Human papillomavirus, or HPV, is a group of over 200 viruses that are very common in humans. Most types do not cause any problems, however some can develop into diseases such as genital warts or cancer. HPV types known to cause cancer are classified as “high risk”. There are currently 14 known high risk HPV types, two of which, HPV16 and HPV18, are responsible for most HPV-related cancers. Thankfully we have the means to protect against these high-risk strains by way of the HPV vaccines. But how did we get to that point?
In the 1970s and 80s, Harald zur Hausen, German virologist, isolated HPV strains in cervical cancer tumours, and later the theory that HPV is a causal agent of cervical cancer was confirmed. Following zur Hausen’s work, HPV was found to cause other cancers including as anal, vulval, and oral. Zur Hausen proposed the idea of the HPV vaccine as a cancer prevention method in 1986, but was rejected by pharmaceutical companies as they believed the vaccine was not profitable. The HPV vaccine would not come until nearly two decades later. For his discoveries, and their impact on global health, Harald zur Hausen was awarded the 2008 Nobel Prize in Medicine. He continues to research infectious agents and their contribution to cancer.
In the late 1700s, Edward Jenner pioneered the first widely used vaccine, the smallpox vaccine. Following this, almost 100 years later, Louis Pasteur developed vaccines for chicken cholera and anthrax, beginning the “vaccine revolution” where vaccination was heralded and became compulsory. Throughout the twentieth century, great and famous achievements were made in the field of vaccines, such as diphtheria, measles, mumps, rubella, and polio vaccines. In general, vaccines work by training the body’s immune system to combat an infectious disease by introducing certain molecules from that pathogen (the thing that causes the disease) into the body. The immune system can then recognise these molecules if they later enter the body, already knowing how to fight it and prevent it from spreading. Vaccines are incredibly important for public health, have saved millions of lives, and have almost eradicated many infectious diseases that previously wiped out entire communities.
The HPV vaccine was first developed by the University of Queensland in Australia by Professors Ian Frazer and Jian Zhou. In 1990, Frazer and Zhou began to synthesise particles that mimicked HPV, from which the vaccine would later be made. These particles are called “virus-like particles” (VLPs), and are small particles that contain proteins from the outer layer of the HPV virus. VLPs do not contain any of the DNA, dead or live, from the virus, and therefore cannot cause an HPV infection or related cancer. Introducing these VLPs into the body via injection stimulates the body to create the antibodies needed to fight it and clear it from the body. As the VLP closely resembles the actual virus, these antibodies will attack and remove HPV if it enters the body. This method of vaccination is highly effective, as the VLPs cause high levels of antibody production.
In 1991, Frazer and Zhou’s findings were first presented to the scientific community. After seven years of design and testing, the first human trials for the vaccine, named Gardasil, were completed. This vaccine prevented four high-risk HPV types (HPV 6, 11, 16, and 18), which would target over 70% of cervical cancer cases. In 2006, following extensive clinical trials which found the vaccine to provide almost 100% protection against HPV 16 and 18, the vaccine was approved for use by Australia and the USA, and by 2007 the vaccine was approved in 80 countries.
Since then, two further vaccines have been approved: a bivalent vaccine called Cervarix approved in 2007 that prevents two HPV types (HPV16 and 18) and a nonavalent vaccine called Gardasil 9 in 2014 that protects against nine HPV types (HPV 6, 11, 16, 18, 31, 33, 45, 52, and 58). As of October 2019, 100 countries worldwide vaccinate against HPV as part of their regular vaccine schedule.