One of the misinformed tropes of the anti-vaccine world is that there is no evidence that the human papillomavirus (HPV) vaccine actually reduces cancer rates. Given that the vaccine was only introduced in the last 10 years, it would take time for researchers to study this issue. But now, we have more evidence that the cervical cancer rate declined after the introduction of the HPV vaccine in the USA.
We have robust evidence that the HPV vaccine actually stops HPV infections, which are linked to several types of cancer. Over the past few years, a number of published articles have provided us with powerful evidence that the HPV vaccine is significantly reducing the cervical cancer rate.
Although there is a myth that the HPV vaccine is just to prevent cervical cancer, I expect, over the next few years, there will be new research that shows reductions in other cancers, in both women and men, as a result of the introduction of the vaccine. Moreover, the effect of the vaccine on males may take longer since the vaccine was recommended for males only a few years after it was introduced.
This year, a solid systematic review, the most powerful research in the hierarchy of biomedical science, along with other studies, have been published that provide strong evidence that the HPV vaccine reduces the cervical cancer rate. Now we have a new study to add to the body of science supporting the effectiveness in preventing cancers of the HPV vaccine.
All about HPV vaccines
Genital and oral human papillomavirus (HPV) infections are the most common sexually transmitted infections (STI) in the USA. HPV is generally transmitted from personal contact during vaginal, anal or oral sex.
It’s important to note that there are more than 150 strains or subtypes of HPV that can infect humans – however, only 40 of these strains are linked to one or more different cancers. Of those 40 strain, most are fairly rare.
Although the early symptoms of HPV infections aren’t serious and many HPV infections resolve themselves without long-term harm, HPV infections are causally linked to many types of cancers in men and women. According to current medical research, here are some of the cancers that are linked to HPV:
In addition, there is some evidence that HPV infections are causally linked to skin and prostate cancers. The link to skin cancer is still preliminary, but there is much stronger evidence that HPV is linked to many prostate cancers.
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 31,500 HPV-related cancers are diagnosed in the USA every year. It may be several times that amount worldwide.
There were two HPV vaccines on the world market before 2014. GSK, also known as GlaxoSmithKline, produced Cervarix, a bivalent (protects against two HPV strains) vaccine. It has been withdrawn from the US market (although available in many other markets), because of the competition from the quadrivalent (immunizes against four different HPV strains) and 9-valent (against nine HPV strains) Gardasil vaccines.
Merck manufactures Gardasil, 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.
Gardasil is one of the easiest and best ways to prevent a few dangerous and, to abuse the definition slightly, common cancers that afflict men and women. Without a doubt, the HPV vaccine prevents cancer.
Currently, in the United States, the Advisory Committee on Immunization Practices (ACIP) recommends that preteen girls and boys aged 11 or 12 are vaccinated against HPV. The immunization is also recommended for teenage girls and young women up to the age of 26 who did not receive it when they were younger, and teenage boys and young men up to the age of 21.
Let me sum this all up so that if you come away from this section with nothing else, you get this summary. HPV is a sexually transmitted disease. HPV causes 31,500 cancers a year in the USA alone. The HPV vaccine prevents becoming infected by HPV, which means you are protected from these cancers.
Cervical cancer rate and HPV vaccine – new article
A new article by Fangjian Guo et al., published in the American Journal of Preventative Medicine, reported that the cervical cancer rate for young women fell after the HPV vaccine was introduced. The vaccine was introduced in 2006 in the USA, at first just for females.
The researchers analyzed 2001-14 data on 15-34-year-old females from the CDC National Program for Cancer Registries (NPCR) and the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) programs which closely track cancer rates in the USA. Combined data from NPCR and the SEER Program include cancer incidence and population data for all 50 states, the District of Columbia, and Puerto Rico, providing information on more than 24 million cancer cases.
The results were impressive. The average annual cervical cancer rate, for women aged 15-24 years, dropped from 8.4 per million during 2003-06, before the vaccine was introduced, to 6.0 per million during 2011-14. This represents a statistically significant 29% reduction in the cervical cancer risk. The authors also reported that the rates fell for both squamous cell carcinoma of the cervix (SCC) and non-SCC, and there was a sharp decline after 2009.
Two important points to consider:
- High-risk sexual behaviors did not appear to decline during this time period, so the falling cervical cancer rate can be attributed to HPV vaccines.
- HPV vaccine coverage has slowly increased over this period, though by 2013, it was still only 55% of girls. As coverage increases, there should be a more significant decrease in the cervical cancer rate.
The authors concluded that:
This study found a significant decrease in cervical cancer incidence among young females after HPV vaccine introduction. The observed strong decrease in cervical cancer incidence among young females aged 15–24 years is unlikely to result entirely from changes in cervical cancer screening, suggesting HPV vaccination is at least partially responsible for the reduction in cancer incidence. These findings serve as further evidence of the effectiveness of HPV vaccination in preventing cervical cancer.
This is important, because despite previous evidence of HPV vaccine effectiveness against HPV infections, genital warts, and cervical lesions, it is essential to know its effect on the target outcome, cervical cancer. Further research is needed to confirm these findings, which may include direct comparison of cervical cancer incidence between vaccinated and unvaccinated women in the U.S. and other countries, trends in cervical cancer incidence among young women in other countries with high HPV vaccine coverage, and HPV types in vaccinated and unvaccinated cervical cancer patients.
Summary
Despite the claims of the anti-vaccine zealots, who have a particular hatred for the HPV vaccine, there is powerful evidence that the vaccine is very safe and prevents cancer. The reduction in the cervical cancer rate in the USA, after the introduction of the HPV vaccine, is robust evidence that this vaccine should be given to every young man and woman.
The HPV vaccine is one of the most powerful tools in preventing cancer. Why would any parent not give this vaccine to their children?
Citations
- Guo F, Cofie LE, Berenson AB. Cervical Cancer Incidence in Young U.S. Females After Human Papillomavirus Vaccine Introduction. Am J Prev Med. 2018 Aug;55(2):197-204. doi: 10.1016/j.amepre.2018.03.013. Epub 2018 May 30. PubMed PMID: 29859731; PubMed Central PMCID: PMC6054889.
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