The HPV vaccine, first approved in 2006,  is the latest addition to the CDC’s schedule of recommended childhood vaccinations. Other nations, including Canada and Australia, have approved the vaccine. In this post, we’ll review the science about HPV, recommendations from medical institutions, the controversies, and my personal plans on vaccinating my family.

What is HPV?

HPV, or human papillomavirus, is a type of virus. There are over 170 known viruses in the HPV family of viruses: some cause “benign lesions” and warts, whereas others cause cancer. The International Agency for Research on Cancer has categorized 13 different HPV viruses as known carcinogens: this means that there’s sufficient evidence to establish that these 13 HPV viruses cause cancer (for more information on the IARC, please see this post). These viruses are known as “high-risk HPVs” (post continues after infographic). 

How does HPV cause cancer?

The virus infects the cells that line our organs, otherwise known as the epithelium. According to the National Cancer Institute (NCI), once the virus infects our cells, it starts making two proteins which interfere with our own cells’ ability to control their growth. In the vast majority of cases, HPV infections are harmless as our immune system usually takes care of these infected cells. But sometimes, the growth of cells continues unchecked leading to more mutations and eventually leading to cancer. We do not know why high-risk HPVs develop cancer in some cases, while in most cases it does not. We do know that some activities, such as smoking among others, increase the likelihood of developing cancer from an HPV infection.

The NCI states that it can take 10-30 years from the infection till the development of cancer and during this time there are no symptoms. This makes it hard to determine how the virus was transmitted.

How many cases of cancer are caused by HPV?

HPV has been associated with various forms of cancer including cancer of the cervix, vagina, vulva, penis, anus, rectum, and oropharynx (throat). According to a study cited by the CDC, an average of 79% of these cancers are probably caused by HPV, but can be as high as 91% of cases. This represents an average of 31500 cancer cases per year in the United States.

Additionally, the CDC estimates that HPV caused approximately 350,000 cases of genital warts per year prior to the development of the HPV vaccine (see sections below on the vaccine).

How is HPV transmitted?

HPV is the most common sexually transmitted disease. According to Planned Parenthood, sexual skin-to-skin contact is all that is required for the transmission of the virus, meaning that a condom will not prevent the transmission of the virus (but it does reduce its transmission). As such, cases of HPV have been observed in both males and females who have not experienced sexual intercourse (i.e. virgins). There is also some evidence that HPV can be transmitted from mother-to-child at the time of birth. You cannot get HPV without skin contact, meaning you can’t get it from a hard surface such as a doorknob or toilet seat. 

The only way to not get HPV is to not have sexual contact with another person. To reduce the chances of getting HPV, Planned Parenthood recommends getting vaccinated, and using condoms and/or dental dams. To reiterate, these methods will not prevent the transmission of HPV.

Is there a test for HPV?

There are diagnostic tests for HPV, but these have only been approved to test the cells that are obtained from a Pap smear. So there’s no blood test for HPV, in the same way that there is for HIV. A Pap smear will also help detect cells that have started growing unchecked in the cervix. Consequently, it is important to have regular checkups with the doctor and to prevent the transmission of HPV.

What is the HPV vaccine?

The HPV vaccine protects against infection from some types of HPV. If you are already infected with HPV, it will not make these go away. If you are already infected with HPV, the vaccine can protect against infection from other types of HPV you do not already have.

There are 3 vaccines on the market: Cervarix, Gardasil, and Gardasil 9. All of them protect against infection from HPVs 16 and 18, which account for 70% of cervical cancers. Gardasil additionally protects against HPV 6 and 11, which account for 90% of genital warts. Gardasil 9 protects against 5 additional types of HPV that have been associated with cancer. Due to this increased protection, only Gardasil 9 is currently available in the United States. The other vaccines are available in other countries. In Canada, as of 2017, Gardasil 9 will be offered in schools in Ontario.

According to the World Health Organization, in 2017, 71 nations had introduced the HPV vaccine for girls, and 11 countries had also introduced it for boys as part of their national immunization programs. This discrepancy may be because cervical cancer accounts for 84% of all HPV-related cancers, so the importance of immunizing girls may be considered to be more urgent. However, the HPV vaccine has been approved to prevent genital warts as well as anal cancer in boys/men.

How do the HPV vaccines work?

The vaccines have particles that resemble the virus, so they rely on our body’s immune system to develop antibodies against these particles. The vaccines do not have viral DNA in them and lack other key pieces of the virus, so you cannot get HPV from the vaccine.

Who should get vaccinated?

Talk to your doctor to find out if you qualify for the vaccine. In general, the CDC recommends that the following individuals get vaccinated against HPV:

• All girls and boys who are 11 or 12 (note that vaccinations can start at 9 years of age).
• Women or teens through the age of 26 who have not been vaccinated. In 2018, the FDA approved the vaccine to include individuals through the age of 45. 
• Men or teens through the age of 21 who have not been vaccinated.
• Men through the age of 26 who have sex with men.
• Transgender individuals through the age of 26.
• Individuals who are immunocompromised (including HIV) through the age of 26.

It is important that the HPV vaccine be given before individuals are exposed to HPV. It is important not to wait until you are sexually active to receive the vaccine.

The vaccine is not a replacement for a Pap test.

How many vaccinations are there?

The number of vaccinations your child needs depends on when they start getting vaccinated. According to the CDC, if vaccinations start before the age of 15, then only 2 shots are needed. These two shots should be spread out by 6-12 months. If vaccinations started after the age of 15, then 3 doses are needed, where the second dose is given 1-2 months after the first, and the third dose is given 6 months after the first.

The difference is doses is because studies have shown that 2-doses, where the first dose is given before the age of 15, are “as good or better” than 3-doses after the age of 15. It is equally important that the doses in the 2-dose schedule be spread out by 6-12 months.

How effective is the vaccine at reducing the risk of cancer?

The National Cancer Institute highlights that the initial trials for the HPV vaccines found that they are nearly 100% effective at protecting against infection from the viruses against which they’re designed. It is important to note that protection against all HPVs associated with cancer is not yet available, but developing a vaccine that targets all high-risk HPVs is of importance since the prevalence of the HPV viruses varies in different populations. Due to the difference in the prevalence of each high-risk virus in different populations, some studies suggest that the current vaccine may not offer as comprehensive a protection to minorities and underserved populations than to European Americans.

The World Health Organization points out that nations that have incorporated the HPV vaccine into their immunization programs have seen “50% decrease in the incidence rate of uterine cervix precancerous lesions among younger women.” Studies estimate that vaccination could prevent up to 90% of cases of cervical cancer.

The CDC highlights that the Gardasil vaccine still works 10 years after the initial doses and 6 years after the initial doses of Gardasil 9, but they have to continue monitoring to determine how long protection remains.

What are the side-effects of the HPV vaccine?

According to Gardasil 9’s product insert, seven clinical trials for the vaccine were conducted which involved over 15 thousand individuals who received at least one dose of the vaccine. Redness and swelling at the site of injection increased with each dose of the vaccine.

The product insert outlines that individuals who are sensitive to yeast should not get vaccinated, nor should individuals who had a reaction to an earlier dose of the vaccine. It also reports that fainting can occur, which can be accompanied by temporary seizure-like movements. Because of this, it is recommended that the vaccinated person lie down for about 15 minutes and be monitored after the injection.

What safety studies have been conducted?

As previously mentioned, Gardasil 9 went through multiple clinical trials. At the same time, there is growing data outside of the clinical trials on the safety and efficacy of the HPV vaccines. Note that many of these studies were not conducted with Gardasil 9, since this vaccine was approved later. Here are a few studies and their results:

• A study on serious adverse effects from Gardasil, examining nearly a million girls from Denmark and Sweden. Nearly 300,000 of the individuals in the study had received Gardasil. The study concludes that they found a few associations that were very weak, and no association between the vaccine and “autoimmune, neurological, and venous thromboembolic adverse events”.

• A review conducted in the EU examining reports that HPV vaccines are associated with complex regional pain syndrome (CRPS) and postural orthostatic tachycardia syndrome (POTS). They examined data from the all three HPV vaccines and found no causal link.

• An analysis of the risk of Guillain-Barré syndrome after the HPV vaccine conducted in England. This study was important because a swine flu vaccine had previously been associated with GBS, and there were claims that the same was true for the HPV vaccine. The study looked at approximately 10 million doses of the vaccine and the risk of developing GBS soon after. The authors found no risk and highlighted that if there is a small risk that was undetected by their study, it would be less than 1.1 per million doses.
• A study examined the risk of negative pregnancy outcomes in all women in Denmark between individuals who received Gardasil and individuals who were not vaccinated. The study examined spontaneous abortions, stillbirths, birth defects, low birth weight, and other factors, and found no difference.

The World Health Organization had also reviewed data on the HPV vaccine and recommends its use. For a larger list of papers, please see SkepticalRaptor’s blog.

Why are there controversies surrounding the HPV vaccine?

As with many of the “newer” vaccines, there has been push back against Gardasil. The HPV vaccines have been released in relative quick succession, which is understandably unnerving for parents who would love to see 50 years of data on a single vaccine. As such, the independent data that we are gathering now is from individuals vaccinated with Gardasil. Individuals who oppose vaccines will often point out that there is limited data on Gardasil 9, and suggest that this is indicative of the absence of safety. 

Here’s a brief list of some additional controversies/rumors that surround the vaccine, which you may have read about:

• Japan has been faced with a lot of controversies surrounding the HPV vaccine, where the government stopped recommending the vaccine. As outlined in this article in Vox, it started due to a study allegedly demonstrating that the vaccine caused brain damage in mice, and was fueled by videos which showed girls having seizures shortly after vaccinations. An investigative report found that the mouse study had been done fraudulently, where “the mice vaccinated in the experiment had been genetically modified and produced an auto-antibody naturally during aging. Serum full of the antibody was taken from these mice, sprayed on brain sections of normal mice and photographed to show “brain damage” supposedly caused by HPV vaccine.”
• There have been claims that Gardasil causes death: a study was conducted which examined deaths that occurred soon after receiving the Gardasil vaccine, and found that the risk of death does not increase after receiving the vaccine.
• Among recent controversies is that a meta analysis conducted by a highly reputable organization has been criticized for having been done improperly, which has fanned the flames of doubt surrounding the efficacy of the vaccine.
• As with many topics, there have been single studies that have suggested harm, including a lowered probability of pregnancy, but these have consistently failed to be reproduced. There are also notions that border on conspiracy theories regarding Gardasil but have gone viral. Snopes has several articles that have examined these claims.

Does getting vaccinated against HPV increase sexual activity?

The concern that I have heard the most is that vaccinating against HPV may give our children the idea that they have a green light to be sexually active, or may increase the number of sexual partners an individual has. This is an understandable concern, and studies have examined this question. One study examined nearly 1400 girls split between who received the vaccine at age 11-12 and girls who were not vaccinated. The authors examined “sexual-activity related outcomes” measured by “sexually transmitted infections or pregnancy testing or diagnosis, or counseling on contraceptives”. They found no difference between the two groups.  A second study examined ~21000 vaccinated and ~186000 unvaccinated girls to determine if there was a difference in sexual activity. This was done by measuring the number of sexually transmitted infections. They found no difference between the two groups.

Would I vaccinate my child?

In talking with the SciMoms, we feel that there’s a lot of push back against this vaccine because we don’t like to think of our children as sexually active. But I think that this isn’t the right viewpoint to have: if someone gave you a vaccine that would prevent many different forms of cancer and the risk of side-effects was very, very low, would you take it? I’ll bet you would. Then why would you refuse to offer it to your child? I find it a bit ironic that we complain that pharma doesn’t do anything to prevent/cure cancer, yet we have a vaccine that prevents multiple forms of cancer and we aren’t seizing the opportunity to vaccinate our kids.

We all hope that our children grow up to be respectful of their partners and to have partners who are respectful of them. Whether we hope that our children wait for marriage before having a sexual relationship or whether we hope that our children explore sexual intimacy more freely depends on our cultural backgrounds, our religious beliefs, and other factors. However, in discussing this with the other SciMoms, we consider that it is most important that our children choose partners who are respectful and kind, and these qualities do not rely on virginity. As such, our children may end up in committed, monogamous relationships where HPV is a factor. Consequently, we all feel that it is our responsibility now to protect our children from viruses that can have devastating consequences later.

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This post was first written in August, 2018. It was updated in May, 2019 to include the vaccine’s extended approval.