STI Awareness: Human Papillomavirus and the HPV Vaccine

Virus-like particles, which mimic the outer shell of HPV, are used in the HPV vaccine to induce an immune response against the virus. Image obtained from cancer.gov.

January is Cervical Cancer Awareness Month, which gives us an opportunity to learn about the virus that causes most cancers of the cervix (as well as other cancers). More than six million Americans are infected with human papillomavirus (HPV) every year, making it one of the most common sexually transmitted infections. There are more than 100 different strains of the virus, some of which can cause genital warts and others of which can lead to cancer. In most cases, an HPV infection will clear up within eight to 13 months, but it can lurk undetected for years, which makes cancer screening very important for anyone who has been sexually active.

Most sexual activities – especially those involving genital-to-genital contact, i.e., vaginal and anal intercourse or simply rubbing genitals together, but also those involving oral and manual contact – can transmit HPV. Although HPV is best known for its connection to cervical cancer in women, it can affect either sex and cause cancers of the vulva, vagina, cervix, penis, anus, oral cavity, or pharynx.

Together, HPV-16 and HPV-18 cause about 70 percent of cervical cancers. Fifty percent of U.S. women who die of cervical cancer have never had a Pap smear; in countries without widespread access to Pap smears, cervical cancer remains a major cause of death. 

A person carrying HPV can transfer the virus to a sexual partner through skin-to-skin contact, probably through microscopic tears in the skin. The virus injects its DNA into the human cell, where the host’s machinery makes copies of the virus. If the infection becomes chronic, the viral DNA and host cells’ DNA combine, which leads to the production of proteins coded by the virus. While our immune systems are usually able to regulate cell division to protect against uncontrolled growth, a protein from a high-risk strain of HPV can interfere with this process, which increases the risk for tumor growth.

The search for a vaccine began in the 1980s, when HPV was confirmed as the cause of cervical cancer. In 2006, the FDA approved Gardasil and Cervarix, both of which inoculate against HPV infection. Because HPV is so easily spread and can have potentially fatal consequences, the vaccine can play a huge role in cancer prevention alongside normal screening methods. Both vaccines protect against cancer-causing HPV-16 and HPV-18. Additionally, Gardasil protects against two wart-causing strains of HPV: HPV-6 and HPV-11.

Gardasil is produced with a yeast, Saccharomyces cerevisiae, that has been genetically modified to produce only the virus’ outer protein shell. In a normal HPV infection, the virus will commandeer a skin cell, which is directed by the viral DNA to manufacture copies of the virus. The vaccine, on the other hand, does not contain viral DNA, protecting the recipient from infection. The yeast-produced proteins self-assemble into a perfect replica of the HPV outer shell. The vaccine is composed of the virus-like particles, an adjuvant, and a buffer, all of which are suspended in a sterile liquid. The antibodies a vaccine recipient produces in response to the impostor viral proteins protect him or her from future infection by the actual virus. The body can now recognize the outer shell of HPV and stimulate an immune response to it upon subsequent exposure.

The HPV vaccine is approved for anyone between the ages of 9 and 26. Because cervical cancer is the most common cancer associated with the virus, the vaccine is generally marketed toward girls, but there are reasons to administer it to boys as well. Though not as common, HPV can lead to cancer in males. At the very least, a male can pass the virus to his sexual partner(s), putting them at risk. Additionally, Gardasil protects both males and females against the most common types of genital warts. Widespread vaccination, regardless of sex, reduces the prevalence of the virus in the general population, which benefits everyone.

In the United States, controversy has surrounded the introduction of the HPV vaccine. On one side, there are religious objections related to the sexual aspect of the disease, and on another side, there is a distrust of vaccines among a significant minority of people. In 2008, 37 percent of girls, ages 13 to 17, initiated the HPV vaccination process, and only half of this group completed it.

Many Planned Parenthood health centers, as well as other clinics and health-care providers, offer the HPV vaccine. More information about HPV and the vaccine is available on the websites for Planned Parenthood and the Centers for Disease Control.

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8 responses to “STI Awareness: Human Papillomavirus and the HPV Vaccine

  1. Anna, this was fascinating. Thanks for giving us the scientific info, without being overly “facty.”

    I am torn about the efficacy of the HPV vaccine. I think it’s a good thing to offer, but I am opposed to school districts making the vaccine mandatory, the way that some other vaccines (such as MMR) have become. I’m in the camp that is suspicious of vaccines. We don’t know the long term health effects of the vaccine yet, so we shouldn’t make it mandatory until all the evidence comes in. That’s just my opinion, though . . . I know a lot of people disagree with “conspiracy theories” about the use of vaccines.

  2. I’m glad you enjoyed reading it, Serena. It was fascinating for me to research and I’m glad that excitement can come across to other people.

    One great thing about studying biology is that it is starting to demystify science for me — for most of my life it seemed so untouchable and inaccessible. I first started researching the HPV vaccine in late 2009, for a term paper I was writing. Before I started my research I was skeptical too, but by the time I was done I was confident that I’d get the vaccine myself if it had been available when I was young enough to have it. Since then I’ve researched it further, for another class project, and the more I learn the less weird it seems.

    It is so easy to be excused from the mandatory vaccinations that there are schools with high rates of unvaccinated children, and this is even starting to lead to outbreaks, such as the recent measles outbreak in California. Although the putative connection between the MMR vaccine and autism has been debunked, a lot of people still think there is a causal relationship between the two, which probably fuels a lot of the objections to that vaccine. There is controversy surrounding other vaccines, such as DPT — and infant deaths from pertussis have been connected to exposure to individuals who have not had the DPT vaccine.

    There have definitely been problems with vaccines before, but the problems can be addressed and at the end of the day, I think the widespread protections offered by vaccines far outweigh the risks of a new vaccine. In our society, however, the diseases MMR and DPT vaccines protect us from are so rare that it seems like it’s more of a risk to be vaccinated. But a big reason they are rare is because of widespread vaccination. Vaccines have saved countless lives, and we’ve even driven the smallpox viruses to extinction (it remains in storage in a couple of laboratories) and have all but eradicated polio in the Western world, where vaccination was widespread. When we don’t have everyday exposure to things like smallpox and polio, and even measles, it’s easy to take vaccines’ potential for granted.

    I agree with you that the HPV vaccine hasn’t had time to generate good evidence about long-term effects. We don’t know how long it’s effective and when exactly you will need booster shots. I don’t know how I feel about making it mandatory at this point, but I do think that education about its benefits should be part of comprehensive sex education in our schools. Even though I had comprehensive sex education in the early-’90s, we were never told that HPV can potentially lead to cancer — and a nonscientific survey of friends in my age group revealed that this connection was not made explicit to almost any of us. I think it’s important to stress that this easily spread virus can lead to cancer, so an unvaccinated person can make the decision for himself or herself before becoming sexually active. But of course, all of this hinges on my own pipe dreams about comprehensive sex education in the schools and minors’ ability to access sexual-health services without parental involvement. Sigh!

    • Wow – thanks for the detailed response, Anna. Lots of points to consider.

      As to smallpox, this might be off topic, but I read a book called Saving the World, by Julia Alvarez. She told the story of how the smallpox vaccine was created. Orphans from Spain were intentionally infected with cowpox and then taken to Spanish colonies to help eradicate smallpox. Many of them died in the journey, but it was viewed as necessary to help the greater good. That being said, you make a good point . . . no one gets smallpox or polio anymore, thanks to vaccination programs.

      In terms of the MMR and DPT vaccines being linked to autism, can you provide a link to information about that being debunked? I don’t doubt your facts – I would just like to learn more for myself.

      Even though I’m skeptical of an HPV vaccine, I totally support the search for an HIV/AIDS vaccine. Funny how that works.

      • One thing that is really interesting to me, because I’m a dork, is the way clinical trials are designed. It was only recently — like in the past several decades — that scientists really started to put ethical guidelines into place. “Informed consent” wasn’t much of a concept as recently as the 1950s when oral contraceptives were being studied in the most large-scale clinical trials of their time. I love science and the scientific method, but I also love ethics. There have been ethical problems in the past (see Tuskegee for what is perhaps THE paragon case of unethical science), but I believe that we can enact the scientific method ethically, without sacrificing one iota of rigor.

        The alleged MMR-autism link is interesting. The furor started in 1998 when The Lancet published an article by Andrew Wakefield. They have since retracted the article and Wakefield’s coauthors have disowned the piece. But the article made such a splash in the public consciousness that 1 in 5 Americans still believes vaccines cause autism. This is an article from almost exactly a year ago, when the piece was retracted by The Lancet. Here is an article from last May, about Wakefield being stripped of his medical license in the UK. This is a recent editorial that has interesting information about the public’s suspicion toward vaccines in general, and also links to the most recent — and very thorough — debunking of Wakefield’s study published in the British Medical Journal. The belief that there is a connection between vaccinations and autism will probably not easily die, because it’s so easy to confuse correlation with causation — symptoms of autism start emerging at around the same time children are getting vaccinated.

        I don’t think DPT was ever formally connected with autism, but many members of the general public make that connection. DPT scares in previous decades had to do with an alleged link with seizures and brain injury. Continuing suspicion toward vaccines in general keeps vaccination rates lower than they would be otherwise. It looked like pertussis (whooping cough) was going to be wiped out completely (at least in countries where DPT vaccination was widespread), but recently its rates have been climbing upward. There are many reports of infants, who are too young to be vaccinated, getting pertussis from unvaccinated individuals who themselves are able to fight it off but can transmit it to more vulnerable people. NPR has an interesting story about these issues.

  3. This is a great post! It was great to read an explanation of how the vaccine actually works, and I really appreciated that you stressed the importance of anyone who is/going to be sexually active receiving it, regardless of their sex. My understanding is that HPV tests for people with penises are not as good at detecting the virus as a pap smear, which is another reason that not only those of us with cervixes should get it. I hope doctors are recommending it to patients in the right age range across the board. And I wish it’d been around when I was younger!

    • Such a good point, Nicole. I think it’s important to point out the homophobia involved in leaving boys out of the vaccination debate. It’s not just a gender equity issue. But yes . . . if there IS going to be a vaccine, it should be equally applied.