HPV Vaccines: Separating Fiction from Fact

Gardasil is one of two HPV vaccines. It protects against two cancer-causing strains of HPV and two wart-causing strains.

You’ve probably heard a lot about the HPV vaccine, which protects against the sexually transmitted pathogen human papillomavirus — which itself can lead to cancers of the cervix, anus, throat, and more. Unfortunately, there is a lot of misinformation about the vaccine, such as Michele Bachmann’s debunked claim that it causes mental retardation. But, even before Bachmann gave us her two cents, there have been plenty of falsehoods flying around about the HPV vaccine.

Myth: Vaccination against HPV will increase sexual promiscuity among vaccine recipients.

Fact: Studies show that this fear is unfounded.

A study published this month in the American Journal of Preventive Medicine contradicts this claim. In a group of more than 4,000 young females, there was no significant difference between the vaccinated and the unvaccinated in terms of number of sexual partners or the age at which sexual activity began.

Together, HPV-16 and HPV-18 cause about 70 percent of cervical cancers.

Besides, the vast majority of teenagers who choose abstinence do so for reasons other than a fear of contracting HPV. Additionally, HPV is one of many sexually transmitted diseases (STDs); if fear of contracting an STD were the only factor in teenagers’ celibacy, a vaccine that protected against only one STD would not remove this fear.

(It might bear pointing out that when the HPV vaccine was approved for boys and men, fears about male promiscuity didn’t seem to run as rampant.)

Myth: Because the HPV vaccine only protects against two cancer-causing strains of HPV, it isn’t useful in cancer prevention.

Fact: The two cancer-causing strains of HPV that the vaccine protects against account for 70 percent of all cases of cervical cancer. Furthermore, Gardasil protects against two additional strains of HPV, which together are responsible for 90 percent of genital warts.

There are around 150 strains of HPV, about 15 of which can cause cancer. Together, HPV-16 and HPV-18 cause about 70 percent of cervical cancers. (Additionally, HPV-16 causes the vast majority of anal cancer.) It is true that the vaccine isn’t targeted against less-common strains of HPV, which is why it doesn’t substitute for regular Pap tests. It does, however, provide protection against the most common causes of cervical cancer — and along with that, reduces the frequency of abnormal Pap results that necessitate more invasive procedures.

Interestingly, there is a growing body of evidence that Gardasil offers a small degree of cross-protection against non-target HPV strains, which together are responsible for 20 percent of cervical cancers. While Gardasil’s apparent efficacy against these less-common strains isn’t nearly as strong as its demonstrated efficacy against HPV-16 and HPV-18, it does add some benefit.

Some people think the less-common HPV strains will just replace HPV-16 and HPV-18, but a recent study of 2,702 males found that an infection with HPV-16 or HPV-18 did not affect the likelihood of infection with another cancer-causing type. Other studies on females have shown the same results.

According to researchers at the University of Hawaii, so far there is no good information about whether some strains of HPV are transmitted more easily than others, but their small study seemed to suggest that HPV-16 was easier to transmit into the cervix than other strains.

One hopes that more research will determine if the HPV strains targeted by the vaccine are transmitted more efficiently than other types. Thus far, however, it appears that preventing infection with HPV-16 or HPV-18 will not open up a niche for other cancer-causing HPV strains.

Myth: The HPV vaccine has caused death in some of its recipients.

Fact: While some people have died after receiving the vaccine, their deaths were not caused by it.

Tens of millions of doses of Gardasil have been administered, and at last count, there were 71 deaths reported among Gardasil recipients. Thirty-four of these reported deaths have been confirmed by investigators, and these deaths were not found to have been caused by the vaccine. In any given population, especially in a large population, there will be some deaths. Correlation, however, does not equal causation.

The same goes for injuries reported to be correlated with any given vaccine. When a vaccine recipient has a problem following vaccination, these problems are usually found by investigators to be coincidental. The HPV vaccine has been found to be safe, with very few side effects. There is “strong,” but not “convincing,” evidence that some people might experience an allergic reaction to the vaccine.

The Vaccine Adverse Event Reporting System (VAERS) database collects claims of adverse events from anyone — health-care providers, patients, or family members. According to their website, “for any reported event, no cause-and-effect relationship has been established. Reports of all possible associations between vaccines and adverse events (possible side effects) are filed in VAERS. Therefore, VAERS collects data on any adverse event following vaccination, be it coincidental or truly caused by a vaccine. The report of an adverse event to VAERS is not documentation that a vaccine caused the event.”

[For more information on Gardasil and death, read our November 2013 piece on the topic!]

From the outside, the synthetic virus-like particles in Gardasil are indistinguishable from HPV. On the inside, however, the synthetic particles are empty while the viruses contain DNA. Image: University of Arizona

Myth: There is human papillomavirus DNA in Gardasil.

Fact: Gardasil consists of empty protein shells. The infectious portions of HPV’s genetic code are not involved in its manufacture.

HPV is composed of two main components: a protein shell and a double-stranded DNA molecule. Both HPV vaccines contain synthetic versions of the protein shell, which is sufficient to induce an immune response. These protein shells were not obtained from actual viruses but rather were manufactured in a laboratory; they do not include infectious DNA. In the manufacture of Gardasil, the shells are synthesized by yeast that has been genetically modified to express only the HPV gene that codes for the protein shells.

In short, the yeast used to produce the virus-like particles does not contain the genetic material necessary to produce the virus’ DNA molecule. It only has the HPV gene that produces the virus’ protein shell. Claims that the vaccine contains infectious particles are false.

Myth: The HPV vaccine is only approved for ages 9 to 26, but cervical cancer rarely affects this age group. Therefore, the vaccine will have no impact on cervical-cancer rates.

Fact: Cervical cancer usually appears later in life because the cancer takes a long time to develop.

The HPV vaccine is most effective if it is administered before the recipient becomes sexually active. It is true that cervical cancer mostly affects people older than 26, but this is because a chronic HPV infection, acquired earlier in life, usually takes decades to develop into cancer. Fifty to 75 percent of HPV infections occur between the ages of 15 and 25, while cervical cancer is most common among 35- to 50-year-olds.

Because the vaccine is so new, we aren’t quite sure yet how long the vaccine is effective — but according to the National Cancer Institute, the vaccines have been shown to protect against persistent HPV-16 and HPV-18 infections for up to five to eight years. As time goes on and more data are collected, we should have a better understanding of how long the vaccine provides protection and whether or not booster shots will be needed.

Myth: Cervical cancer is a relatively rare cancer whose rates have been declining for decades. Therefore, the vaccine is unnecessary.

Fact: Cervical cancer rates have been declining among women with access to Pap tests, but cervical cancer remains a leading cause of death in other parts of the world.

In countries with widespread access to health care, cervical cancer is on the decline due to the availability of Pap tests, a procedure that can detect abnormal cell growth in the cervix. If abnormal cell growth is detected before it spreads beyond the surface epithelium of the cervix and into the underlying connective tissues, it can be treated before it turns into invasive cancer. At this stage, it is almost always curable. In the United States, half of cervical-cancer deaths occur among women who have never had a Pap test; in countries without widespread access to Pap tests, cervical cancer remains a major cause of death. According to the World Health Organization, it’s the second most common cancer among the female population worldwide.

Even when chronic HPV infection is detected while still in a precancerous stage, it necessitates invasive medical procedures such as colposcopy and cryotherapy. Vaccination against HPV decreases the occurrence of precancerous lesions, which is a benefit in and of itself!

Planned Parenthood health centers, as well as other clinics and health-care providers, offer both Pap tests and the HPV vaccine. More information about the vaccine is available from Planned Parenthood and the National Cancer Institute.