Behind The Medical Headlines

NEW PATIENT/PUBLIC SUMMARY ARTICLE No.2 (pilot): Vaccination for cervical cancer

• Mr G McAlister, adapted from the original clinical review article by Professor Ian Frazer, University of Queensland, Australia

Summary

We are currently piloting the production of plain English ‘Patient/Public’ summaries of original clinical review articles published on the BTMH website in order to increase public access to, and understanding of, the clinical content of these articles. Please access this short Patient/Public summary of Professor Ian Frazer’s overview of Vaccination for Cervical Cancer, and complete the short survey at the end of this article in order to provide us with your feedback. (Image - © istockphoto.com)

Declaration of interests: No conflict of interests declared

Patient/public version of article

Vaccination for cervical cancer

(Adapted from the original clinical article by Professor IH Frazer, University of Queensland, Australia. Professor Frazer is acclaimed for his work in developing the world’s first cervical cancer vaccine.)

Introduction

Cancer of the cervix (the neck of the womb) kills a quarter of a million women a year and is caused by persistent infection of the lining of the cervix by some of the human papillomavirus family of viruses. There are more than 200 of these related viruses. While many do not cause any disease, or at worst cause genital warts, about ten are deemed high-risk viruses because persistent infection can lead to the development of cervical cancer and can contribute to about 20% of head and neck cancers.

Infection and screening

Infection with high-risk human papillomaviruses is mainly acquired through sexual intercourse and occurs in at least 30% of young women and men, generally before the age of 25. To date, attempts to prevent cervical cancer have focused on screening through the Pap smear test, during which the cervix is gently scraped with a swab to obtain a sample of cells lining the cervix. This sample is then smeared on to a glass slide and examined under a microscope to identify any cancerous or pre-cancerous changes to these cells. Such screening is very effective, but relies on regular screening (a single smear test will only identify abnormalities in about 50% of women carrying a high-risk virus) and cannot always be financially supported in all countries.

Vaccine development

Following the identification of a link between the high-risk human papillomaviruses and cervical cancer in the early 1980s, attempts were made to develop vaccines to prevent and treat this form of cancer. Commercial vaccines to prevent infection with high-risk human papillomaviruses have now been developed, using genetically engineered virus-like particle technology. This technology has resulted in the development of safer artificial vaccines using the DNA of another organism to stimulate antibody production and an immune reaction, rather than injecting an individual with a ‘live’ vaccine (the older style of vaccine introduced a small amount of the related virus into the bloodstream in order to stimulate such a reaction). These vaccines are known as recombinant vaccines and are considered to have fewer risks of side effects than ‘live’ vaccines.

Safety and effectiveness

The current cervical cancer vaccines have been tested extensively during their 15-year development process, in clinical trials involving more than 25,000 young women. These vaccines include genetically engineered virus-like particles for two of the highest-risk human papillomaviruses, and have the potential to prevent about 70% of cervical cancers worldwide. The vaccines have been demonstrated to be about 95% effective at preventing infection with these high-risk viruses and 100% effective at preventing human papillomavirus-associated disease over a five-year follow-up period.

The best time for maximising the effect of immunisation is between the ages of 9 and 26 in young women, although some countries have also licensed the vaccines for use in boys. An added benefit of early immunisation is that the immune response to the cervical cancer vaccine is best before puberty. Vaccination against cervical cancer requires three immunisations over a period of 6-12 months.

The development of vaccines against cervical cancer will form another weapon in the fight against this disease and will be used alongside Pap smear screening programmes. However, in countries in which resources are scarce, vaccination is likely to be the only measure available to reduce cervical cancer.

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