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Home » HPV vaccine efficacy in reducing HPV infections – Australia experience

HPV vaccine efficacy in reducing HPV infections – Australia experience

In the nearly 200 articles I have written 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

I know I cut and paste this section to every article I write about HPV vaccines, but it’s the first step to HPV vaccine myth debunking. Some readers may be coming here for the first time, and they ought to know just how the HPV vaccine prevents cancer. 

However, I try to update this section when necessary with new information about either the disease or the vaccine. 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 strains, 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.

Photo by Srikant Sahoo on Unsplash

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.



Michael Simpson
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