A Tale Of Two Vaccines

Vaccines that prevent cancer are now a reality. Yet, not everyone has jumped at the opportunity to get immunized. Jeremy Chan investigates why.

AsianScientist (Aug. 10, 2017) – In 1911, Peyton Rous, a scientist at the Rockefeller University in New York City, made an unusual observation. By mashing up chicken tumors, filtering the pulp, and injecting the flow-through fluid into a healthy chicken, he could effectively cause cancer in the unfortunate recipient.

Rous showed that a filterable agent—a virus—within the donor fluid was responsible for tumor growth in the new host. The implications of his discovery were revolutionary; if a virus could cause cancer, then a vaccine should be able to stop cancer from ever showing up.

During vaccination, a weakened version or a fragment of the offending virus is delivered to the recipient’s immune system. This primes the immune system to destroy the real McCoy—a live virus—upon infection.

As the fields of oncology and virology converged, researchers eventually found compelling evidence for a link between hepatitis B virus (HBV) infection and liver cancer, and between human papilloma virus (HPV) infection and cervical cancer. Vaccines against both viruses are now available, boasting protection rates upwards of 90 percent in uninfected individuals. However, the trajectories of these two vaccines could not have been more different.

Two vaccines, two different trajectories

When discussing vaccine coverage, the concept of herd immunity is important. Basically, if enough people in a population get vaccinated, the chance of any individual catching an infection is drastically reduced. Hence, those who cannot obtain the necessary vaccines, or who refuse vaccination, are the weakest links in the chain.

Because vaccines are the most effective when administered before infection, vaccination carried out early in life is critical in tackling the spread of disease. Before the HBV vaccine was approved in 1981, one in 20 children under the age of five was infected with HBV. Today, the HBV vaccine is scheduled during infancy in 185 countries and the proportion of infected children has plunged to 1.3 percent.

Unfortunately, the success of HBV vaccination did little to engender enthusiasm for HPV vaccination. Introduced in 2006, the HPV vaccine is targeted at girls before they become sexually active. In a decade, only 1.4 percent of the global female population has been immunized against HPV, and Asian women are among the least protected. Herd immunity against HPV, and by extension cervical cancer, is thus virtually non-existent.

Vexing vaccine economics

The human right to health is universal, yet barriers to healthcare exist and the burden of disease often falls disproportionately on the poor. Eighty-five percent of new cervical cancer cases occur in the developing world, but 70 percent of immunized women are from high income countries.

Evidently, HPV vaccine coverage segregates along economic lines. The full three-shot dose of the HPV vaccine—Gardasil—costs up to US$450; a hefty sum when measured against the GDP per capita in many Asian countries which averages at US$6,205. In comparison, three doses of the HBV vaccine, Engerix-B, cost US$180.

“The high cost of the HPV vaccines is the primary barrier for controlling HPV-associated diseases,” said Dr. Liu Shih-Jen, an investigator at the National Institute of Infectious Diseases and Vaccinology in Taiwan.

Public-private partnerships that shape the market for HPV vaccines can make vaccination more affordable. For example, the Global Alliance for Vaccines and Immunization (GAVI), together with UNICEF, secured HPV vaccines from Merck & Co. and GlaxoSmithKline for under US$5 per dose via a public tender process. Under GAVI’s HPV demonstration program, Bangladesh, Cambodia, Indonesia and Laos qualify for financial support.

Entering the internet age

Apart from price, the internet may be responsible for the differing popularity of the HPV and HBV vaccines. Just as a virus is easily transmitted from one individual to the next, information is easily disseminated on the World Wide Web. Regrettably, misinformation also goes viral with relative ease.

“The internet has helped but also hurt the general impact of vaccines,” said Dr. Sharifa Ezat Wan Puteh, a professor at the National University of Malaysia’s Department of Community Health.

For example, when rumors circulated online that the HPV vaccine was unsafe and that it encouraged sexual promiscuity, Malaysia’s health ministry and religious authorities had to issue a religious ruling dispelling these falsehoods.

“The internet has helped but also hurt the general impact of vaccines.”

“Authorities need to send a strong health promotion message on the benefits of vaccines. This can be in the form of vaccine advocators, special advertisements or general public road shows on vaccinations and their benefits,” Sharifa Ezat told Asian Scientist Magazine.

She also noted that the Malaysian government’s strong support of HPV vaccination was, in part, due to a prior local study estimating the economic burden of cervical cancer in Malaysia. Evidence-based reporting of the safety and effectiveness of HPV vaccines further convinced the general public of the benefits of immunizing against cervical cancer.

Vaccines are a remarkable development in the prevention of cancer. But potent as they may be, their broad acceptance hinges on an understanding of psychology and effective communication. Arguably, the long-drawn-out battle against cancer is not just fought in the sterile rooms of clinics and hospitals—it is won or lost in the hearts and minds of people.

This article was first published in the July 2017 print version of Asian Scientist Magazine. Click here to subscribe to Asian Scientist Magazine in print.


Copyright: Asian Scientist Magazine.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Jeremy received his PhD from Nanyang Technological University, Singapore, where he studied the role of the tumor microenvironment in cancer progression.

Related Stories from Asian Scientist