Abstract
BackgroundCurrent prophylactic vaccines against human papillomavirus (HPV) target two oncogenic types (16 and 18) that contribute to 70% of cervical cancer cases worldwide. Our objective was to quantify the range of additional benefits conferred by second-generation HPV prophylactic vaccines that are expected to expand protection to five additional oncogenic types (31, 33, 45, 52 and 58).MethodsA microsimulation model of HPV and cervical cancer calibrated to epidemiological data from two countries (Kenya and Uganda) was used to estimate reductions in lifetime risk of cervical cancer from the second-generation HPV vaccines. We explored the independent and joint impact of uncertain factors (i.e., distribution of HPV types, co-infection with multiple HPV types, and unidentifiable HPV types in cancer) and vaccine properties (i.e., cross-protection against non-targeted HPV types), compared against currently-available vaccines.ResultsAssuming complete uptake of the second-generation vaccine, reductions in lifetime cancer risk were 86.3% in Kenya and 91.8% in Uganda, representing an absolute increase in cervical cancer reduction of 26.1% in Kenya and 17.9% in Uganda, compared with complete uptake of current vaccines. The range of added benefits was 19.6% to 29.1% in Kenya and 14.0% to 19.5% in Uganda, depending on assumptions of cancers attributable to multiple HPV infections and unidentifiable HPV types. These effects were blunted in both countries when assuming vaccine cross-protection with both the current and second-generation vaccines.ConclusionSecond-generation HPV vaccines that protect against additional oncogenic HPV types have the potential to improve cervical cancer prevention. Co-infection with multiple HPV infections and unidentifiable HPV types can influence vaccine effectiveness, but the magnitude of effect may be moderated by vaccine cross-protective effects. These benefits must be weighed against the cost of the vaccines in future analyses.
Highlights
Prophylactic vaccines against human papillomavirus (HPV), responsible for all cervical cancers and a smaller proportion of other anogenital and oral cancers, represent one of the major breakthroughs in cancer prevention
The two currently available HPV vaccines, which target two of the most oncogenic types, HPV-16 and -18, have the potential to prevent about 70% of cervical cancer cases worldwide; the 4-valent vaccine targets two non-oncogenic types, HPV-6 and -11, responsible for genital warts
In settings that have not successfully implemented organized cervical cancer screening programs, the introduction of HPV vaccination may provide a critical opportunity for primary prevention of cervical cancer; in settings with organized screening, vaccination could provide the opportunity to reduce the intensity of screening programs
Summary
Prophylactic vaccines against human papillomavirus (HPV), responsible for all cervical cancers and a smaller proportion of other anogenital and oral cancers, represent one of the major breakthroughs in cancer prevention. The two currently available HPV vaccines, which target two of the most oncogenic types, HPV-16 and -18, have the potential to prevent about 70% of cervical cancer cases worldwide; the 4-valent vaccine targets two non-oncogenic types, HPV-6 and -11, responsible for genital warts. Given regional variation in the proportion of cervical cancers attributable to HPV-16 and -18, the maximum impact of vaccination may be lower than 70%. Current prophylactic vaccines against human papillomavirus (HPV) target two oncogenic types (16 and 18) that contribute to 70% of cervical cancer cases worldwide. Our objective was to quantify the range of additional benefits conferred by second-generation HPV prophylactic vaccines that are expected to expand protection to five additional oncogenic types (31, 33, 45, 52 and 58)
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