An important role of the immune system is in the surveillance for abnormal or transformed cells, which is known as cancer immunosurveillance. Through this process, the first changes to normal tissue homeostasis caused by infectious or other inflammatory insults can be detected by the immune system through the recognition of antigenic molecules (including tumour antigens) expressed by abnormal cells. However, as they develop, tumour cells can acquire antigenic and other changes that allow them to escape elimination by the immune system. To bias this process towards elimination, immunosurveillance can be improved by the administration of vaccines based on tumour antigens. Therapeutic cancer vaccines have been extensively tested in patients with advanced cancer but have had little clinical success, which has been attributed to the immunosuppressive tumour microenvironment. Thus, the administration of preventive vaccines at pre-malignant stages of the disease holds promise, as they function before tumour-associated immune suppression is established. Accordingly, immunological and clinical studies are yielding impressive results.

免疫系统的重要作用是监视异常或转化的细胞，这被称为癌症免疫监视。通过该过程，由免疫系统通过识别异常细胞表达的抗原分子（包括肿瘤抗原）可以检测出由传染性或其他炎性损伤引起的正常组织稳态的最初变化。然而，随着肿瘤的发展，肿瘤细胞会获得抗原性和其他变化，从而使其逃避免疫系统的消除。为了使该过程趋向于消除，可以通过施用基于肿瘤抗原的疫苗来改善免疫监视。治疗性癌症疫苗已在晚期癌症患者中进行了广泛的测试，但在临床上几乎没有成功，这归因于免疫抑制性肿瘤微环境。因此，在疾病的恶性前期给予预防性疫苗是有希望的，因为它们在建立与肿瘤相关的免疫抑制之前就起作用了。因此，免疫学和临床研究产生了令人印象深刻的结果。