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Does HPV vaccine help if already infected?

Human papillomavirus (HPV) is a very common sexually transmitted infection that can cause health problems like genital warts and cancer. There are many different types of HPV, with some high-risk types more likely to cause cancer. HPV infections are so common that nearly all sexually active people get infected at some point.

The HPV vaccine offers safe and effective protection against HPV infection and disease. But what if you’ve already been exposed to HPV? Will the vaccine still provide any benefit? Here’s what you need to know.

HPV Vaccination Recommendations

The Centers for Disease Control and Prevention (CDC) recommends routine HPV vaccination for boys and girls ages 11-12 years old. Catch-up vaccination is recommended for females through age 26 and males through age 21 if not previously vaccinated.

Three doses are needed for full protection. The vaccines are over 90% effective at preventing infection and disease from targeted HPV types when given before exposure.

So the ideal time to get vaccinated is before becoming sexually active and getting exposed to HPV. But not everyone gets the shots at the recommended ages.

Prevalence of HPV Infection

HPV is extremely common. According to the CDC, nearly 80 million Americans are currently infected with HPV, and about 14 million new infections occur every year.

About 1 in 4 people in the U.S. are infected with a high-risk HPV type that can cause cancer. Most people clear the infection on their own, but for those who don’t, HPV can lead to:

  • Cervical cancer in women
  • Cancers of the vagina, vulva, penis, anus, and oropharynx (back of the throat, including base of the tongue and tonsils)
  • Genital warts

So there’s a good chance that many young adults eligible for the vaccine have already been exposed to HPV. Does that mean the vaccine won’t be effective?

HPV Vaccine Still Offers Protection

The HPV vaccine targets the HPV types most likely to cause cancer, including types 16 and 18. But there are over 100 strains of HPV, and the vaccines don’t protect against all of them.

So even if you’ve been exposed to some strains, the vaccines can still provide protection against other high-risk types you haven’t encountered. Clinical trials have shown the vaccines are effective at preventing disease in young women with evidence of prior HPV exposure.

According to the CDC, people who’ve already had an HPV infection can still benefit from vaccination. That’s because it’s unlikely they’ve been exposed to all types covered by the vaccines.

The vaccines may also offer some protection against HPV strains closely related to the target types. So they can provide at least partial cross-protection against non-vaccine HPV types.

Benefits of HPV Vaccination After Infection

Here are some key reasons why HPV vaccination may still help after you’ve been infected:

Prevents future infections from targeted types

Even if you’ve been exposed to certain high-risk HPV types, the vaccines can stop future infections from the types they cover. This will reduce your chances of getting HPV-related diseases in the future.

For example, if you’ve been infected with HPV type 18, the vaccine can still protect against additional exposures to type 18 infection. The vaccine could also prevent acquiring infection with other cancer-causing types like HPV 16.

May help clear existing infections

Some research shows the vaccine may help clear already established HPV infections.

A 2018 study found young women with evidence of a past HPV infection were more likely to clear the infection if they got the vaccine. So the shots may help your body get rid of the virus even if you’ve already been exposed.

Boosts other immune responses against HPV

Vaccination may supercharge virus-fighting antibodies and cells your body has already started making after exposure to HPV.

In people previously infected, the vaccine can strengthen immune memory and lead to higher antibody levels against the virus. This immune boost may improve your body’s defenses against HPV and ability to clear infection.

Reduces viral load

If unable to fully clear the infection, vaccination might lower the amount of virus in infected tissues. Having less virus means lower risk of developing HPV-related diseases.

Prevents reinfection and future disease

Getting vaccinated can prevent getting infected again with the same HPV type. Reinfection with high-risk HPV types increases the chance of developing precancerous lesions and cancer.

For example, a woman whose body clears an HPV 16 infection still remains at higher risk of getting re-infected with HPV 16, which could eventually lead to cervical cancer. But the HPV vaccine can protect against catching the same strain again.

Stopping reinfection reduces the total time HPV lingers in the body. This lowers the risk of progression to more serious HPV-related diseases, like cervical, anal, or head and neck cancers.

Is vaccination after HPV exposure as effective?

The HPV vaccine appears to be most effective when given *before* first exposure to the virus. Immune responses are strongest in people not previously infected.

Some research shows vaccination is less effective in those already infected with HPV compared to those with no history of infection. The reasons are not entirely clear but may include:

– The body may not mount as strong an immune response to the vaccine after a natural HPV infection.

– Early exposure to HPV may dampen the vaccine’s effectiveness.

– It may be harder to clear infection if HPV has already persisted in the body.

However, the vaccine can still lower the chances of future infection and disease in those previously exposed. So while vaccination after infection may be somewhat less effective, experts agree it still offers important protection.

Is the HPV vaccine safe for adults?

Yes, the HPV vaccine is very safe for adults up to age 45. Side effects are usually mild like pain, redness, or swelling at the injection site.

The vaccines have been extensively tested in clinical trials and monitored for safety since first introduced over a decade ago.

As of 2018, over 270 million doses of HPV vaccine had been distributed worldwide. Monitoring data continues to show the vaccines have excellent safety profiles.

The most common side effects from the HPV vaccine are:

Side effect Rate
Pain, redness, or swelling at injection site 8 in 10
Headache 1 in 2
Fever 1 in 10
Nausea 1 in 4
Dizziness 1 in 100

Serious side effects like severe allergic reaction are very rare, estimated around 1 case per million doses. There is no evidence the HPV vaccine causes long-term health problems.

When should adults get the HPV vaccine?

The CDC recommends routine HPV vaccination for young adults up to age 26 for women and age 21 for men. Beyond those ages, the decision to get vaccinated is an individual one.

Some medical groups also recommend vaccination for adults ages 27-45 as part of shared clinical decision-making with your healthcare provider.

Reasons adults ages 27-45 may consider getting vaccinated for HPV include:

– Women – To reduce the risk of cervical cancer and precancer

– Men – To reduce the risk of genital warts and anal cancer

– MSM (men who have sex with men) – For protection against genital warts and anal cancer

– At risk HIV-infected persons

– Anyone with a weak immune system

Keep in mind that age alone doesn’t preclude vaccination – even if you’re over age 45, you can still potentially benefit from the shots. Talk to your doctor about your individual risk factors and whether vaccination is advisable for you.

Bottom Line

The HPV vaccine is recommended primarily for adolescents before sexual activity and exposure begins. However, age alone should not preclude vaccination in adults.

Those who’ve already been infected with HPV can still gain protection from getting the vaccine. It prevents future infections and diseases caused by HPV types targeted by the vaccines.

The shots may also help the body clear an existing infection more quickly. This can lower the risk of HPV-related health problems developing down the road.

Adults may consider getting vaccinated based on their age, gender, sexual practices, and other risk factors. While the HPV vaccine may be somewhat less effective after infection, it still helps reduce the chances of getting HPV-related cancers and diseases.


HPV is extremely common – most sexually active adults get infected at some point. Although the vaccine works best when given before exposure to the virus, it still benefits adults who’ve already had an HPV infection.

Vaccination can provide protection against HPV types someone hadn’t previously encountered. It may also boost the body’s ability to clear an existing infection and defend against reinfection. This reduces overall HPV exposure that could otherwise lead to cancers and other diseases later on.

The HPV vaccine is safe for adults up to age 45 and beyond. Those at higher risk due to age, gender, or sexual practices may consider getting vaccinated against HPV even after prior infection. Shared decision-making with a healthcare provider can help adults weigh the potential benefits and risks. While not as effective as vaccination before HPV exposure, the shots can still help reduce future infection and disease risk.