HPV vaccination is a shot that protects against human papillomavirus, the most common sexually transmitted infection and the primary cause of several types of cancer. The vaccine works by training your immune system to recognize and block HPV before it can cause an infection. It currently protects against nine strains of the virus and has already reduced cervical precancers by 40% and the overall risk of developing cervical cancer by more than 80% since its introduction.
How the Vaccine Works
The HPV vaccine contains no live virus. Instead, it’s made from lab-produced proteins that mimic the outer shell of the real virus. These protein shells, called virus-like particles, look enough like HPV to trigger a strong immune response but can’t cause infection or disease. When injected, they prompt your body to produce antibodies against nine HPV types: 6, 11, 16, 18, 31, 33, 45, 52, and 58.
Two of those strains (6 and 11) cause roughly 90% of genital warts. The remaining seven are high-risk types responsible for the majority of HPV-related cancers. Once your immune system has built antibodies, it can neutralize those strains quickly if you’re ever exposed to them in real life.
Which Cancers It Prevents
Most people associate HPV vaccination with cervical cancer, but the vaccine’s reach is broader than that. It protects against the HPV types that cause most cervical, vaginal, vulvar, penile, anal, and oropharyngeal (throat) cancers. That makes it relevant for everyone, not just women. HPV-related throat cancers, for example, are now more common in men than cervical cancer is in women in the United States.
The vaccine is most effective when given before any exposure to HPV, which is why it’s recommended well before most people become sexually active. But even for those who have already been exposed to one or two strains, the vaccine still offers protection against the remaining types they haven’t encountered.
Who Should Get It and When
The CDC recommends HPV vaccination starting at age 9, with a routine recommendation at ages 11 to 12. Catch-up vaccination is available through age 45 for those who weren’t vaccinated earlier. The number of shots you need depends on when you start.
- Ages 9 through 14: A two-dose series, with the second shot given 6 to 12 months after the first. The minimum gap between doses is 5 months.
- Ages 15 through 45: A three-dose series. The second shot comes 1 to 2 months after the first, and the third follows at 6 months. Minimum intervals are 4 weeks between the first and second dose and 12 weeks between the second and third.
People with weakened immune systems also receive the three-dose series regardless of age. The younger schedule requires fewer shots because the immune response in preteens is stronger than in older teens and adults, producing equally robust protection with just two doses.
Single-Dose Programs Around the World
A growing body of evidence suggests that even a single dose of HPV vaccine provides strong, lasting protection. The World Health Organization issued recommendations in 2022 supporting single-dose schedules as an alternative approach, and as of September 2024, 57 countries have adopted single-dose programs. WHO estimates this shift allowed at least 6 million additional girls to be vaccinated in 2023 alone, pushing global coverage among girls aged 9 to 14 from 20% in 2022 to 27% in 2023. In the U.S., the standard two- or three-dose schedule remains the current recommendation.
How Long Protection Lasts
Clinical trials and post-licensure studies show that HPV vaccination provides protection lasting more than 10 years with no sign of weakening over time. No booster dose is currently recommended. Research tracking vaccinated individuals continues, but so far the data show no drop-off in effectiveness. For a vaccine given in adolescence, that means protection extends well through the years of highest HPV exposure risk.
Common Side Effects
The most frequently reported side effect is soreness, redness, or swelling in the arm where the shot was given. Some people also experience mild fever, headache, fatigue, nausea, or muscle and joint pain. These reactions are typical of many vaccines and generally resolve within a day or two.
Fainting shortly after the injection is reported more often with HPV vaccination than with some other vaccines, particularly among adolescents. This is a well-known response to needles in that age group rather than a reaction to the vaccine itself. Clinics typically ask patients to sit or lie down for 15 minutes afterward as a precaution.
Safety Track Record
More than 80 million doses of the HPV vaccine were distributed in the United States between 2006 and 2017. During that period, the national adverse event reporting system received about 36,000 reports. Of those, 93% were classified as non-serious, covering the expected side effects like injection site pain and brief dizziness. About 7% were classified as serious, a category that includes any event requiring hospitalization, regardless of whether it was ultimately linked to the vaccine.
A separate review of reports between 2014 and 2017 found an even lower serious-event rate: roughly 3% of the 7,244 reports submitted. Notably, about 22% of all HPV-related reports to the system weren’t health problems at all. They involved issues like improper storage or the vaccine being given outside its recommended use. Large-scale safety monitoring through multiple independent systems has not identified patterns of serious harm linked to the vaccine.