人類乳突瘤病毒（HPV）疫苗

HPV and cervical cancer related articles part V- HPV vaccine

HPV是一種可經由性行為感染的疾病，大多數人被感染後，無臨床症狀或症狀很輕微，而且都是暫時性的，身體的免疫系統會清除病毒。少部分人呈現持續性感染，成為女性子宮頸癌、陰道癌、外陰癌，男性陰莖癌，男女性肛門癌、咽喉癌、舌癌、扁桃腺癌等及良性肛門生殖器尖形濕疣（俗稱菜花）、良性複發呼吸道乳頭狀瘤等疾病之重要致病因子。被HPV感染後，哪些人是暫時性？哪些人是持續性？至今無法預期。HPV疫苗可以預防HPV感染，因此也可預防大多數宮頸癌和外陰癌等腫瘤；但對於已經存在的感染，並沒有加速清除病毒效能，對於該病毒引發之疾病，也沒有治療的效果。世界衛生組織（WHO）建議HPV疫苗接種的首要目標族群為年齡為9－14歲尚未有性經驗的女童及青少女。台灣於2018年底才開始針對國中入學女生（約12－13歲），全面公費施打HPV疫苗，起步稍晚。無論二價疫苗、四價疫苗、還是九價HPV疫苗之原始設計中，採用的病毒株範圍仍有限，無法涵蓋全部高危險型別病毒的預防，交叉保護也不穩定，若接種覆蓋率難以突破、群體保護力也受限，只能預防約七至九成HPV感染，期待HPV疫苗可以像消滅天花一樣徹底清除子宮頸癌，是有相當難度的。所以定期子宮頸癌篩檢仍有其必要性，以達到早期診斷、早期治療，降低子宮頸癌的發病率及死亡率。HPV疫苗注射後，常見的局部不良反應主要是注射部位疼痛、紅腫。常見的全身不良反應是發熱，其次是頭痛、噁心和疲勞。大部份人的不良反應都比較輕微，持續不超過4－5天，無需特殊治療。現階段，世界上大多數國家或地區接種HPV疫苗尚未普及，可視為過渡期，當HPV疫苗逐步推廣，接種覆蓋率逐漸增高，預估子宮頸癌前病變與子宮頸癌的發生率及盛行率也會逐漸降低，勢必衝擊現行的子宮頸抹片與病毒基因檢測。因此，後疫苗時代的子宮頸癌篩檢及防治策略，有待進一步釐清。近年來，有些先進國家採取男女無性別差異（gender neutral）之HPV疫苗接種策略，不再偏厚女性，鼓勵男性也開始全面接種，將可以克服HPV疫苗覆蓋率（coverage rate）偏低的瓶頸，預期可同步增加男女保護力，並發揮最大功效。

HPV is a sexually transmitted disease. Most people have been infected with noclinical symptoms or even mild and transient symptoms. The human immunesystem will finally eradicate the virus. However, a small number of peoplepresent persistent infections, resulting in cervical cancer, vaginal cancer, vulvarcancer, male penile cancer, male and female anal cancer, throat cancer, tonguecancer, tonsil cancer, benign anal-genital warts (condyloma acuminata) andrecurrent respiratory papillomatosis. So far, it is still unpredictable whether theHPV infection will become transient or persistent finally. The HPV vaccine canprevent HPV infection, and thus can prevent most HPV related tumors suchas cervical cancer and vulvar cancer. However, for existing HPV infections,the vaccines neither accelerate the elimination of virus in reality, nor treat thediseases caused by the virus in effect. The World Health Organization (WHO)recommends that the primary target group for HPV vaccination is girls andadolescent girls between the ages of 9 and 14, with no sexual experience. Atthe end of 2018, Taiwan began to target girls in the middle school (about 12-13 years old), and the HPV vaccine was applied at a public expense, eventhough unexpectedly delay. The original design of the bivalent, quadrivalent,and nonavalent HPV vaccines was limited in the range of virus strains. It is notenough to cover all high risk HPV types. The cross protection effect of HPVvaccines is unstable. If the vaccine coverage rate is difficult to break upward,the herd protection effect will also be limited. Presently, only about 70% to90% of HPV infections can be prevented. It is difficult to expect HPV vaccineto completely eliminate cervical cancer like the elimination of smallpox.Consequently, regular cervical cancer screening program seem to be stillnecessary to achieve early diagnosis, early treatment, and reduce the incidenceand mortality of cervical cancer. After HPV vaccine injection, the commonlocal adverse reactions are mainly pain and redness at the injection site. Acommon systemic adverse reaction is fever, followed by headache, nausea, andfatigue. Most people have milder adverse reactions that last no more than 4-5days without special treatment. At the present time, most countries or regions in the world have not yet been broadly vaccinated with HPV vaccine. It can be regardedas a transitional period. When the HPV vaccine is gradually promoted, the coverage rateis gradually increasing. The prevalence and incidence of cervical precancerous lesionsand cervical cancer will gradually reduce. However, it will also impact the current Papsmear and HPV testing programs. The screening strategy for cervical cancer preventionin the post-vaccine era will also need further clarification. Recently, the Gender-neutralvaccination strategy has been started and promoted. It is expected to improve theprotection of both women and men, while it maximizes benefits from vaccination at lowercoverage.