Vaccines have been a standard part of staying healthy for several decades. We know that vaccines are given to healthy people to help prevent diseases, such as mumps, measles, chickenpox and many others.
These vaccines are usually attenuated (weakened) or killed pathogens (like viruses or bacteria) and are given to train the immune system to defend the body against specific pathogens. The idea of a vaccine against cancer was spawned more than half a century ago and since then, a better understanding of the role of the immune system against cancer, improved diagnostics, better techniques and strategies for vaccine development have turned this ‘outrageous and far-fetched hypothesis’ into reality.
Currently, doctors treat cancer using surgery, radiation, chemotherapy or a combination of the three. These approaches, although life-saving, are aggressive, expensive, and can cause permanent harm or even death. A vaccine, on the other hand, would stimulate the immune system and potentially help the body kill the cancer cells. Cancer vaccines can either be preventive (or prophylactic) vaccines, which are intended to prevent cancer from developing in healthy people or treatment (or therapeutic) vaccines, which are intended to keep pre-cancerous lesions under control, treat an existing cancer or help keep it from coming back after other treatments by strengthening the body’s natural immune response against the cancer.
Cancer prevention vaccines stop cancer-causing viruses from infecting cells and block the process that may eventually result in cancer cell growth. These are the cancer prevention vaccines available worldwide:
Hepatitis B vaccine. The vaccine prevents the hepatitis B virus (HBV) infection which ranges in severity from a mild illness, lasting a few weeks, to a serious long-term illness that can lead to liver disease or liver cancer.
The world's first universal Hepatitis B vaccination program was launched in Taiwan in July 1984. There is evidence that the prevalence of Hepatitis B infection has been reduced remarkably to approximately one-tenth of the original prevalence and the incidence of liver cancer reduced in the vaccinated group. The vaccine has an excellent record of safety and effectiveness. Since 1982, over 1 billion doses of Hepatitis B vaccine have been used worldwide.
Human Papilloma Virus (HPV) Vaccine. HPV is a viral infection that is passed between people through skin-to-skin contact. Most infected people have no symptoms and are unaware they are infected. There are more than 100 varieties of HPV, of which at least 13 are cancer-causing. Cancers caused by HPV often do not show symptoms until the cancer is in later stages of growth.
Vaccines that treat existing cancer are known as therapeutic cancer vaccines. These are the cancer treatment vaccines available (though not in all countries) for prostate cancer, bladder cancer, melanoma skin cancer, kidney cancer, and non-small cell lung cancer:
Sipuleucel-T (Provenge) is the only vaccine approved by the US FDA to treat cancer. It is used to treat advanced prostate cancer that is no longer being helped by hormone therapy. For this vaccine, immune system cells are extracted from the patient’s blood and sent to a lab where they are exposed to chemicals that turn them into dendritic cells and a protein prostatic acid phosphatase(PAP).This allows them to produce an immune response against prostate cancer cells. The dendritic cells are then returned to the patient by infusion into a vein. Back in the body, the dendritic cells help other immune system cells attack the prostate cancer. Provenge lengthened median survival by 4.1 months, improved 3-year survival by 38% and reduced overall risk of death by 22.5%. Clinical trials are being done to investigate whether the vaccine can be used in men with less advanced prostate cancer.
Bacillus Calmette–Guérin (BCG) is a vaccine primarily used against tuberculosis. It is a live attenuated (weakened) vaccine, originally produced from the same bacterium that gives rise to bovine TB. Attenuation resulted in a loss of the gene producing virulence so that it could safely be inoculated into humans. The BCG vaccine was first used in 1921 and is very efficacious against tuberculosis meningitis, but the efficacy against pulmonary tuberculosis seems to vary with geography. It has been found to be effective in helping to prevent or delay bladder cancers from growing back or spreading into the deeper layers of the bladder. For melanoma patients, BCG boosts general immunity and can be directly injected into tumors of patients with stage III melanomas. The adjuvant immune therapy with BCG has also shown promising results for patients after surgical resection in advanced malignant melanoma.
Oncophage is a heat shock protein (HSP) vaccine made extracted from the patient’s tumours. The heat shock protein gp96 is an essential protein that regulates immunity. Oncophage has been studied in Phase 3 clinical trials for the treatment of kidney cancer and metastatic melanoma and is currently being investigated in a Phase 1/2 trial in recurrent glioma. Oncophage was approved in 2008 in Russia for the treatment of kidney cancer patients at intermediate risk for disease recurrence. It is not yet approved in the USA and the European Medicines Agencyis evaluating conditional approval for Oncophage.
CimaVax EGF is a vaccine being developed in Cuba for non-small cell lung cancer. The vaccine targets epidermal growth factor (EGF), a protein that is found naturally in the body that signals cells to grow and divide. Some cancers make the body produce excess amounts of EGF so the cells grow and divide uncontrollably. The vaccine works by stimulating the immune response to make antibodies recognize and bind to EGF and ultimately block the signal that tell the cancer cells to grow and divide, therefore, cancer growth slows down. In clinical trials, Cimavax- treated lung cancer patients who were younger than 60 years old and they survived an average of 18.5 months. The younger vaccinated patients survived significantly longer than controls, who survived an average of 7.6 months. A phase 3 trial is currently in progress in Cuba.
Vaccine researchers and academics are looking into ways to make vaccines trigger the immune system to attack cancer cells and boost the immune system’s response. Various other cancer vaccines have shown promise in clinical trials, but they are not yet approved. Clinical trials are underway to evaluate how well these vaccines treat other types of cancers, including brain tumors, breast cancer, cervical cancer, colorectal cancer, kidney cancer, lung cancer, lymphoma, melanoma, pancreatic cancer, and prostate cancer.
We anticipate a wave of cancer vaccine approvals in the next years, mainly due to recent advances in the clinical trials of cancer vaccines, the accelerated pace of research, and the increased funding for cancer research programs. The Hepatitis B vaccine and HPV vaccines have demonstrated reduction of the incidence of cancers related to the viruses. It is hoped that cancer vaccines will someday expand the number of cancer therapies.