HPV Infection and Cervical Cancer Prevention
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Direct answer
Human papillomavirus (HPV) is a DNA virus whose persistent infection with high-risk types, mainly types 16 and 18, causes nearly all cases of cervical cancer. Most infections clear spontaneously, so cancer develops only after years of persistence through precancerous lesions called cervical intraepithelial neoplasia. Prevention rests on HPV vaccination, screening with cytology or HPV testing, and treatment of precancerous lesions.
What you must remember
- High-risk types: HPV 16 and 18 cause the majority of cervical cancers, and types 31, 33 and 45 are also high risk.
- Low-risk types: HPV 6 and 11 cause genital warts and recurrent respiratory papillomatosis, not cervical cancer.
- Oncoproteins: E6 promotes degradation of p53, and E7 inactivates the retinoblastoma protein.
- Precursor lesion: cervical intraepithelial neoplasia, graded CIN 1 to CIN 3, with CIN 2 and 3 as the targets for treatment.
- Vaccine schedule: WHO accepts one or two doses for girls aged 9 to 20 years and two doses for women over 21; three doses are kept for immunosuppressed people, including those with HIV. India's national programme from 2026 uses a single dose for 14-year-old girls.
- Screening tests: cytology, HPV DNA testing and visual inspection with acetic acid in low-resource settings.
- Other cancers: anal, vulval, vaginal, penile and oropharyngeal cancers are also linked to HPV.
- Treatment of CIN 2 and 3: excisional procedures such as LEEP or cold knife conization, or ablation in suitable cases.
From infection to treatment
A 34-year-old woman with a high-risk HPV result on a screening test needs a stepwise pathway. Each step confirms or excludes a precancerous lesion before treatment is offered.
- Primary screening: cytology, HPV DNA testing or visual inspection with acetic acid is performed, depending on the setting and programme.
- Triage: HPV-positive women with abnormal cytology are referred for colposcopy, while HPV-positive women with normal cytology are followed up at a defined interval.
- Biopsy: colposcopy-directed biopsy establishes the grade of the lesion as CIN 1, 2 or 3.
- Treatment: CIN 2 and 3 are removed by excision or ablated, and the margins are checked on histology.
- Follow-up: repeat testing after treatment detects persistent or recurrent disease.
Screening is most useful in women who have not been vaccinated, and the strategy changes with the local resources. The visual method suits primary health settings, whereas cytology and HPV testing need laboratory support.
Where the exam tries to catch you
Questions on this topic usually test the risk types, the vaccine schedule and the difference between screening tests.
- Trap: every HPV infection leads to cervical cancer. Correct: most infections clear spontaneously, and cancer needs persistent high-risk infection over many years.
- Trap: HPV 6 and 11 cause cervical cancer. Correct: they cause genital warts and recurrent respiratory papillomatosis, while 16 and 18 cause most cancers.
- Trap: the vaccine is given only after the first sexual contact. Correct: it works best before exposure, which is why girls aged 9 to 14 years are the primary target group.
- Trap: a Pap smear detects the virus. Correct: cytology detects cellular changes, whereas HPV DNA testing detects the virus itself.
Frequently asked questions
Which HPV types cause most cervical cancers?
HPV types 16 and 18 cause the majority of cervical cancers worldwide. High-risk types 31, 33 and 45 account for most of the remainder. Types 6 and 11 are low risk and cause genital warts rather than cancer.
What is the mechanism of HPV oncogenesis in the cervix?
The E6 and E7 oncoproteins drive cervical carcinogenesis. E6 promotes degradation of p53, while E7 inactivates the retinoblastoma protein. Together they disrupt cell cycle control and allow infected cells to accumulate further mutations.
What is the WHO HPV vaccine schedule?
The WHO accepts a single-dose or two-dose schedule for girls aged 9 to 20 years, with two doses six months apart for women over 21. Three doses are used for immunosuppressed people, including those with HIV. India launched a single-dose programme for 14-year-old girls in 2026, and vaccination is most effective before first exposure.
Why is visual inspection with acetic acid used for cervical screening?
Visual inspection with acetic acid is used because it is inexpensive and can be performed in primary health settings without laboratory infrastructure. Acetowhite lesions suggest precancerous change and prompt referral for colposcopy. It forms the basis of screening in many low-resource settings, including the national screening programme in India.
Does HPV cause oropharyngeal cancer?
HPV, particularly type 16, causes a rising proportion of oropharyngeal cancers, especially of the tonsils and base of tongue. These tumours are typically p16-positive on immunohistochemistry. They have a different prognosis from tobacco-related oropharyngeal cancers, which is an important distinction.