In fact, one in six cancer cases worldwide is caused by a known infectious agent, with the proportion rising to one-third in some countries in Sub-Saharan Africa. The four main culprits are hepatitis B and C (hepB and hepC), human papillomavirus (HPV), and Helicobacter pylori, which are collectively responsible for 1.9 million cases of liver, cervical, and gastric cancer annually.
疫苗和癌症之间的联系常常被忽视，这是第二个普遍存在的误解：光是命运（或许还有吸烟）决定了谁得癌症。事实上，全世界六分之一的癌症是由已知致病因子造成的，在撒哈拉以南的一些非洲国家，这一比例高达三分之一。四大主要致病因子是乙肝和丙肝、人类乳突病毒（HPV）以及幽门螺旋杆菌四者加起来每年造成190万例肝癌、子宫癌和胃癌病例。