Abstract:
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Human papillomavirus (HPV) vaccines prevent anogenital disease caused by specific HPV types. The impact of HPV vaccination on the overall burden of disease, irrespective of HPV, is an important public health question. Attempts were made to use clinical trial data to assess such impact. However, the interpretation of vaccine efficacy (VE) on the endpoint of disease irrespective of HPV is not widely understood. We used the GARDASIL 9 clinical program as a case study to assess the value of measuring VE in such endpoint. The assessment used heuristic reasoning and probability calculations. VE in the irrespective of HPV endpoint is driven simultaneously in opposite directions by the high estimate of prophylactic efficacy and a numerically negative estimate of risk reduction that also reflects of high prophylactic efficacy in the absence of cross-protection. The VE estimate in the irrespective of HPV endpoint is ambiguous and difficult to interpret. Comparing this estimate across different HPV vaccine studies requires for each study an understanding of the contributions of vaccine HPV type efficacy and the incidence of disease not related to vaccine HPV types.
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