Advances during the past 2-3 decades permitted the isolation and identification of a number of infectious agents causing specific wide-spread human cancers. During this period of time approximately 21 % of the global cancer incidence has been linked to infectious events. Besides a bacterial infection, Helicobacter pylori, causing the majority of gastric cancers, two types of viral infections with Hepatitis B virus (HBV) and high risk human papillomaviruses (HPV) (mainly types 16 and 18) have been identified. The former virus causing a substantial percentage of liver cancers, the latter being the predominant causes of cancer of the cervix, the second most frequent cancer in females on the global scale. Again in particular methods of genetic engineering permitted the development of vaccines against HBV and HPV infections. These vaccines can be considered as the first preventive cancer vaccines, obviously providing long-time protection against the respective forms of cancer. Applied globally in the respective age groups, jointly both vaccines have the potential to reduce the cancer burden in females by 12-15%, in males by 4-5%.
The novel mode of cancer prevention by vaccination encourages further research on a potential involvement of still other infections in cancers, not yet linked to exogenous agents. We are presently studying the putative role of novel viruses in cancers of the hematopoietic system and in gastrointestinal malignancies. Data from these studies will be presented as well as considerations how such infections could be prevented.