Cervical Cancer Is Preventable - The Importance of HPV Vaccination and Screening

The Cause of Cervical Cancer - A Virus Called HPV

Cervical cancer is caused by persistent infection with the human papillomavirus (HPV). HPV is transmitted through sexual contact, and according to Japan's Ministry of Health, Labour and Welfare, overseas reports indicate that 50-80% of sexually active women will be infected at least once in their lifetime - it is an extremely common virus. There are over 200 types of HPV, but only about 15 "high-risk" types cause cervical cancer, with types 16 and 18 accounting for about 70% of cervical cancers worldwide (U.S. National Cancer Institute). According to the WHO, about 90% of HPV infections are cleared naturally by the immune system within 1-2 years. However, in about 10% of women, the infection persists and progresses through precancerous lesions (dysplasia) to cervical cancer over a period of several years to more than a decade.

HPV Vaccine Effectiveness - The 9-Valent Vaccine Prevents 80-90% of Causes

The HPV vaccine prevents cervical cancer by blocking HPV infection. In Japan, the 9-valent vaccine (Gardasil 9) became part of the routine immunization schedule in April 2023. The 9-valent vaccine produces antibodies against HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58, covering HPV types that, according to Japan's Ministry of Health, Labour and Welfare, account for 80-90% of cervical cancer causes. Clinical trials have reported a high level of protection against precancerous lesions caused by HPV types 16/18 in vaccinated individuals. A large-scale Swedish registry study (Lei et al., 2020) reported that women who received the quadrivalent vaccine before age 17 had an 88% reduction in the risk of invasive cervical cancer.

Who Should Get Vaccinated and When

Routine vaccination targets girls from 6th grade through 1st year of high school, available free of charge through public funding. Since HPV is transmitted through sexual contact, vaccination is most effective before first sexual intercourse. The vaccination schedule is 2 doses (at 0 and 6 months) when starting before age 15, and 3 doses (at 0, 2, and 6 months) when starting at age 15 or older. As a catch-up program, women born between 1997 and 2007 (the generation that missed vaccination opportunities) can also receive publicly funded vaccination until March 2025. Even women who are already sexually active benefit from vaccination, as it protects against HPV types they have not yet been exposed to.

Vaccine Safety - The Reality of Side Effects

The most common side effects of the HPV vaccine are injection site pain (about 80%), swelling (about 30%), and redness (about 25%). Systemic side effects may include headache, fever, and fatigue lasting several days. In Japan, diverse symptoms (chronic pain, movement disorders, etc.) were reported after vaccination in 2013, leading to a temporary suspension of proactive recommendations. Subsequently, large-scale epidemiological studies both domestically and internationally concluded that no causal relationship existed between these symptoms and the vaccine, and proactive recommendations were resumed in April 2022. The WHO has repeatedly confirmed the safety of HPV vaccines.

How to Get Screened for Cervical Cancer

Even with HPV vaccination, regular screening is essential because infection with HPV types not covered by the vaccine remains possible. In Japan, cervical cancer screening every 2 years is recommended for women aged 20 and older. The standard screening method is a Pap test (cytology), which involves collecting cells from the cervix and takes only a few minutes. Municipal screenings are available free or at low cost. In recent years, HPV testing (which detects HPV DNA) combined with cytology has become more widespread, showing higher sensitivity for detecting precancerous lesions than cytology alone. For general lifestyle disease prevention, our article on the basics of preventing lifestyle diseases is also helpful.

What to Do If Dysplasia Is Found

If abnormalities are found during screening, further examination (colposcopy and biopsy) is performed. Dysplasia is classified as mild (CIN1), moderate (CIN2), or severe (CIN3). About 60% of CIN1 cases regress spontaneously, so follow-up observation every 3-6 months is standard. CIN2 may also regress spontaneously, but treatment is considered if it persists. CIN3 has a low probability of spontaneous regression, and cone biopsy (surgical removal of a cone-shaped portion of the cervix) is the standard treatment. Since cone biopsy preserves the uterus, pregnancy after the procedure is possible. However, there is a slightly increased risk of preterm birth, requiring careful management during pregnancy. For concerns about fertility planning, our article on fertility and future planning is also helpful.

HPV Vaccination for Men

HPV also infects men and can cause penile cancer, anal cancer, and oropharyngeal cancer. Additionally, men carrying HPV can transmit it to female partners through sexual contact. Many countries including Australia, the United States, and the United Kingdom provide routine HPV vaccination for both males and females, and reductions in HPV infection rates through herd immunity have been reported. In Japan, routine vaccination for males has not been implemented as of 2025, but voluntary vaccination (self-funded) is available. From the perspective of protecting a partner's health, male vaccination is worth considering. For coping with anxiety, our article on managing anxiety in daily life is also helpful.

Cervical Cancer Is a "Preventable Cancer"

Cervical cancer is one of the few "preventable cancers" - the causative virus has been identified, it can be prevented with a vaccine, and it can be detected and treated at the precancerous stage through screening. In Australia, high HPV vaccination rates and widespread screening are predicted to bring the annual incidence of cervical cancer below 4 per 100,000 women by 2028 - the level the WHO uses as its threshold for elimination as a public health problem (Hall et al., 2019). In Japan too, the combination of vaccination and regular screening has the potential to eliminate cervical cancer. Once you turn 20, make screening every 2 years a habit, and if you have not been vaccinated, do not miss the catch-up vaccination opportunity.