Finally, there were a total of 5 cases of leukaemia (4 exposed to 9vHPV and 1 exposed to qHPV) in a clinical safety database with 13,360 exposed to 9vHPV. There is a potential concern that the number of observed cases in the study populations could be greater than expected. It is acknowledged that the time to onset in 4-5 cases is prolonged (482-1285 days); however leukaemia may have a prolonged latent phase prior to clinical manifestation of symptoms. Data from the post-marketing experience with qHPV do not show evidence of a signal for leukaemia. However, due to the potential prolonged latency prior to presentation coupled with the underreporting inherent in passive surveillance systems, this might not be unexpected. Multiple reports generally show that infant vaccinations may reduce the risk of subsequent childhood leukaemia. However, these studies have been limited to vaccinations received by infants and young children in routine immunisation programs. There appears to be no report involving older children /adolescents and human papilloma virus vaccination.
Of the five cases of leukaemia, three cases were diagnosed as acute leukaemia and were reported in subjects less than 20 years of age at diagnosis in the 9vHPV groups of studies 001 and 002 (a total of 12,319 person-years) with a time to onset of 27, 482 and 705 days post-dose 3.
Background leukaemia incidence rates are fairly consistent across geographic regions. A reasonable lower and upper bound of acute leukaemia incidence (lymphoid and myeloid combined) in the 10-20 yearold age is approximately 2 to 4 per 100,000 person-years. Two of the cases below 20 years of age were acute myeloid leukaemia, while acute lymphoblastic leukaemia is expected to be the most common type in this age group. Time of onset is not very informative for causality assessment for this type of outcome, since long induction times have to be expected.
通常10歳から20歳までの急性白血病の発症率は、10万人あたり2～4人であり、9価ガーダシルでは13360人接種して5人が発症した。（10万人あたり37人発症したことになる）
実は僕は9価ワクチンに期待している。日本人に多いHR型HPVにも有効だから。最終報告で安全性に問題がないと報告あり。対照群にinactive placebo である生食を使用していない。既存ワクチンと比較して免疫原性が高く、副反応が起こりやすいかもしれないが、杞憂であってほしい。
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