There is no link between vaccines and tumours
There is no proof that vaccines can cause cancer. There is evidence that some vaccinations (hepatitis B vaccine and Papilloma Virus vaccine) play an important role in preventing cancer. There are great expectations for the future use of vaccines against other types of cancer.
Some websites claim that there is a link between vaccines and tumours. It has been put forward, without sound scientific facts, that some types of cancer such as leukaemia and non-Hodgkin's lymphomas in children may be caused by mass vaccination.
Scientific elements refuting a causal link between vaccines and tumours
All tumours originate from a cell. In normal tissues, cells reproduce by dividing, in order to meet the various needs of the organism, such as coping with a greater requirement in terms of quantity of cells in the body or of "cell quality" for tissue differentiation, or to replace dead cells or those that, when damaged, undergo a process of programmed death called apoptosis.
In tumours, this delicate balance, which is governed by chemical messages sent from one cell to another and by the genes found in their DNA, is compromised. The cell continues to constantly reproduce and even the programmed death processes fail. At the origin of all of these phenomena are genetic alterations, called mutations, which, when combined, shut down the control mechanisms. It is not sufficient, in fact, for only one mechanism to be defective, errors must accumulate on different fronts in order for the tumour to start to develop.
Some of these mutations are hereditary, while others are caused by external factors. At any one time, mutations potentially capable of evolving into full-blown neoplasm originate and develop in tissues. It is estimated that there are up to 50 mutant clones per cm2 of exposed skin.
It is now well known that the immune system is capable of limiting the development and growth of tumours through a process called immunosurveillance. The immune response to tumours depends to a large extent on the effect on tumour cells of molecules which have no effect on normal cells of the same tissue and which have antigenic properties. As far back as 1943, Gross observed that when tumour cells were inoculated subcutaneously in mice with the same genetic constitution, they formed nodules that grew for a few days and then regressed. If the same tumour cells were reinoculated in these mice, they did not grow and did not give rise to the formation of nodules. The interpretation given to these results at that time was that the second inoculation of tumour cells did not give rise to the formation of a tumour since the mice had developed, during the first administration, a specific immune response against cancer cells (as if they had been vaccinated). Therefore, associating vaccination with the possible development of tumours not only goes against every theory, but the claim is refuted by a multitude of field trials and contradicts the normal and physiological actions of our immune system. It is currently known that in many human cancers neoplastic cells differ from normal ones, not because they possess antigens which are completely specific to the tumour, but because they have antigens on their surface present in normal cells only in particular phases of differentiation or in particular tissues. Against these proteins, collectively referred to as tumour-associated antigens (TAA, Tumour Associated Antigen), an immune response can develop. In fact, in the blood of patients with tumours, there are lymphocytes capable of recognising proteins derived from these antigens and activating against them.
As immunosurveillance theory posits, the number of potential tumours would be much higher than those that reach clinical observation if the immune system did not intervene to stop them. This claim would explain the higher incidence of tumours in immunosuppressed people compared to healthy ones1-2-3-4. It has also been shown in patients with cancer that the tumour itself can promote a state of immunosuppression which, in turn, facilitates the progression of cancer; that is, the tumour cells create a micro-environment capable of protecting the tumour from attack by the immune system5.
Let us now consider the causes of tumours and the epidemiology of the tumours that, in advanced countries, account for the second-highest cause of death (22.3%) after cardiovascular disease. Sixty-five percent of tumours stem from environmental causes, which in theory can be eliminated: dietary habits, social habits, cigarette smoking, exposure to toxic substances from industry and agriculture, etc.6
The International Agency for Research on Cancer (IARC) is the body responsible for evaluating all currently recognised carcinogens. In table 4, of the most recent report6, vaccines are not present among the approximately hundred carcinogens that have sufficient evidence of carcinogenicity in humans. Furthermore, even if we take into account carcinogens for which there is limited evidence of carcinogenicity in humans we find no hypothesis of carcinogenicity linked to vaccines.
There is, however, a proven link between "B lymphocyte" tumours and EBV (Epstein-Barr Virus) infection, as there are links between other viral infections such as Kaposi's sarcoma, associated with Human Herpesvirus 8 (HHV-8), hepatitis B virus and liver cancer, Human Papilloma virus (HPV) and cervical cancer.
In contrast to this, vaccinations have already been successfully used to fight cancer. This is the case of the hepatitis B vaccination which is drastically reducing the number of deaths from liver cancer, and the use of the Papilloma Virus (anti HPV) vaccine in Italy and Europe which will reduce the number of deaths from cervical cancer and probably other cancers associated with the virus. Moreover, there are expectations for other vaccines against cancer. For example, in Italy, researchers from the research centre in Experimental Medicine (Cerms) of the Molinette hospital in Turin have developed a vaccine that inhibits the progression of pancreatic cancer, one of the most aggressive neoplasms of all solid tumours and one that that kills numerous victims7 This study, which is about to be published in the prestigious international scientific journal Gastroenterology, lays the foundation for a new therapeutic strategy for this tumour, based on DNA vaccination, with the real possibility of extending the life of patients who were previously facing certain death.
There is no proof that vaccines can cause cancer. There is evidence that some vaccines (hepatitis B vaccine and Papilloma Virus vaccine) play an important role in preventing cancer. There are great expectations for the future use of vaccines against other types of cancer.
Sources / Bibliography
- Fischer A.Human primary immunodeficiency diseases.Immunity2007; 27:835-45
- Oertel SH, Riess H.Immunosurveillance, immunodeficiency and lymphoproliferations. RecentResults Cancer Res 2002; 159:1-8
- Grulich AE, van Leeuwen MT, Falster MO, etal.Incidence of cancers in people with HIV/AIDS compared with immunosuppressed transplant recipients: a meta-analysis.Lancet 2007; 370:59-67 24
- Tran H, Nourse J, Hall S, et al.Immunodeficiency-associated lymphomas.Blood Review
- Stewart TJ, Abrams SI.How tumours escape mass destruction.Oncogene 2008; 27:5894-5903
- Vincent James Cogliano e al.: Preventable Exposures Associated With Human Cancers. J Natl Cancer Inst. 2011 December 21; 103(24): 1827–1839.