HPV vaccine: Who needs it, how it works

Who needs the HPV vaccine? How many doses? What about side effects? Get answers to these questions and more.

By Mayo Clinic Staff
Photo of Bobbie Gostout, M.D.

Bobbie Gostout, M.D.

Most cervical cancers are associated with human papillomavirus (HPV), a sexually transmitted infection. Widespread immunization with the HPV vaccine could reduce the impact of cervical cancer worldwide. Here's what you need to know about the HPV vaccine.

What does the HPV vaccine do?

Various strains of HPV spread through sexual contact and are associated with most cases of cervical cancer. Three HPV vaccines have Food and Drug Administration (FDA) approval in the U.S. — Cervarix is for girls only, while Gardasil and Gardasil 9 can be used for both girls and boys. Gardasil 9 offers girls protection against more strains of HPV that can cause cervical cancer.

All three vaccines can prevent most cases of cervical cancer if given before a girl or woman is exposed to the virus. In addition, all three vaccines can prevent vaginal and vulvar cancer in women, and Gardasil and Gardasil 9 can prevent genital warts and anal cancer in women and men.

In theory, vaccinating boys against the types of HPV associated with cervical cancer might also help protect girls from the virus by possibly decreasing transmission. Certain types of HPV have also been linked to cancers in the mouth and throat, so the HPV vaccine likely offers some protection against these cancers, too.

Who is the HPV vaccine for and when should it be given?

The HPV vaccine is recommended for girls and boys ages 11 or 12, although it can be given as early as age 9. It's ideal for girls and boys to receive the vaccine before they have sexual contact and are exposed to HPV. Research has shown that receiving the vaccine at a young age isn't linked to an earlier start of sexual activity.

If the three-dose series of vaccines isn't completed by ages 11 to 12, the Centers for Disease Control and Prevention (CDC) recommends that girls and women ages 13 to 26, and boys and men ages 13 to 21 receive the vaccine. However, men can still receive the HPV vaccine through age 26 if desired.

Once someone is infected with HPV, the vaccine might not be as effective or might not work at all. Also, response to the vaccine is better at younger ages than it is at older ages.

All three vaccines are given as a series of three injections over a six-month period. The second dose is given one to two months after the first dose, and the third dose is given six months after the first dose.

If there's a delay in getting the second or third vaccine, the whole series doesn't need to be restarted. But, for lasting and full protection, all three doses are recommended.

Who should not get the HPV vaccine?

The HPV vaccine isn't recommended for pregnant women or people who are moderately or severely ill. Tell your doctor if you have any severe allergies, including an allergy to yeast or latex. Also, if you've had a life-threatening allergic reaction to any component of the vaccine or to a previous dose of the vaccine, you shouldn't get the vaccine.

Does the HPV vaccine offer benefits if you're already sexually active?

Yes. Even if you already have one strain of HPV, you could still benefit from the vaccine because it can protect you from other strains that you don't yet have. However, none of the vaccines can treat an existing HPV infection. The vaccines protect you only from specific strains of HPV you haven't been exposed to already.

July 27, 2016 See more In-depth