The nearly indisputable evidence of the safety and effectiveness of the HPV vaccine is now supported by powerful evidence that the risk of cervical cancer is greatly reduced by the vaccine. We knew that the vaccine prevented many of the HPV types that were linked to cervical cancer, but it took time for us to observe a concomitant decrease in cases of cervical cancer.
Now, we have that evidence.
Let’s take a look at that study, which I know our favorite anti-vaxxers will dismiss, but maybe it will convince one parent to protect their children from future cases of cervical cancer.
All about HPV and HPV vaccines
I know I add this section to every article I write about HPV vaccines. It is updated almost every time with additional information about HPV or the vaccine. Moreover, there are new readers who want to know more about HPV, and this section can help someone get up-to-speed quickly. If you’ve read this section 47 times, just skip down to the next section where I discuss the key point of this article.
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 43,000 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 43,000 cancers a year in the USA alone. The HPV vaccine prevents becoming infected by HPV, which means you are protected from these cancers.
HPV vaccine and cervical cancer paper
Jiayao Lei, Ph.D. and colleagues, in a paper published in the New England Journal of Medicine on October 1, 2020, examined the risk of invasive cervical cancer in 1,672,983 Swedish women who received the quadrivalent HPV vaccine compared to those who did not. This cohort study included an open population of girls and women 10 to 30 years of age who were living in Sweden from 2006 through 2017.
The results can be summed up with this one graphic:
But, of course, we should review the most important results from this study:
- The study population included 1,672,983 girls and women 10 to 30 years of age, 527,871 of whom received at least one dose of HPV vaccine during the study period. Of the vaccinated group, 438,939 (83.2%) initiated vaccination before the age of 17 years.
- During the study period, cervical cancer was diagnosed in 19 women who had received the quadrivalent HPV vaccine, and in 538 women who had not received the vaccine – just the raw numbers show an incredible difference in the risks of cervical cancer.
- The cumulative incidence of cervical cancer increased rapidly at 23 years old because this is the age when Swedish women first participate in cervical cancer screening programs.
- At 30 years of age, the cumulative incidence of cervical cancer was 94 per 100,000 in unvaccinated women and 47 per 100,000 in vaccinated.
- Among women who initiated their HPV vaccination at the age of 17-30 years, the cumulative incidence was 54 per 100,00.
- Among women who initiated the vaccination before the age of 17, the cumulative incidence was 4 cases per 100,000. That is almost a 96% decrease in the risk of cervical cancer in those women who get the HPV vaccine early over those who are unvaccinated.
- After adjusting for age at follow-up, all vaccinated women had a 49% decrease in the risk of cervical cancer over unvaccinated women.
- After fully adjusting for age and other factors, women who were vaccinated before the age of 17 showed an 88% decrease in the risk of cervical cancer compared to unvaccinated women.
The authors concluded that:
In this large, nationwide study of girls and young women 10 to 30 years of age who had been vaccinated through HPV vaccination programs, we found that HPV vaccination was associated with a substantially reduced risk of invasive cervical cancer.
Summary
The evidence that the HPV vaccine not only prevents HPV infection but also subsequent cervical cancer is overwhelming in this huge study. There are so few ways to prevent any of the hundreds of different cancers, the easy-to-get, relatively inexpensive HPV vaccine should be the first choice of everyone.
The HPV vaccine is incredibly safe, so the benefits for it in preventing cancer (indeed, beyond cervical cancer) is overwhelming. Protect yourself and your children from cancer – get this vaccine!
Citations
- Lei J, Ploner A, Elfström KM, Wang J, Roth A, Fang F, Sundström K, Dillner J, Sparén P. HPV Vaccination and the Risk of Invasive Cervical Cancer. N Engl J Med. 2020 Oct 1;383(14):1340-1348. doi: 10.1056/NEJMoa1917338. PMID: 32997908.
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