Viruses cause over 20% of cancer cases worldwide — and it should be celebrated that we have vaccines that can prevent some of those cancers. Considering the fear that many people have of cancer, getting these vaccines should be a high priority.
Part of the reason that these cancer vaccines are not a high priority is probably that cancer may not appear until long after the viral infection. If cancer appeared soon after the virus attacks, the cause and effect would be very clear, probably making the vaccine a much higher priority.
This article is going to focus on preventative cancer vaccines. There are cancer vaccines that are being developed as treatments for cancer — for example, there is a new mRNA vaccine that may be useful in treating colorectal cancer.
These “cancer vaccines” train the immune system, much like preventative vaccines, to attack existent cancer but they cannot prevent it. Furthermore, these types of vaccines are individually designed for each patient — in essence, unique antigens on the cancer cell surface are isolated and used to induce the immune system to attack the cancer cells. It’s a therapeutic technique that will still be used in conjunction with surgery and other adjuvant therapies like chemotherapy.
I might discuss this type of “cancer vaccines” more in the future as they become more prevalent, but for this article, I am going to be discussing preventative cancer vaccines.
Cancer-causing viruses
Of the 22 distinct families of viruses, five of these families are called “persisting,” because the virus remains in the body for life. One example is the varicella-zoster virus which causes chickenpox in children. However, it persists in the body and can reappear later in life in a more dangerous form called shingles.
Seven known viruses can cause cancer:
- Human papillomavirus (HPV) — causes cervical, oropharyngeal, anal, penile, vulvar, and vaginal cancers. And HPV may be linked to some forms of prostate and skin cancer.
- Epstein-Barr virus — causes Hodgkin lymphomas
- Human T-lymphotropic virus — causes adult T-cell leukemia
- Kaposi’s sarcoma-associated herpesvirus — causes Kaposi sarcoma
- Merkel cell polyomavirus — causes Merkel cell carcinoma
- Hepatitis B virus — causes hepatocellular carcinoma
- Hepatitis C virus — causes Hepatocellular carcinoma
All of these viruses, except for the two hepatitis viruses, are members of persistent virus families. These persistent viruses contain genetic code that teaches cells how to avoid cell death. This leads to immortalizing those infected cells and promoting cell growth, important characteristics of cancer. The cancer cells that develop from these viruses contain not only the original genetic code for the cell, but also include genetic code from the virus itself.
Just to be clear, only a small proportion of people who are infected by one of these persistent viruses will develop cancer associated with it. But this is true for almost all carcinogens — you will never find that 100% of individuals who have been exposed to a cancer-causing agent will develop cancer.
The other two viruses, hepatitis B and hepatitis C, are different than the persisting viruses. Most individuals’ immune systems can fight the infection and eventually eliminate the virus. However, some people are not able to fight the infection, possibly because of a suppressed immune system, long-term infections can cause extensive damage to the liver. These people have a higher risk of developing a type of liver cancer called hepatocellular carcinoma because the body’s attempts to repair the damaged liver cells increase the chance of a cancer-related mutation in the genetic code. As opposed to persisting viruses, the viruses themselves do not cause the liver cells to become immortal or promote cell growth.
These cancers are dangerous:
- Hepatocellular carcinoma kills over 700,000 people across the world every year. It is the third-deadliest cancer worldwide, and approximately 75% of those who die have had one of the two hepatitis infections.
- HPV is believed to cause nearly 5% of all new cancers across the world, making it almost as dangerous as tobacco in that respect. According to the CDC, roughly 79 million Americans are infected with HPV – approximately 14 million Americans contract a new HPV every year. Most individuals don’t even know they have the infection until the onset of cancer. The CDC also states that over 46,000 HPV-related cancers are diagnosed in the USA every year. It may be several times that amount worldwide. Over 311,000 women worldwide die each year from cervical cancer, almost all of which are caused by HPV.
These cancers are dangerous and deadly. But here is the thing — they are preventable.
Cancer-preventing vaccines
We can prevent these hepatitis- and HPV-related cancers with readily available, safe, and effective vaccines.
Merck manufactures Gardasil, which was first approved in 2006, probably the most popular HPV vaccine in the world. The first version of the vaccine, quadrivalent Gardasil, targets the two HPV genotypes known to cause about 70% of cervical cancer and two other HPV genotypes that cause genital warts. In Europe and other markets, Gardasil is known as Silgard.
The newer Gardasil 9, approved by the FDA in 2014, is a 9-valent vaccine, protecting against HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58. It targets the four HPV strains found in the quadrivalent version, along with five additional ones that are linked to cervical and other HPV-related cancers. Both versions of Gardasil are prophylactic, meant to be given to females or males before they become exposed to possible HPV infection through intimate contact.
Despite the claims of the anti-vaccine world, like the misinformation from Robert F Kennedy Jr, the HPV vaccine is extremely safe and extremely effective. Cervical cancer rates have dropped precipitously in countries that have broad coverage from the HPV vaccine.
The hepatitis B vaccine has been was introduced in 1986 and was recognized as the first anti-cancer vaccine. Like the HPV vaccine, it is extremely safe and extremely effective. Unfortunately, like the HPV vaccine, there has been a lot of anti-vaccine disinformation about the hepatitis B vaccine, almost all of it false.
I have written that there are just a handful of ways to prevent cancer — consuming a daily dose of kale-blueberry smoothies is not going to reduce your risk of cancer. However, the cancer-preventing vaccines, for HPV and hepatitis B, can substantially reduce your risk of some dangerous and deadly cancers.
I don’t understand any level of vaccine resistance, but it has gotten worse during this pandemic. However, given the fear of cancer in people, I don’t quite understand why people would refuse surefire prevention to a large number of cancers.
Citations
- Arbyn M, Weiderpass E, Bruni L, de Sanjosé S, Saraiya M, Ferlay J, Bray F. Estimates of incidence and mortality of cervical cancer in 2018: a worldwide analysis. Lancet Glob Health. 2020 Feb;8(2):e191-e203. doi: 10.1016/S2214-109X(19)30482-6. Epub 2019 Dec 4. Erratum in: Lancet Glob Health. 2022 Jan;10(1):e41. PMID: 31812369; PMCID: PMC7025157.
- de Martel C, Ferlay J, Franceschi S, Vignat J, Bray F, Forman D, Plummer M. Global burden of cancers attributable to infections in 2008: a review and synthetic analysis. Lancet Oncol. 2012 Jun;13(6):607-15. doi: 10.1016/S1470-2045(12)70137-7. Epub 2012 May 9. PMID: 22575588.
- Hofmann M, Thimme R. Kill, control, or escape: Immune responses in viral hepatitis. Clin Liver Dis (Hoboken). 2016 Oct 2;8(3):79-82. doi: 10.1002/cld.576. PMID: 31041069; PMCID: PMC6490199.
- White MK, Pagano JS, Khalili K. Viruses and human cancers: a long road of discovery of molecular paradigms. Clin Microbiol Rev. 2014 Jul;27(3):463-81. doi: 10.1128/CMR.00124-13. PMID: 24982317; PMCID: PMC4135891.
- Zhang X, Guan L, Tian H, Zeng Z, Chen J, Huang D, Sun J, Guo J, Cui H, Li Y. Risk Factors and Prevention of Viral Hepatitis-Related Hepatocellular Carcinoma. Front Oncol. 2021 Sep 9;11:686962. doi: 10.3389/fonc.2021.686962. PMID: 34568017; PMCID: PMC8458967.
