As rates of HPV-related cancers increase, why are people refusing the vaccine?

When we think about sexually transmitted diseases (STDs), things that usually come to mind include AIDS, syphilis, or gonorrhoea. But the most commonly transmitted STD in the US and globally is actually one that can cause oropharyngeal, anal, penile, and cervical cancer — Human papillomavirus (HPV).¹ ² The virus is transmitted through vaginal, anal, or oral sex. But even skin-to-skin genital contact without penetrative sex can lead to transmission.³ ⁴

It's so prevalent that about 80% of sexually active people will be infected by the virus at some point in time in their lives. In 2017, it was estimated that approximately 79 million Americans had HPV, and this number was expected to increase by 14 million each year.⁵

Dangerous types of HPV

Fortunately, 70-90% of HPV infections can be cleared by the immune system.⁶

In such cases, the person may remain asymptomatic and not even be aware of the infection. This is because only about 14 of over 150 HPV strains are cancer-causing⁷ ⁸ and types 16, 18, 31, and 33 are the most common amongst these "high-risk" strains.

When the body's immune system is unable to fight them off, the viral DNA mixes with the infected person's DNA. It then disrupts the cell's division process and leads to cancer.

Even though the harmful types of HPV form a small minority of the many strains, it doesn't mean that they're uncommon. According to a 2017 report by the Centers for Disease Control and Prevention (CDC), 22.7% of American adults aged 18-59 had high-risk genital HPV, while 1 in 25 had high-risk oral HPV.⁹

In total, these HPV infections cause 5% of all cancers worldwide, and the numbers are increasing every year. The CDC has reported that there were 30,115 new cases of HPV-associated cancers in 1999, but this number has gone up to 43,371 in 2015.¹⁰

HPV-related cervical cancer

Of all the different cancers, the relationship between HPV and cervical cancer is the most well-researched as the association has been established since the 1980s.¹¹ HPV16 and HPV18 are responsible for 70% of global cervical cancer cases (which is the 4th most common cancer among females).¹² ¹³ Researchers estimate that approximately 570,000 women were diagnosed with cervical cancer globally in 2018, and about 311,000 die from the disease every year.¹⁴

Fortunately, a vaccine has been developed to target HPV-related cervical cancer. And it's proven to be very effective. A Swedish study conducted over 11 years (2006-2017) has shown that there’s almost a 90% reduction in cervical cancer cases for those vaccinated compared to the unvaccinated group.¹⁵

Within the US, the vaccine has also been available for use around a similar period and it has been effective at lowering incidence rates. Between 1999 to 2015, cervical cancer cases have decreased by 1.6% each year.¹⁶

Non-cervical HPV cancers rates are increasing rapidly

While progress has been made with HPV-related cervical cancer, the rise of other types of cancer cases is what's worrying medical experts.

In more recent decades, it was discovered that HPV can lead to anal and penile cancer. It’s currently estimated that over 90% of anal cancers and 60% of penile cancers are due to the virus.¹⁷ What’s more, a recent study in 2020 found that anal cancer rates in the US are increasing by nearly 3% every year — which is faster than many other types of cancer.¹⁸

HPV infections are also the cause of many head and neck cancers as well — particularly in the oropharynx (back of the throat). In such cases, oral sex is the mode of transmission.¹⁹

In the past, the highest risk factors of head and neck cancers were traditionally alcohol and tobacco use. But with strong public health campaigns discouraging the use of these substances, there was a steady decline in such cases.²⁰

The flipside to this is that HPV-related head and neck cancers have now started to creep up over the years.

Approximately 75% of oropharyngeal cancers are due to HPV infections, and its incidence rate in men has even surpassed the rate of cervical cancer in women within the US.²¹ ²²

The CDC has also reported that between the period of 1999 to 2015, oropharyngeal cancers rates increased by 2.7% per year in men and 0.8% in women.

The usual profile of people with head and neck cancers is no longer just older individuals who smoke or drink alcohol frequently. It's now also affecting young, educated people of higher socioeconomic status with little exposure to tobacco and alcohol.²³

How changing sexual habits increased HPV transmission

A large part of why we're seeing increased HPV cancer rates is a result of people's changing sexual habits. The sexual revolution of the 1960s saw more people having multiple sexual partners and oral sex became less of a taboo.²⁴ Little did the youth of that era know that they were increasing the chances of HPV transmission.

A group of researchers has found that people who engage in oral sex are 80% more likely to develop oropharyngeal cancer. And this was particularly so for those that have multiple oral sex partners and had their first encounter before 18 years old.²⁵

White males have the greatest number of oral sex partners throughout their lifetime compared to other racial demographics. So this could explain why the incidence rate of oropharyngeal cancer is higher in this group.²⁶

Similarly, for cervical and anal cancer, the behavioural risk factors for these diseases also include having a high number of sexual partners for both men and women.²⁷ ²⁸

Protection from HPV is available, but people aren't aware of it

Another major cause of the increasing rates of HPV cancers is the lack of public awareness about the disease, who it affects, and how to prevent infections. And this is particularly so for men.

A 2019 survey of 6,000+ Americans aged 18-26 years old found that 70% of respondents didn’t know that HPV can result in oral, anal, and penile cancers. And the researchers also found significant gender differences.

For example, 60% of men versus 32% of women were unaware the HPV causes cervical cancer. Even the percentage of men who did not know that HPV causes penile cancer was higher compared to women (89% vs. 78%).²⁹

Fewer men were also aware of the HPV vaccine compared to women (53% vs. 79%).

This big difference in HPV awareness between males and females is because the virus has been historically associated with cervical cancer. Early vaccination campaigns largely targeted women. And as a result, perceptions that it's mainly a women's health issue still persist — even in medical circles.³⁰

Many physicians still hold onto these outdated notions because it was what they learned in medical school at the time. So many do not sufficiently educate sexually active male patients about HPV and the available vaccine. Most men only become aware of the virus after they’ve developed cancer.³¹

Prevention and early detection is key

Vaccination is the clear answer, but only half of Americans are getting it 

The current HPV vaccine used in the US targets 9 high-risk strains, and it's been shown to be highly efficacious. It can help prevent up to 90% of cervical cancers and is also recommended for protecting against anal and oropharyngeal cancer.³² ³³ ³⁴

A key feature of the vaccine is that it's a preventative measure, and taking it before any sexual activity has started is crucial. It does not work as a cure once a person has been infected. And this is why the CDC currently recommends children between 11-12 years old to receive the jab.³⁵ ³⁶

But despite its effectiveness, the US is far from reaching its 80% vaccination goal. A 2019 report states that only about 44% of boys and 53% of girls have been vaccinated.³⁷ If it’s so effective, why are only 50% of Americans who are eligible for it coming forward for the jab?³⁸

It's often been assumed that parents avoid vaccinating their children because they're worried it might promote youth sexual exploration. But recent research published by John Hopkins University researchers shows that the top parental barriers actually involve factors like vaccine safety and lack of knowledge of its necessity.³⁹

This just reinforces the need for more public health education about the importance of getting children vaccinated early. And some experts have even suggested that campaign messaging should focus on the vaccine being a cancer-prevention (rather than STD-prevention) measure to impress its importance upon parents.⁴⁰

Regular checkups help with early detection

HPV cancers may take decades to appear as the virus can lay dormant for a long time.⁴¹ This is why regular cervical screening is crucial for women to ensure early detection and treatment. The US Department of Health and Human Services recommends women between 21-65 years old get Pap tests every 3 years. It's been found that the cure rate for women whose cervical cancer is detected through a pap test is 92%, while this drops to 66% for those that are diagnosed through symptoms.⁴² ⁴³

Unfortunately, there’s currently no equivalent of a Pap smear for other penile or oropharyngeal cancer. So individuals are often left to look out for physical symptoms themselves and have to rely on astute primary care physicians to recommend further examination.

For anal cancer, a Pap test equivalent does exist for its early screening but it's not as well studied as the cervical Pap test. According to the American Cancer Society, it's still not clear how effective it is at reducing anal cancer risk and how often it should be done.⁴⁴

However, experts are suggesting high-risk individuals like men who have sex with men, and women who have had cervical cancer might benefit from anal Pap test screenings.⁴⁵ This is because when detected early, the 5-year survival rate from anal cancer is 70%. But when detected at a late stage, this percentage drops dramatically.⁴⁶

Condom use is important, but not a guaranteed strategy

Using condoms and dental dams during sexual intercourse and oral sex is can also prevent the spread of HPV — and it's crucial to use it properly. However, this strategy cannot guarantee 100% protection. This is because any area of exposed skin that's not covered by the condom can still get infected.

Some studies have estimated that condoms are about 70% effective in preventing HPV transmission. So some protection is better than none. And this is why the CDC also recommends maintaining mutually monogamous sexual relationships with partners to reduce this risk as well.⁴⁷ ⁴⁸

The tools to prevent HPV are available — we just have to use it

Researchers are continually finding better ways to screen and treat various HPV-related cancers. But the one consistent message from experts and public health bodies is that preventing HPV infection is the best way to combat it. And this is done through early vaccination — before a person becomes sexually active.

More effort needs to be made to educate the public about the nature of HPV infections and the available vaccine. The current lack of awareness is leading to too many cancer cases and deaths that could have been easily prevented.

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The author, Dawn Teh, is a health writer and former psychologist who enjoys exploring topics about the mind, body, and what helps humans thrive.