Human papillomavirus (HPV) is the most commonly sexually transmitted virus in the world, infecting 75% of sexually active adults in their lifetime1.
HPV infection has a dramatic impact on global health, with more than 500,000 cervical cancer cases diagnosed worldwide each year, the vast majority of which (around 85%) occur in the less developed regions2 where no screening programs are available, and women are diagnosed at late stages. Globally, cervical cancer causes more than 260,000 deaths each year2.
HPV also causes genital warts and other malignancies such as head and neck cancer, and men get HPV-related throat cancer as often as women get HPV-related cervical cancer.
Making the HPV Vaccine: Challenges and Persistence
During a recent Wistar event, thought leaders in the field of HPV vaccines, Dr. Kathrin Jansen, Pfizer senior vice president and head of Vaccine Research and Development, and Dr. Iona Munjal, Pfizer director of Clinical Research and Development, laid the historical groundwork in their roles to develop, design and roll out the world’s first HPV vaccine.
“This is the story of great scientific discovery, grit and persistence, and the breaking of dogmas,” said microbiologist and vaccinologist Dr. Jansen.
HPV was identified as the root cause of cervical cancer in the 1990s by German virologist professor Harald zur Hausen, who went on to win a 2008 Nobel Prize in Physiology or Medicine for revolutionizing cervical cancer research by discovering HPV DNA in cervical cancer biopsies. A seminal study in 1999 confirmed that HPV is a necessary cause of cervical cancer, as virtually all cervical lesions (99.7%) contain HPV DNA3.
According to Jansen, the early phases of vaccine development were surrounded by skepticism and it took much perseverance to overcome the technical challenges. In the process, she and the other scientists working in the HPV field broke some scientific dogmas, showing for example that, contrary to the common assumption that cancer development by HPV takes decades, it occurs relatively quickly (within 1-5 years from infection), which allowed for testing the vaccine effectiveness in a reasonable timeframe.
In several clinical studies the vaccines currently available showed excellent safety profiles and a remarkably high efficacy against cervical cancer. Complete prevention of virus infection, referred to as sterilizing immunity, was also demonstrated by the HPV vaccine, breaking another dogma that considered this an elusive goal.
Vaccine redemption
Despite its extraordinary effectiveness in preventing cervical cancer, the HPV vaccine had to fight some initial backlash caused by prejudice and confusion.
“HPV being a sexually transmitted disease overshadowed the importance of this vaccine as a cancer prevention strategy, which is far more significant and the ultimate goal of vaccination,” said Munjal, who is a pediatric infectious disease doctor. “This vaccine was 90% effective against HPV and we had so much joy because it can eventually eradicate HPV-related cancers. But we just saw the numbers and missed the story. We had to get back to basics and normalcy regarding this vaccine. Pediatricians had to give this vaccine as they did the rest of the recommended vaccines — treat it exactly the same. It’s a revolutionary change that we’ve lived through and learned from.”
That the vaccine protected against cancer and genital warts made it a hot button issue tied to sexually transmitted disease and the myth that the vaccine would somehow encourage or endorse promiscuity among teenagers.
Munjal also discussed different vaccine rollout strategies in other countries.
“Right now HPV vaccine uptake is at 50%, but in Australia and the United Kingdom, the disease burden is dropping,” said Munjal. “By 2030, Australia will cure cervical cancer by 90%. They were able to do it because it’s a school-based health campaign which shows the effectiveness of bringing care to where people are.”
In 2006, Merck’s HPV vaccine Gardasil was approved in the U.S. It protects against HPV types 6, 11, 16 and 18, preventing 70% of cervical cancers, and the majority of HPV-induced cancer cases and genital warts. In 2014, an expanded vaccine Gardasil 9 was approved.
One of the most important advances in cancer prevention, the HPV vaccine is safe and effective. It is recommended for people from 11 to 26 years old and available to adults up to 45 years old who are at risk. Yet, vaccine rates in the U.S. for girls and boys from 13 to 17 years old still hover between only 48.6% to 51%1. About 14 million people contract HPV each year in the U.S., and 92% of these infections are caused by vaccine-preventable strains1.
The United States has the capability to eradicate HPV and by doing so has the opportunity to wipe out cervical cancers and six other cancers related to HPV. We still need new methods to screen for HPV and improve treatment on pre-cancerous lesions. The Healthy People 2020 campaign wants complete vaccination for more than 80% of female and male teenagers ages 13-15 by 20204.
- Centers for Disease Control (CDC)
- International Agency for Research on Cancer (IARC)
- Human papillomavirus is a necessary cause of invasive cervical cancer worldwide. 1999 Walboomers J.M. et al, J Pathol.
- healthypeople.gov