The perception of health benefits of vaccinesSince the end of the 18thcentury with the English doctor Edward Jenner, and especially one century later with the seminal works of French biologist Louis Pasteur, vaccination has proven its efficacy against some deadly infectious diseases. While some people might still object and dispute the positive benefits of vaccination, there is undeniable evidence to prove them wrong.
How do vaccines work?Vaccination works through stimulation of the vaccinated organism’s immune system. The goal of anti-infectious vaccination is to produce antibodies that fight virus and/or bacteria. The immune system gets trained to recognize and destroy such harmful agents. In the recent years, doctors have begun considering the possibility of not only treating cancer, but also preventing it by using vaccines.1
Can vaccines prevent cancer?According to the World Health Organization, around 15% of all cancers in the world are attributed to chronic infections. These infections are caused by Helicobacter pylori (gastric cancer), human papilloma virus (or HPV – cervix carcinoma, anal and oral cancer), hepatitis B and C virus (liver cancer), and, in some parts of the world, Epstein-Barr virus (certain types of lymphomas). The principle is quite simple: if we can prevent these chronic infections through vaccination, we will prevent the consequence of these chronic infections, i.e., cancers. This is used when healthy subjects are given cancer prevention vaccines, which will protect the body from disease-causing viruses. Certain cancer prevention vaccines are already available against some carcinogenic viruses, such as hepatitis B or HPV. The recently published epidemiologic results have proven their efficacy. Just take a look at Australia; as early as 2007, Australia began providing the HPV vaccine to all the 12 to 13 year-old girls for free, and started doing the same for all boys in 2013. According to official data, the HPV rate among young women was reduced from 22 percent to 1 percent between 2005 and 2015. Furthermore, according to Michaela T. Hall’s recent article in TheLancet Public Health, HPV infection (and cervical cancers) should be completely eliminated within the next 20 years. Australia is on track to becoming the first country to eliminate cervical cancer, according to Karen Canfell, a cancer epidemiologist at Cancer Council NSW.
Vaccines and immunotherapyBesides using prevention vaccines, cancer immunotherapy is an example for using cancer therapeutic vaccines, also known as therapeutic vaccines, which include other types of vaccines against the cancers not related to infections. Treatment vaccines are given to patients already diagnosed with cancer, and they are complementary to other treatments, such as chemotherapy or radiation therapy. We now know that all cancer cells harbor specific antigens on their surface, and these antigens are quite specific to the cancer type. The goal of all the ongoing research is to elicit a specific immune reaction directed to these specific antigens. The final aim is the immune destruction of all these cancer cells. Some vaccines have already shown some efficacy, especially for metastatic melanoma.
Outlook: what does the future bring?Currently in different stages of development, a lot of vaccines are still only available through clinical trials, partly because it is extremely hard to develop cancer treatment vaccines that are fully successful. There are still certain limitations, which the cancer treatment vaccines have to deal with, such as the often suppressed immune system in cancer patients, or the inadequacy of the immune system to recognize and subsequently destroy harmful cells – since cancer cells develop from an individual’s own healthy cells, the immune system may overlook healthy cells undergone changes.
Vaccination during cancer therapyMany cancer specialists will recommend avoiding infectious vaccination during cancer therapy (chemo or radiation therapy) for two main reasons. The first one is quite obvious, as these cancer treatments will decrease the efficiency of the immune system as collateral “side effects.” Therefore, it is quite useless to seek the elicitation of immune response through vaccination during these periods; the final result could be quite disappointing. The second reason is linked to the fact that some vaccines use a live, attenuated form of the virus. Even in its “attenuated” form, the virus can reveal itself to be dangerous inside an organism with a weakened immune system. It is beyond doubt that within the upcoming years we will see the emergence of new targeted therapies, and the development of new vaccines that, either alone or combined with existing therapies, will give new hopes to millions of cancer patients around the world. Sources:
- Conquer Cancer Foundation
- The dawn of vaccines for cancer prevention. Olivera Finn, Nature Reviews Immunology volume 18, pages 183–194, 2018
- The Projected timeframe until cervical cancer elimination in Australia: a modeling study. Michaela T Hall, Karen Canfell et al. Published October 02, 2018