HPV vaccine efficacy in reducing HPV infections – Australia experience

In my 100 or more articles about the HPV vaccine, I spend as many words discussing HPV vaccine efficacy as I do about adverse events (which are extremely rare, despite the pseudoscientific claims of the anti-vaccine world). I keep reading comments and claims from the anti-vaccine religion that there is no “proof” that the HPV vaccine prevents infections and certainly no “proof” that it prevents cancer.

Well, a new article has been published that that describes how far HPV infection rates have dropped in Australia nine years after the implementation of HPV vaccination. Spoiler alert – the infection rate went way down, even though vaccine coverage is far from 100%.

Let’s take a look at this article, which provides us with more evidence in supporting the use of the HPV vaccine. HPV vaccine efficacy is corroborated by this new data.

All about HPV and Gardasil

Although 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 types of cancer. 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.

HPV vaccine efficacy paper

This study, by Dr. Dorothy A Machalek et al. of the Royal Women’s Hospital in Victoria, Australia and published in the Journal of Infectious Diseases, examined HPV vaccine efficacy by studying the impact of the quadrivalent HPV vaccine on HPV prevalence in Australia. The researchers studied the vaccine’s effect on HPV prevalence among women aged 18-35 in 2015.

Machalek et al. reported the longest surveillance follow-up to date and showed a continuous decline in the prevalence of vaccine-targeted HPV types among young women in Australia. Despite relatively low coverage by the HPV vaccine, women aged 25–35 also showed a significant fall in HPV infections.

The researchers found the following results:

  • Overall, three-dose vaccine coverage of the HPV vaccine in Australia was 53.3%.
  • Prevalence of the four HPV types included in the quadrivalent vaccine decreased from 22.7% in 2005-07 to 7.3% in 2010-12 to 1.5% in 2015 among women 18-24 years old. That is a 93.4% decrease in HPV types since the introduction of Gardasil in Australia.
  • But there’s more. The presence of the vaccine-preventable HPV types fell from 11.8% in 2005-07 to 1.1% in 2015 among women aged 25-35 years.

So, if you want scientific evidence that supports HPV vaccine efficacy, there can’t be much better out there. This study included hundreds of thousands of women and didn’t just show a minor reduction in the HPV infection risk, but a major, statistically significant one.

The authors concluded:

This study, which reports the longest surveillance follow-up to date shows that prevalence of vaccine-targeted HPV types has continued to decline among young women. A substantial fall also occurred in women aged 25–35, despite lower coverage within this age group. Strong herd protection, and the effectiveness of less than three-doses of the vaccine, have likely contributed to the size of these reductions.

Need I say more? A huge epidemiological study following women in Australia for nearly 10 years shows us a significant drop, almost a near elimination, of the vaccine-preventable HPV subtypes. Just to be clear, these are HPV subtypes that are causally linked to various cancers – reduce the HPV infection rate, reduce the cancer risk. Sounds like HPV vaccine efficacy is a substantiated fact.

There are so few ways to protect yourself against cancer. This is a major one. Get the Gardasil cancer-prevention vaccine for yourself and loved ones. Yes, call up your doctor and go. Right now.

Citations

The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor
Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!