What is human papillomavirus?

What is human papillomavirus?

Human papillomavirus (HPV) is a virus that is primarily spread through sexual contact. There are more than 100 types of HPV and can be classified into low- or high-risk types based on the disease they cause. Low-risk HPV types (i.e. type 6 and 11) can cause small harmless growths (warts) on the genitals and in the throat, while high-risk HPV types (i.e. type 16 and 18) are the main causes of cervical cancer in women.

Who does it affect?

HPV infection is the most common viral infection of the reproductive tract and affects both men and women. It is estimated that 80% of sexually active women are infected at least once in their lifetime. The peak time for acquiring HPV infection is during adolescence, shortly after becoming sexually active. Although rare, it is also possible for a mother with HPV to pass the infection to her baby during childbirth. While the majority of HPV infections do not pose a problem, a small proportion of infections can persist over many years and progress to cancer if not treated. Each year, approximately half a million women globally are diagnosed with cervical cancer, with most of these cases occurring in resource-poor countries.

What are the symptoms of HPV infection and how is it diagnosed?

HPV infections typically do not have symptoms, and so the individual is often unaware they are infected. However, some people may notice abnormal growth on the genitals, and in more serious cases (i.e. cancer), there may be bleeding and/or pain after sex, abnormal period, and vaginal bleeding or discharge pain in the pelvis. It could take a decade from initial infection to the development of cervical cancer if left untreated. There are HPV tests to screen for cervical cancer (i.e. Pap smear and HPV DNA testing) which are highly effective.

How can you prevent HPV infection and cervical cancer?

Protection against HPV infection is best achieved through HPV immunisation. There are three different HPV vaccines available currently and all are safe and extremely effective. It is recommended to be given during late childhood or early adolescence, prior to sexual debut. In Australia, 9vHPV (protects against the 9 most common types) is given to all girls and boys aged 12-13 years old. In this age group, HPV vaccine is given as two doses while in older women (>15 years old) it is given as three doses. Prevention of HPV infection and cervical cancer should include a combination of vaccination and cervical cancer screening (starting from 25 years of age, and every 5 years if the result is normal).

What are the gaps in research we are trying to fill?

The HPV vaccines are expensive making it hard for low resource countries to afford them. We are finding ways to make HPV vaccination more accessible for resource-poor countries as they have the highest burden of cervical cancer. One exciting strategy to alleviate the cost and logistics of HPV vaccination programs is to reduce the number of doses given, with the possibility of only one dose being sufficient to provide long-term protection. We have provided some of the first evidence of the potential benefit of using only one dose of HPV vaccine in Fiji and Mongolia. 

What research is taking place now?

We are conducting both public health and laboratory-based research to answer a number of questions relating to HPV vaccination. We are conducting several studies in resource-poor countries to determine how common HPV infection is, and what the impact would be following the introduction of HPV vaccination. There are ongoing studies (led by Prof Fiona Russell) on the effectiveness of a single dose of HPV after 7 years in Fijian women. In Vietnam, we are undertaking innovative studies (led by Prof Kim Mulholland) to reduce HPV transmission by vaccinating specific high-risk populations (i.e. those with multiple sexual partners). A major program of research is aimed at applying cutting-edge technologies to better understand the immune response following a single dose of the HPV vaccine and provide evidence to support the use of this schedule.

References

Arbyn M, Weiderpass E, Bruni L, et al. Estimates of incidence and mortality of cervical cancer in 2018: a worldwide analysis. Lancet Glob Health. 2020;8:e191-e203
DOI: doi.org/10.1016/S0140-6736(20)30157-4

Authors

A/Prof Paul Licciardi (Team Leader) and Dr Ryan Toh (Research Officer) are part of the New Vaccines group at MCRI. They are researching ways to make the HPV vaccination more accessible and in doing so, reducing the burden of cervical cancer.