Safe HPV Vaccine is Vital in Protecting Our Kids and in Preventing Cancer
Dr. Pia Fenimore
Dr. Joan Thode
This week, we examine the threat of human papilloma virus — or HPV — to our bodies and the rationale for protecting our kids and ourselves from its potential to cause cancer.
The HPV vaccine is yet another vaccine that the U.S. Department of Health and Human Services recently moved from the standard list of childhood immunizations into a category open for discussion. We want to ensure you have the facts to make these decisions for your children and teens.
HPV is a family of more than 200 related viruses, most of which are benign. However, there are some high-risk virus strains within this extended family that tend to cause cancer. Specifically, five HPV strains cause cervical, oral and throat cancers, as well as cancers of the anus, penis, vagina and vulva. Some of the “low-risk” HPV strains cause the formation of genital and oral warts.
To understand how HPV infects our cells and creates warts and cancer risk, it helps to start with an anatomy lesson about our epithelium. While we often think of epithelium as our skin, this cell classification also includes the lining of all body openings that connect with the outside world, including the mouth, throat, nose, ears, vagina, urethra and anus. To protect the intricate balance within our body, we must have a barrier wall between the outside world and that inner environment, so the epithelium is structured like the walls of a medieval fortress with several layers of cells.
Our outer layer constantly interacts with friction, pressure and minor trauma from myriad sources such as clothing, handshakes, eating, intercourse, defecation and exercise. This regularly causes the cells to rub off, making it necessary for the body to constantly make more cells to replace them. This process of constant epithelial cell replication is key to our crash course on HPV infection.
A deep basal skin cell replicates itself frequently to ensure our epithelial barrier has adequate cell layers. HPV targets and enters these basal cells, and with every cell division that follows that infection, HPV DNA will be replicated right along each new epithelial cell.
How HPV causes cancer
“High-risk” HPV strains get this classification for a few unique reasons. These strains integrate their DNA into the DNA of the epithelial cell, making the cell DNA less stable and more prone to breaking and needing repair.
DNA that’s frequently broken is at risk for the disruption of growth genes that can lead to cancer. To add additional risk, proteins created by the HPV DNA impede DNA repair molecules, leading to persistent DNA damage.
The DNA of high-risk HPV strains contains a few unique genes — called oncogenes — that affect cell growth.
One high-risk HPV oncogene allows for faster cell replication than typical; another undermines the “arrest” proteins that are part of a tumor suppression pathway that normally triggers cell death when growth is out of control. The result is more high-risk HPV cells and the loss of the system that helps to prevent cells from dividing unchecked and creating cancerous tumors. With this system broken, the uninhibited cellular growth in these affected cells leads to cancer.
High-risk HPV can inhabit cells with minimal activity for years, sometimes up to three decades, before progressing to cancer. This delay can lead to a false sense of security and the potential to spread HPV to others without any overt indications of your smoldering HPV infection.
Let’s not forget about warts
There are a couple of low-risk HPV strains that lack the oncogenes that lead to cancer, but unfortunately will integrate into the cellular DNA and cause cellular immortality and persistent cell replication. In these cases, the epithelial cells divide and divide, packing a lot of cells into a small space and creating a thickened lump of virus-filled cells that we identify as warts. Rubbing these warts or attempting to remove them leads to the rupture of cells, the spilling out of the viral copies and additional warts.
Immunization timing is critical
Thankfully, only a few strains of HPV are high-risk for cancer, and only a couple cause genital and oral warts.
The good news: All of these strains of concern are targeted by the HPV vaccine, giving the receiver immunity to all of them.
The bad news: Once the HPV virus is inside of your cells, the HPV vaccination is not effective at eradicating it. That is why HPV vaccination is suggested between the ages of 9 and 12 years. We want to train the immune cells of the body to recognize and remove the HPV virus before it can enter the cells in the first place. Equipping a preteen with immune cells targeting high-risk and wart-causing HPV strains prevents warts and cancer not just in their teenage years, but throughout their adult lives.
How does HPV infection spread?
HPV is spread through skin-to-skin contact between the genitals or mouth. The virus is highly contagious and does not require an exchange of body fluids — it simply requires contact.
Condoms do not provide adequate protection from HPV. Since most people do not know they are infected, and since infection can be silent or latent for years, it is often spread unknowingly.
Recommendations for vaccination?
The American Academy of Pediatrics recommends that children receive HPV vaccination, in a two-dose series, starting at age 9 through 12 years. The second dose should be given six to 12 months after the first dose.
If vaccination is started after age 15, then a three-dose series is recommended to ensure adequate immune response occurs.
Vaccination is currently approved up to age 26 years but is sometimes given to older individuals at risk.
What if my child is not sexually active?
More and more young people are choosing abstinence, preferring to delay sexual activity. However, the average age for loss of virginity in the United States is 17.
In addition, many teens choose to participate in intimate contact other than intercourse at a younger age and that carries HPV risk.
Moreover, even if you are certain your child is not sexually active, you cannot predict your child’s future partner’s HPV status. Even if you only ever have one partner during your lifetime, HPV transmission can occur if that one partner is infected. Since the virus can be spread silently for years, even decades, after infection, the best way to prevent HPV infection and risk is to vaccinate ahead of the exposure.
Importantly, there is no evidence that HPV vaccination encourages sexual activity.
Why do we vaccinate starting at age 9?
We start vaccination early for two reasons. The first is that research has proven that younger immune systems work better and respond more effectively to the vaccine. For this reason, if a teen receives one HPV vaccine dose before age 15, the teen only needs two doses of the vaccine.
If the teen gets a first dose after the age of 15, then three doses are needed.
The second reason: No one can predict exactly when first intimate contact will occur. Giving the vaccine early ensures that people are protected before they are exposed.
This protection then lasts a lifetime.
Is there treatment for HPV?
Currently, there is no treatment for HPV infection. Women get screened via pap smears. If there are cancer or precancerous cells, those can be treated with various methods, including cold laser ablation and surgical removal. Oral cancers are typically treated with surgery and/or radiation.
HPV vaccine side effects?
Currently Gardasil 9 is the vaccine that is most widely used. Side effects are typically very mild and include pain and redness at the injection site and less commonly fever, nausea and fatigue.
Because there is a correlation in adolescents between vaccines and fainting, your health care provider will have the patient wait 15 minutes after the injection before leaving the office.
Since 2006, more than 100 million doses of Gardasil have been given and the vaccine has been shown to be very safe.
Researchers have investigated potential links to Guillain-Barré syndrome and chronic fatigue syndrome and found no causal association with the HPV vaccine.
Additionally, there is no association between HPV vaccination and infertility. In fact, it is quite the opposite. HPV causes cervical cancer, and treatments for cervical cancer can interfere with the ability to become pregnant and can cause miscarriage.
Does the vaccine work?
Yes, the vaccine has a near-100% efficacy in preventing infection from nine types of HPV.
A study published last year showed an 80% drop in pre-cervical cancer diagnosis in young women since HPV vaccination was recommended.
And an American Cancer Society study released Feb. 23 shows that cervical cancer incidence rates in women ages 20 to 31 declined by 27% in the United States between 2016-2021, with vaccination, compared to 2000-2005, before the vaccine was available. “Across states, higher vaccination rates were correlated with greater reduction in cervical cancer incidence rates,” the study found.
The National Cancer Institute has published studies showing a dramatic decline in HPV oral infection, which is expected to produce a drop in oral cancers in the future.
Why are vaccination rates so low?
In 2023, according to the National Cancer Institute, 57.3% of adolescents ages 13 to 15 had received the HPV vaccine as recommended.
HPV vaccination rates have been relatively stagnant in recent years.
Studies show that parents cite several reasons for refusing the vaccine, including fertility concerns and concern that it will encourage sexual activity. Parents are strongly encouraged to talk to their pediatric provider about any concerns they have.
New federal recommendation
The U.S. Department of Health and Human Services now recommends HPV vaccination at ages 11 to 12, consistent with previous recommendations.
However, federal health guidance only recommends one vaccine whereas the American Academy of Pediatrics recommends two and sometimes three.
The federal change was based on studies out of Costa Rica and Kenya that indicated that one vaccine may be enough to produce immunity. Experts note that the studies behind the single‑dose approach were not properly vetted and had important limitations: The sample size of tested patients was small; there was limited follow-up; males were excluded; and the studied populations lacked diversity.
Given the safety data for the HPV vaccine and the danger of cancer, immunologists continue to recommend maintaining the two‑ or three‑dose schedule until more definitive evidence confirms the immunity conferred by a single dose.
We are all hopeful that one vaccine will be enough, but for now pediatricians strongly endorse getting the booster vaccines to ensure effective immunity.
Pia Fenimore, M.D., is a pediatrician at Lancaster Pediatric Associates and vice chair of pediatrics at Penn Medicine Lancaster General Health. Dr. Joan Thode, M.D., is a pediatrician at Penn Medicine Lancaster General Health Roseville Pediatrics. Both are fellows of the American Academy of Pediatrics.
