Cancer prevention is a big business on the internet. A quick search will find someone hawking supplements or the new quinoa blueberry smoothie to prevent cancer. But from a scientific perspective, there’s really only a handful of ways to substantially reduce your risk of cancers. One of that handful of methods is to get the HPV vaccine that will reduce your risk of contracting HPV-related cancers.
Recently, a study examined the long-term trends of HPV-related cancers in Norway and estimated the number of cancer cases that could be prevented by HPV vaccines. This adds to the mountain of evidence that the HPV vaccine ought to be known as the “cancer-preventing HPV vaccine.” OK, I’m not good at naming vaccines.
Let’s talk a little about HPV, then tackle this new research.
All about HPV and Gardasil
Many of you have read this section an enormous number of times, however, for some of the readers of this blog, this article might be their first bit of research into the human papillomavirus (HPV) vaccine. Thus, it’s important to get a brief overview of HPV and the vaccines. If you’ve read this section before, just skip to the next section if you want.
Genital and oral 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. 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:
These are all dangerous and disfiguring cancers that can be mostly prevented by the HPV cancer vaccine. If you’re a male, and you think that these are mostly female cancers, penile cancer can lead to amputation of your penis. Just think about that guys.
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. Accordingly, about 27,000 HPV-related cancers are diagnosed in the USA every year.
There were two HPV vaccines on the world market before 2014. GSK, also known as GlaxoSmithKline manufactured Cervarix, a bivalent 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 subtypes) and 9-valent (against nine subtypes) 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. It targets the four HPV genotypes 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 before females or males become exposed to possible HPV infection through intimate contact.
Gardasil is one of the easiest and best ways to prevent a few deadly cancers that are related to HPV. It is definitely a cancer-preventing vaccine.
(Just a quick note. There are actually two cancer-preventing vaccines. Along with the HPV vaccines, the hepatitis B vaccine is also important for the prevention of some cancers. The vaccine prevents hepatitis B viral infections. Chronic hepatitis B infections can lead to liver cirrhosis or cancer. Liver cancer is actually one of the few cancers in the USA where the incidence has increased over the past few years. And if you follow the anti-vaccine rhetoric, you know the hepatitis B vaccine is almost as controversial as the HPV vaccine.)
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.
The Norwegian study of HPV-related cancers
In a study published in BMJ Open in February 2018, Bo T Hansen et al. wanted to examine the long-term incidence trends of HPV-related cancers from the Cancer Registry of Norway. From that data, the estimated the number of cancer cases that might be prevented by vaccines against HPV variants, especially 16/18/31/33/45/52/58, which are more closely linked to these cancers.
Just to make sure this is understood, a lot of good vaccine studies come from Nordic countries (Norway, Sweden, and Denmark especially), because they have a highly managed healthcare system. This makes it much easier to do epidemiological studies since healthcare information for every resident from birth to death is available through computer searches. So, if you want to search for HPV-related cancers, you can uncover detailed data.
The researchers examined the incidence, from 1953 to 2015, of HPV-related cancers. These cancers include squamous cell carcinomas (SCC) of the cervix, vulva, vagina, oropharynx, anus, and penis, along with adenocarcinoma of the cervix.
Here’s what they found:
- Among women, the incidences of the SCC of the anus, oropharynx, and vulva along with cervical adenocarcinoma increased from 1953-2015.
- The average annual percentage change for these HPV-related cancers in women was approximately +1.2.
- Among men during the same time period, SCC of the anus, oropharynx, and penis increased.
- The average annual percentage change for all male HPV-related cancers was somewhat higher +1.9.
- The authors estimated that a vaccine against HPV types 16 and 18 might prevent 402 cancers annually.
- On the other hand, they estimated that the HPV vaccine against types 16, 18, 31, 33, 45, 52, and 58 (which is covered by the 9-valent Gardasil which protects against HPV Types 6, 11, 16, 18, 31, 33, 45, 52, and 58) would prevent 478 HPV-related cancers annually.
If we translated these results to a larger population like the USA (Norway only has 5.233 million people), we could estimate that over 29,000 HPV-related cancers could be prevented every year (see Note 1).
The authors concluded that:
HPV vaccination can prevent a substantial number of cancers in Norway, in cervical and non-cervical organs, among women and men.
I know what the anti-vaccine religion will say – “so what, it doesn’t show actual cancer prevention.” I tire of this argument. We know that HPV infections are causally linked to certain cancers, but it takes time for cancer to develop. I think that many people believe that if you contracted HPV today, cancer starts tomorrow. That’s not how it works, it can be years or decades from the causal event before cancer can be detected. That was one of the reasons it took a long time to understand that smoking causes cancer because it took a lot of effort and time to uncover the link.
The causal link between certain HPV strains and certain cancers has been established a large and robust body of research. And it’s not from epidemiological studies, it’s from actual analysis of the pathophysiology of these cancers.
So, unless you wish to deny logic, it is clear that if you stop HPV infections, you will stop any cancer related to that infection. Of course, some time out into the future, 20-30 years after the HPV vaccine was released, we can do a study that will look at a population of HPV-vaccinated vs. unvaccinated adults, and examine the incidence of HPV-related cancers in both groups. And I’m sure that the results will be as predicted – those who had received the HPV vaccine were much less like to contract those cancers. And for then it will be too late for those who did not get the vaccine.
For those of you who have missed all the points above, let’s make this simple – the HPV vaccine prevents HPV-related cancers. Oh, let me make it even simpler – this vaccine saves lives.
- Yes, the 29,000 number is somewhat higher than the estimated 27,000 because it’s not appropriate to take epidemiological data from one study and try to apply it to another population. But I did for illustration purposes only.
- Hansen BT, Campbell S, Nygård M. Long-term incidence trends of HPV-related cancers, and cases preventable by HPV vaccination: a registry-based study in Norway. BMJ Open. 2018 Feb 23;8(2):e019005. doi: 10.1136/bmjopen-2017-019005. PubMed PMID: 29476028; PubMed Central PMCID: PMC5855252.