cervical cancer among vaccinated women have been reported [169]. There is also a concern whether the protective effect of adolescent vaccination has an impact on the incidence of cervical cancer when the vaccinated cohort reaches older age. It is reassuring to see evidence that, in well informed communities, there appears to be no change in women's attitude toward continual screening [170]. Furthermore, screening remains the only effective method for cervical cancer prevention for women who opt out of vaccination. However, reduction in the incidence of HGAs in young women following adolescent mass HPV vaccination supports a strategy to delay screening to a later age than the current practice of

Evidence from meta-analysis has overwhelmingly demonstrated the superiority in sensitivity of HPV DNA test over cytology in cervical cancer screening. Indeed, retrospective analysis of invasive cervical cancer tissues in well screened populations showed that more than 80% of cases were related to HPV-16 or HPV-18 [171]. With elimination of HPV-16 and HPV-18 with mass vaccination, the remaining oncogenic subtypes of HPV, which have low neoplastic transformation rates, should significantly lower the incidence of HGAs. The sensitivity and positive predictive value of cytologic screening will be further compromised [172]. The

generation vaccines.

even before *versus* after will otherwise not be possible.

starting screening once the girl becomes sexually active.

Fátima Galán-Sánchez and Manuel Rodríguez-Iglesias

Department of Microbiology, School of Medicine and Clinical Microbiology Laboratory, Puerta del Mar Univ. Hosp. University of Cádiz, Spain
