A photograph of a woman speaking with her doctor.

Since the widespread adoption of the Pap test (also called a Pap smear) during the 1960s, cervical cancer deaths in the U.S. have plummeted by about 70 percent, according to the American Cancer Society.

And in the 1980s and '90s, research revealed that human papillomavirus (HPV) caused most cervical cancers. Scientists eventually developed a simple way to test for it, as well as a vaccine to prevent it.

These advancements have allowed doctors to prevent cervical cancer and detect it early, says Mark Schiffman, M.D., M.P.H., a senior investigator with the National Cancer Institute. “Of all the cancers,” he says, “this one, we know what we’re doing.”

But many women may still have questions about the best way to get screened, how often to get screened, and when to start screening or get vaccinated. Others might lack easy access to a Pap test or an HPV test, or they might be confused by recent changes to screening guidelines, which continue to evolve.

Last year, for example, the U.S. Preventive Services Task Force, an independent expert panel that makes recommendations to the government and medical organizations about preventive care, updated its recommendations for cervical cancer screening to include more options for screening strategies for women between the ages of 30 and 65.

more on screening tests

The goal of cervical cancer screening is to catch potentially dangerous abnormalities early, before they become cancer or progress to a serious disease—it can take precancerous lesions on the cervix years to develop into a full-blown cancer. For the most part, women who get cervical cancer in the U.S. now either haven’t ever been screened, haven’t had a screening in the previous five years, or had an abnormal result on a screening test that was never followed up on, says Joy Melnikow, M.D., M.P.H., director of the Center for Healthcare and Policy Research and a professor in the Department of Family and Community Medicine at the University of California, Davis.

Here, more on the many benefits of cervical cancer screening, plus what you need to know about the different options for prevention and screening at different ages.

HPV/Cervical Cancer Prevention Before 21

Health experts recommend against getting screened for cervical cancer if you’re younger than 21. That may seem counterintuitive, given that HPV is the most common sexually transmitted infection in the U.S., with most people first exposed to the virus in their teens and 20s.

But it’s precisely because HPV is so common in young people that screening isn’t a useful tool for very young people. Most HPV infections go away on their own and never cause harm, and cervical cancer is very rare in women under 21.

But modern medicine offers another powerful tool for cervical cancer prevention in people too young to be screened: the HPV vaccine. The Centers for Disease Control and Prevention says all boys and girls should receive two doses of the HPV vaccine at age 11 or 12—ideally before they become sexually active. (Catch-up immunizations are recommended for women up to age 26 and men up to age 21 if they missed their shots as preteens.)

The HPV vaccine is almost 100 percent effective at preventing genital warts and cervical precancerous lesions caused by the types of HPV included in the vaccine. (The current version of the vaccine, Gardasil 9, protects against nine types of HPV, including the ones most likely to lead to cancer.)

Cervical Cancer Screening in Your 20s

The USPSTF and the American Cancer Society recommend that most women (unless they have HIV or another condition that causes a compromised immune system) begin regular screening for cervical cancer at age 21, with a Pap test every three years.

After a Pap test, also called cervical cytology, the sample of tissue from your cervix is examined under a microscope for abnormal cells that could indicate cancer or could eventually become cancer. “Pap smears are looking for the effect of the virus on the cells, but in a way that’s approximate,” Schiffman says. This makes the Pap test less accurate than an HPV test (which looks for evidence of the virus itself), he says.

Yet experts still recommend a Pap test over an HPV test for twentysomethings. That’s because in your 20s, HPV is still very common, and your immune system will take care of most infections without any help. Detecting HPV at this age would likely lead to unnecessary follow-up tests and treatment for HPV infections that would never go on to cause cancer.

A Pap test is, however, more likely to miss a worrisome cell change than an HPV test is to miss traces of the virus. That’s why experts recommend people get a Pap test every three years, instead of every five years—on the off chance your Pap test missed something, it’s better to have a follow-up on your calendar for just three years later.

Cervical Cancer Screening for Those 30+

At age 30, two additional cervical cancer screening options open up.

You can choose to stick with a Pap test every three years. Another option is an HPV test every five years. The third option is doing both tests at the same time (called co-testing), also every five years.

All are similar experiences for the patient—a doctor will collect cervical cells quickly and generally painlessly—it’s only what they look for in the lab that’s different (a virus in the case of an HPV test; irregular cells that could indicate cancer in the case of the Pap; both in the case of co-testing).

Experts say you can wait five years between HPV tests because of the test’s heightened accuracy compared to a Pap. A negative result on an HPV test is “more reassuring” than a negative Pap, Schiffman says—with a negative result on an HPV test, you can be more confident that there’s truly nothing wrong.

Also, by the time you’re 30, HPV infections are less likely to resolve on their own and may be more likely to develop into cancer. That’s why the HPV test can be a reasonable choice after age 29 (though it’s important to note that a positive HPV test does not mean that you have cancer or are destined to get cancer).

Co-testing is also an option—and in the U.S. right now, in many places, co-testing may be the only available screening strategy for people who want to space their testing out every five years instead of every three, according to Diane D. Davey, M.D., professor of pathology and associate dean of graduate medical education at the University of Central Florida College of Medicine. Many providers don’t yet offer the option for HPV testing alone.

Any of these strategies is a good option, says Melnikow. “The bottom line is, screening is good, and women should get screened.” 

Evidence shows that in people 65 and older who had regular screenings throughout their lives, cervical cancer is rare. The USPSTF and American Cancer Society agree that most women can stop cervical cancer screening at age 65. 

The exceptions are people who've had cervical cancer, who've had a serious precancerous lesion detected in the course of screening, who may have other risk factors such as a compromised immune system, or who haven't had regular screenings. If you're in one of those groups, talk with your doctor about how long you need to keep up regular screenings for cervical cancer.  

The Potential Harms of Screening

Pap and HPV tests themselves have few side effects. But any result apart from a negative one triggers a series of follow-up steps, depending on how serious the initial result seems, and what subsequent tests reveal.

Sometimes, however, an initial result that appears potentially worrisome is actually harmless. That's known as false-positive, and it can happen with both Pap tests and HPV tests. HPV tests, however, are linked with more false-positive results than Pap tests.

To get a sense of how big the risk for a false-positive is, consider these numbers: according to a comprehensive Cochrane review published in 2017, on average, the rate of precancerous cervical lesions is about 2 percent—or about 20 out of every 1,000 women who get screened. Out of that same thousand women, 99 will have a false-positive result if they opt for HPV test, while 95 will have false-positive result if they opt for a Pap test.

Another study, published in JAMA in 2018, found that estimates of false positives ranged from 6.6 to 7.4 percent for HPV tests, compared with 2.6 to 6.5 for Pap tests.

And according to Schiffman, some HPV tests may detect types of the virus that are highly unlikely to cause cancer. In that scenario, even though the result of the test is positive, it shouldn’t be a reason to worry.

False-positive results can cause a great deal of unnecessary anxiety. They can also lead to unneeded follow-up tests. A key follow-up test is colposcopy, in which a doctor uses a magnifying scope to examine the cervix for precancerous or cancerous lesions. Sometimes a doctor may take a biopsy of tissue during the colposcopy. Risks can include bleeding, pain, discharge, and infection.

Finally, some treatments to remove precancerous lesions detected by screening carry risks as well. These include changes to the cervix that some research suggests may lead to fertility problems, including a greater risk of preterm birth in a subsequent pregnancy. This risk varies depending on the treatment type, Melnikow says, but it’s a potential risk that women need to be aware of—and is another reason to avoid testing more often than is recommended. 

Selecting a Screening Test

The most important thing to remember about cervical cancer screening is that the test you choose once you turn 30 isn’t as important as getting screened regularly. In addition, to comply with the Affordable Care Act, insurance plans must cover cervical cancer screenings.

Your decision may depend on which tests are available from your provider, how often you prefer to come in for screening, and how comfortable you are with false-positive results and the attendant follow-up testing. Remember, HPV testing and co-testing are more likely to cause a false-positive than a Pap test alone.

Co-testing specifically may be a good choice for women who haven’t been getting screened on a regular schedule, notes Davey. “If women aren’t getting screened as regularly as ideal, then it’s good to have both tests available.” 

Editor's Note: A previous version of this article stated that the HPV vaccine was almost 100 percent effective at preventing precancerous cervical lesions. The piece has been updated to reflect that the HPV vaccine prevents only precancerous cervical lesions caused by the strains of HPV included in the vaccine.