Dr Olga Sambolska*

Human papillomavirus (HPV) infection is the main cause of almost all cases of cervical cancer. While most HPV infections are harmless and transient, a small proportion persist and may lead to precancerous cervical changes and, eventually, cervical cancer. Understanding HPV tests, Pap smears, and HPV vaccination helps women take an active role in preventing cervical cancer. 

What is Human Papillomavirus (HPV)?

HPV is a large family of viruses, with more than 200 known types. Around 40 of these infect the genital and anal areas and are transmitted through sexual contact.

HPV types are classified as:

• Low-risk HPV (types 6 and 11) causes genital warts but is not associated with cancer. 
• High-risk HPV (such as types 16, 18, 31, 33, 45, 52, 58) can cause cervical cancer and several other cancers. 

HPV types 16 and 18 are responsible for approximately 70 per cent of cervical cancer cases worldwide.

HPV infection and immune clearance  

HPV infects the superficial cells of the cervix, usually at the transformation zone, where glandular and squamous cells meet. In most women, the immune system suppresses and clears the virus naturally within 6-24 months.

HPV becomes dangerous only when:

• The infection is caused by a high-risk HPV type.
• The virus persists for several years.  
• Viral genes interfere with the body's normal cell-cycle control.

Persistent infection allows HPV to produce proteins (E6 and E7) that disrupt tumour-suppressor pathways, leading to abnormal cell growth.

From HPV infection to cervical cancer 

Cervical cancer does not develop suddenly. It usually follows a gradual process:

1. Persistent high-risk HPV infection
2. Development of precancerous changes (CIN - cervical intraepithelial neoplasia)
3. Progression to invasive cervical cancer over 10–20 years if left untreated

This long timeline is one of the main reasons why cervical cancer screening is so effective.

What is a Pap smear? 

A Pap smear examines cervical cells under a microscope to identify abnormal cell changes that may be caused by HPV.

Pap smear results may include:

• Negative for intraepithelial lesion or malignancy (NILM): Normal cervical cells
• ASC-US: Atypical cells of unclear significance
• LSIL: Mild abnormalities, often related to a temporary HPV infection
• HSIL: Significant precancerous changes requiring prompt evaluation
• Cancer: Rare, and usually detected only when screening has not been performed regularly

A normal Pap smear does not necessarily mean HPV is absent. It simply means that, if HPV is present, it has not caused detectable cell changes at that time.

HPV test: how is it different?

Unlike a Pap smear, an HPV test detects DNA from high-risk HPV types. It answers a different question: 

"Is a high-risk HPV virus present?"

Key points:

• HPV testing identifies women at increased risk before abnormal cell changes develop.
• A negative HPV test is highly reassuring.
• A positive HPV test does not mean cancer. It simply indicates that closer follow-up may be needed.
• Many screening programmes now recommend primary HPV testing or co-testing (Pap smear and HPV test together), particularly for women aged 30 years and older.

Why does cervical cancer screening vary by age?

Young women commonly clear HPV infections naturally.

Older women are more likely to develop persistent HPV infection.

For this reason:

• Frequent screening is generally avoided in younger women to reduce unnecessary treatment.
• Longer screening intervals are considered safe after a negative HPV test.
• Doctors recommend screening based on each woman's individual level of risk rather than convenience.

HPV vaccination: how does it work? 

HPV vaccines are preventive, not therapeutic. They do not treat existing HPV infections or abnormal cervical cell changes.

The vaccine contains virus-like particles that stimulate the immune system to produce protective antibodies without causing infection.

What does the HPV vaccine protect against?

Modern HPV vaccines protect against:

• HPV 16 and 18, the two highest-risk cancer-causing types
• Several additional high-risk HPV types
• Low-risk HPV types that cause genital warts (depending on the vaccine)

Vaccination prevents infection with the HPV types responsible for most cases of cervical cancer.

Timing and effectiveness:

• HPV vaccination is most effective before the onset of sexual activity.
• It still provides benefits after sexual activity has begun.
• HPV vaccination does not replace regular Pap smears or HPV testing.

Common misconceptions about HPV and cervical cancer:

"If I test positive for HPV, I have cervical cancer."

False. HPV infection is common, while cervical cancer is relatively rare.

"A normal pap smear means I don't have HPV."

Not necessarily. HPV may be present without causing abnormal cervical cells.

"Women who have received the HPV vaccine no longer need screening."

Incorrect. Vaccinated women should continue regular cervical cancer screening.

"Testing positive for HPV means I was recently infected."

Not always. HPV can remain dormant for many years before being detected.

Key messages for women

• HPV infection is common, but cervical cancer is largely preventable.
• Pap smears detect abnormal cervical cells, not the virus itself.
• HPV testing identifies women at increased risk before disease develops.
• HPV vaccination helps prevent infection but does not replace routine screening.
• Long-term follow-up, not fear, is the appropriate response to a positive HPV test.

Summary

HPV-related cervical cancer is one of the clearest examples of successful preventive medicine. With HPV vaccination, regular cervical cancer screening, and appropriate follow-up, cervical cancer has become one of the most preventable cancers affecting women. — Family Medical Practice 

*Dr Olga Sambolska graduated from Lviv National Medical University in 1996 and began her medical career at the Volyn Regional Maternity Hospital in Ukraine. Since 1998, she has been a registered obstetrics and gynaecology doctor, providing healthcare to women in relation to pregnancy, birth control, menopausal issues, contraception, menstrual cycle disorders and sexually transmitted diseases. She is fluent in English, Ukrainian, Polish and Russian.

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