The German virologist who discovered the link between human papilloma virus and cervical cancer will share this year’s Nobel Prize for Physiology and Medicine. Prof. Harald zur Hausen has been studying HPV and cervical cancer for more than thirty years; his work paved the way for the development of vaccines against HPV.
The award comes at a time when controversy is raging over the HPV vaccine in the United States. Since Merck's Gardasil vaccine was approved by the FDA in 2006, mandatory vaccination programs have been proposed in several states.
The efficacy of the vaccine in preventing two strains of HPV that cause the majority of cervical cancer is not in dispute. However, these two strains only account for 70% of cervical cancers, with the remainder being linked to other strains. Some public health professionals wonder whether Merck’s aggressive PR campaign has sold the public on a vaccine that, while effective, may not deliver enough public health benefits to justify its considerable cost. Gardasil costs upward of $360 U.S. for the full three-shot treatment.
In an interview following his award, zur Hausen criticized pharmaceutical companies for pricing the HPV vaccine out of reach of those who need it most. He told a German newspaper that the vaccine was “much too expensive." [11]
Zur Hausen’s Nobel Prize is a reminder that, despite the public policy controversy, there is overwhelming scientific consensus that HPV is the cause of cervical cancer. The question then becomes how best to combat the threat.
When zur Hausen first proposed a link between HPV and cancer in the early seventies, the scientific community was very skeptical. At the time, experts thought herpes simplex caused cervical cancer. Ultimately, zur Hausen won his critics over by identifying cancer-causing strains of HPV, linking the pathogen to cancer in the real world, and explaining how HPV infection leads to cervical cancer. Zur Hausen identified the strains of HPV virus that cause the majority of cervical cancers, namely HPV16 and HPV18. Then he did the epidemiological research to prove that women infected with HPV went on to develop cancer. Finally he explained how the HPV virus leads to cancer—virus genes insinuate themselves into cervical cells, causing the cells to divide abnormally.
To date, over 100 strains of HPV have been sequenced, but only about 15 are known to cause cervical cancer.
HPV presents a global public health challenge for men and women. Each year, 470,000 women around the world contract cervical cancer. The disease claims 230,000 lives annually, with 8 out of 10 of these deaths occurring in developing countries. Two million three hundred thousand women are living with cervical cancer in the world today. Among women with cervical cancer, 99.7% test positive for HPV. Between 50% and 80% of sexually active adults will eventually contract HPV. Most people will recover spontaneously within two years, but persistent infection can lead to cancer.
Cervical cancer is by far the most common HPV-related cancer, but men are also at risk, though statistically they are less likely to succumb than women. HPV has been shown to cause cancer of the penis, anus, and esophagus. In total, human papilloma viruses cause approximately 5% [12] of all cancers worldwide.
In clinical trials [12], the Gardasil vaccine was 95%-100% effective in preventing pre-cancerous changes in the cervix. The vaccine was also 99% effective in preventing genital warts. Epidemiological studies show that women are most likely to be infected between the ages of 15 and 22.
Because the vaccine is most effective when administered before exposure to HPV, the vaccine is recommended for girls aged 11-12. The vaccine is approved for women up to the age of 26. Though HPV affects both sexes, the public policy debate in the United States has centered almost exclusively on vaccinating girls.
Zur Hausen believes that both sexes should be vaccinated for HPV. If everyone gets vaccinated, HPV16 and HPV18 might eventually be eradicated like smallpox and polio. Universal smallpox vaccination was so effective that the vaccine became unnecessary. Gardasil only protects against two strains of cancer-causing HPV and two strains that cause genital warts. So, the vaccine is at best an imperfect solution. HPV is present in 99.7% of cervical cancer cases, so a vaccine that covered more strains could be even more beneficial.
With any luck, the Nobel Prize will stimulate publicly-funded research into new and better HPV vaccines. Governments should cooperate to out-compete the pharmaceutical giants who control the vaccine market. The goal should be to develop a superior alternative to Gardasil that can be distributed at low cost to everyone who needs it.
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- Emily Alexander, There's More to HPV Prevention than Gardasil [13]