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The evidence is clear. HPV virus like particle (VLP) vaccines are highly effective in preventing persistent HPV infection and related cervical disease in girls and women naïve to the relevant HPV type(s). However, what remains unclear is the public health benefit (PHB) to be derived from vaccination of mid adult women 24-45: the age cohort considered in the study by Munoz et al1. Here's why:
In the trial, the vaccine efficacy (VE) in the per-protocol population was 90% for disease or infection related to HPV 6, 11, 16, and 18. VE is the appropriate metric to answer the focused question of whether the vaccine is able to prevent infection and disease in women naïve to the relevant HPV type. However this is not the best metric to evaluate the PHB of vaccination. To assess PHB, a different cohort, disease endpoint and metric may be considered.
Recent data provide evidence that new HPV infections in older, sexually-experienced women carry only a low risk of developing into CIN2+. 2 In the Munoz study, 25 “cases” of persistent HPV-16 and/or HPV-18 persistent infection or disease (largely CIN1) were averted in almost 4000 person-years of follow-up. If 10% of these infections would have been expected to develop into CIN2 or worse, then the extrapolated PHB of vaccinating women 24-45 would be prevention of 1.33 cases of CIN2+/1000 women over two years.
HPV vaccination is expensive. It is clear that targeting young women prior to sexual debut will provide the greatest benefit from HPV vaccination for a given cost. The peak of CIN2/3 occurs in women in their late-20's and early 30's---HPV vaccination must precede the acquisition of those causal HPV infections that occurred 5-10 years earlier.3 PHB and cost-effectiveness, not just VE, should be considered before establishing vaccination recommendations.
Disclosures: AH, MS, SW and DS are investigators for the NCI sponsored Costa Rican Vaccine Trial. GalaxoSmithKline provided vaccine and support for aspects of the trial associated with FDA regulatory submission needs.