Abstract
BackgroundPersistent high-risk human papillomavirus (HPV) infection is endorsed by the World Health Organization as an intermediate endpoint for evaluating HPV vaccine effectiveness/efficacy. There are different approaches to estimate the vaccine effectiveness/efficacy against persistent HPV infections.MethodsWe performed a systematic literature search in Pubmed to identify statistical approaches that have been used to estimate the vaccine effectiveness/efficacy against persistent HPV infections. We applied these methods to data of a longitudinal observational study to assess their performance and compare the obtained vaccine effectiveness (VE) estimates.ResultsOur literature search identified four approaches: the conditional exact test for comparing two independent Poisson rates using a binomial distribution, Generalized Estimating Equations for Poisson regression, Prentice Williams and Peterson total time (PWP-TT) and Cox proportional hazards regression. These approaches differ regarding underlying assumptions and provide different effect measures. However, they provided similar effectiveness estimates against HPV16/18 and HPV31/33/45 persistent infections in a cohort of young women eligible for routine HPV vaccination (range VE 93.7–95.1% and 60.4–67.7%, respectively) and seemed robust to violations of underlying assumptions.ConclusionsAs the rate of subsequent infections increased in our observational cohort, we recommend PWP-TT as the optimal approach to estimate the vaccine effectiveness against persistent HPV infections in young women. Confirmation of our findings should be undertaken by applying these methods after longer follow-up in our study, as well as in different populations.
Highlights
Persistent high-risk human papillomavirus (HPV) infection is endorsed by the World Health Organization as an intermediate endpoint for evaluating HPV vaccine effectiveness/efficacy
Four were excluded because of the wrong publication type, seven because a lack of an actual vaccine effectiveness/efficacy calculation, and in four studies a different outcome other than the one of interest was reported, leaving a total of articles (32 randomized controlled trials and 2 observational cohort studies) for inclusion [13, 14, 16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46]. (Fig. 1) This resulted in analyses regarding vaccine efficacy/effectiveness of persistent HPV infections
Two methods provided an estimate of rate ratios either via Generalized Estimating Equations (GEE) using a Poisson model (n = 2), or via direct comparison of independent incidence rates using the Conditional exact method (n = 31) [47, 48], which assumes that the number of events from one group, given the total number of events in both groups, follows a binomial distribution under the null hypothesis using identical Poisson processes in the vaccinated and unvaccinated group [49]
Summary
Persistent high-risk human papillomavirus (HPV) infection is endorsed by the World Health Organization as an intermediate endpoint for evaluating HPV vaccine effectiveness/efficacy. Given its role in the pathogenesis, persistent hrHPV infection is endorsed by the World Health Organization (WHO) as an intermediate endpoint for estimating HPV vaccine effectiveness/efficacy in cervical and anal cancer among 16–26 year olds [5]. The risk for recurrent detection might be higher than developing a first-time infection [8] Another challenge is that rates of infection over time in young vaccinated cohorts might vary due to increasing sexual behavior in this age group [9]. This varying infection rate might influence which statistical approach is optimal for estimating vaccine efficacy/effectiveness in observational cohort studies
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