The ABCs of the HPV Vaccine

If someone told you there was a vaccine that could prevent most cases of cervical cancer—and a growing number of head and neck cancers—would you get it? Would you want your children to get it?

An increasing number of parents are opting to have their children receive this cancer-preventing vaccine, which protects against human papillomavirus (HPV), a virus associated with about 43,000 new cases of cancer each year. Still, Yale Medicine experts say work remains to be done when it comes to educating families about the importance of the vaccine.

HPV is a group of more than 150 related viruses (called types or strains), some of which can cause genital warts and cancer. It is spread through vaginal, anal, or oral sex, or through skin-to-skin contact during sexual activity with someone infected with the virus. In fact, HPV is the most common sexually transmitted infection in the United States. An estimated 79 million Americans—most in their late teens and early 20s—are infected with it, according to the Centers for Disease Control and Prevention (CDC).

Most of the time, the body clears an HPV infection within two years on its own. The infections that linger, however, can cause cellular changes that, years later, can turn into cancer. That’s why it's recommended that children—both girls and boys—be immunized before they become sexually active. (The vaccine won’t cure an existing infection or offer protection against an HPV strain if someone has already been exposed to it.)

The vaccine is often discussed in the context of preventing cervical cancer, but its benefits extend beyond that. The vaccine also protects against the types of HPV that cause most genital warts, in addition to vaginal, vulvar, and anal cancers. HPV can also lead to penile cancer in men and oropharyngeal cancer (a type of head and neck cancer) in both sexes. In fact, oropharyngeal cancer is now the most common HPV-associated cancer in the U.S., according to the CDC. (The CDC notes that while the vaccine’s ability to prevent penile and oropharyngeal cancers has not been established, it has been shown to protect against the types of HPV that often cause those cancers.)

The CDC recommends boys and girls receive two doses of the HPV vaccine (called Gardasil 9) between ages 11 and 12. The first HPV vaccine (Gardasil) was approved by the Food and Drug Administration (FDA) in 2006 and offered protection against four HPV types, including types 16 and 18, which cause 70 percent of all cases of cervical cancer and precancerous lesions. In 2014, the FDA approved Gardasil 9, which protects against those four HPV types, plus five more.

In October 2018, the FDA extended the age range for people to receive the vaccine to include 27- to 45-year-olds. Previously, the vaccine had been approved for those between the ages of 9 and 26.

So, adults should speak with their primary care physician about the vaccine for themselves, too.

The best time for administering a vaccine is typically during a child’s 11- or 12-year wellness visit, says Maryellen Flaherty-Hewitt, MD, a pediatrician and associate professor of clinical pediatrics at Yale School of Medicine.

“In our office, we often combine it with other vaccines children are receiving at that wellness visit, such as tetanus and meningitis,” Dr. Flaherty-Hewitt says. “But we are giving information to parents at the 9-year visit. We tell them that this is a cancer prevention vaccine, and it becomes a fruitful discussion, and something for them to think about.”

Two doses—delivered six to 12 months apart—are needed. “So, what’s nice is if they get it when they come in at 11, they can get the second shot when they turn 12,” she says. “It doesn’t require an extra doctor’s appointment.”

However, if a child waits until age 15 to get the immunization, three doses are required. (Originally, three doses were recommended universally, until studies focused on 9-to-14-year-olds showed two doses were just as effective. Such research has not yet been done for children over age 15.)

“Getting two shots instead of three is a big selling point for patients who are afraid of needles,” says Alla Vash-Margita, MD, chief of Pediatric and Adolescent Gynecology.

Plus, the younger a child is when they receive the vaccine, the stronger immune response they mount to it, offering better protection, explains Sangini S. Sheth, MD, MPH, an obstetrician-gynecologist and assistant professor of obstetrics, gynecology, and reproductive sciences at Yale School of Medicine.

When the HPV vaccine first came out in 2006, it was largely marketed to parents of girls because of the high association between HPV and cervical cancer. It wasn’t until 2011 that the CDC recommended it be included in the routine immunization program for boys.

This is key, because later in life, oropharyngeal cancer, which affects the tonsils, soft palate, parts of the throat, and the back of the tongue, poses a particular threat to men.

“Initially, the focus had been on getting young girls immunized because of cervical cancer, and certainly, that is still a huge reason to get this vaccine, but there are other types of cancer that will affect both men and women,” Dr. Flaherty-Hewitt says. “Plus, by vaccinating young men, too, that also helps decrease cervical cancer rates because they then can’t spread those HPV strains.”

The best way to connect with parents—and children—when discussing the HPV vaccine, Dr. Flaherty-Hewitt says, is to focus on protection from cancer.

“With every vaccine I give, if a child asks me why I am doing it, I say it’s to keep them healthy,” she says. “Likewise, when a kindergartner is looking at me with tears in her eyes because she doesn’t want to get an immunization, I tell her it’s about protecting her health. I keep it simple. I don’t explain that the tetanus shot, for example, is to prevent lockjaw.”

If parents wish to talk more with their children about the particulars of HPV, she encourages them to do so or helps to facilitate a conversation. “Depending on their child’s developmental stage, they can choose to get into what this particular virus is caused by,” Dr. Flaherty-Hewitt says. “Often, kids know more than we think, so parents may want to talk to them more directly about it.”

The HPV vaccine has been deemed both safe and effective by the CDC and FDA. The biggest side effect is discomfort at the site of the injection, says Dr. Vash-Margita, who is also an assistant professor of obstetrics, gynecology, and reproductive sciences at Yale School of Medicine.

“Kids will say they are sore, or a few might get dizzy or light-headed, which is why we watch kids for five to 10 minutes after they receive the vaccine to make sure they are OK,” she says.

In addition to pain, other common side effects are temporary and include fever, nausea, and swelling and redness at the site of the injection.

The number of adolescents receiving the HPV vaccine is slowly climbing. The CDC reports that the number of 13- to 17-year-olds who have completed the vaccine series grew an average of 5 percentage points from 2016 to 2017.

In 2017, nearly 66 percent of adolescents ages 13 to 17 received the first dose of the vaccine series, and nearly 49 percent of adolescents in the same age group had completed the series.

“The goal for adolescents is a vaccination rate of 80 percent,” Dr. Sheth says. “This target is reachable. There are other countries that have been able to reach those rates and are already seeing dramatic benefits either in their rates of warts or their rates of dysplasia (precancerous changes) in their populations.”

An important factor, Dr. Sheth says, is for every clinician to recommend the vaccine. “A clinician's recommendation means a lot to families and children and adults,” she says.

Dr. Vash-Margita agrees. “The vaccine is very safe and has been on the market for 12 years,” she says. “I tell my patients and their families, ‘This is the only vaccine the medical establishment has against any kind of cancer. Please do it.’”

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