Cancer Vaccines Move From ‘Far-fetched’ to Reality
PREVENTION BETTER THAN CURE, ESPECIALLY IN DEVELOPING COUNTRIES
It’s common knowledge that vaccines are given to healthy people to help prevent communicable diseases such as mumps, measles, chickenpox and many others, and have radically advanced the cause of global health. These vaccines are usually weakened or killed pathogens (like viruses or bacteria) and train the immune system to defend the body against specific pathogens. A person must get the vaccine before the virus infects him or her; otherwise, the vaccine won’t work.
But less well known is the concept of harnessing vaccines to prevent or fight many varieties of cancer. The idea of a vaccine against cancer started more than half a century ago and since then, a better understanding of the role of the immune system against cancer, improved diagnostics, and better techniques and strategies for vaccine development have turned what was once an “outrageous and far-fetched hypothesis” into reality. Instead of attacking pathogens, cancer vaccines make the person’s immune system attack cancer cells. In other words, cancer vaccines are “biological response modifiers” that work by stimulating the immune system’s ability to fight infections and disease.
Cancer vaccines are either preventive (or prophylactic), intended to prevent cancer from developing in healthy people, or treatment (or therapeutic), intended to keep precancerous lesions under control, treat an existing cancer or help keep it from coming back. Particularly in developing economies, access to these vaccines is vital – not only to blunt illnesses themselves but also the high cost of treating them. Below is the “state of play” for cancer vaccines and a few global economic factors that will help place them into hospitals and clinics most in need.
Cancer prevention vaccines available today
HPV vaccine: Gardasil (also known as Gardisil or Silgard) and Cervarix protect against certain strains of human papillomavirus (HPV), including some that cause cervical cancer. (But they don’t prevent all types of cervical cancer, so it’s important for women to continue routine cervcervical cancer screening – Pap tests – according to recommended screening guidelines.)
These vaccines were first introduced in high-income countries in 2006; their use has been limited in low-income countries due to the high price and delivery logistics. Cervical cancer is the third most common cancer worldwide, and about 84 percent of cases occur in less-developed countries. It is the leading cause of death from cancer among women in developing countries, where it causes about 190,000 deaths each year. Women in developing countries disproportionately suffer from the burden of cervical cancer, but often their countries do not have the resources to establish screening programs for women at risk of the disease or the ability to treat precancerous lesions. In these countries, HPV vaccination is the primary prevention of cervical cancer, through vaccine provision by GAVI, the Vaccine Alliance. GAVI is an international organisation created in 2000 to improve access to new and underused vaccines for children living in the world’s poorest countries.
To reach all girls with the HPV vaccine, countries are piloting outreach programs and using alternative facilities. Some countries are also looking into the possibility of delivering HPV vaccine with other health interventions like deworming and menstrual hygiene education. A major step toward equal access to HPV vaccine, regardless of where a child lives, was last year’s negotiation of a record low price of U.S. $4.50 per dose. GAVI negotiated that price (which, according to GAVI, represents a two-thirds reduction on the current lowest public sector price) with vaccine manufacturers Merck and GSK.
Hepatitis B vaccine: More than 80 percent of liver cancer occurs in developing countries. Chronic infection with hepatitis B virus is the main risk factor for liver cancer worldwide. The World Health Organization (WHO) recommends that all infants receive the hepatitis B vaccine as soon as possible after birth, preferably within 24 hours. The common hepatitis B vaccine brands available today are Engerix-B (GSK), Recombivax HB (Merck), Elovac B (Human Biologicals Institute), Genevac B (Serum Institute) and Shanvac B (Shanta Biotechnics India). These vaccines are given by shots to the muscle in the arm.
The vaccine prevents hepatitis B virus infection, which ranges in severity from a mild illness lasting a few weeks to a serious long-term illness that can lead to liver disease or liver cancer. Therefore, the hep B vaccine protects against liver cancer, which is among the most lethal cancers. Although it is sixth in incidence worldwide, it is third in mortality, after lung and stomach cancers. The first commercial hepatitis B vaccine was approved in the United States in 1981. The wholesale cost is between U.S. 58 cents and $13.20 per dose. As of 2013, 183 United Nations Member States vaccinate infants against hepatitis B as part of their vaccination schedules and 82 percent of children worldwide received the hepatitis B vaccine.
Cancer treatment vaccines available today
Bacillus Calmette–Guérin (BCG) is a vaccine primarily used against tuberculosis. It was first used in 1921 and is very successful against tuberculosis meningitis, but its success against pulmonary tuberculosis seems to vary with geography. Over the past three years, there has been a decline in global availability of BCG vaccine. In light of this shortage, WHO has prepared a prioritized list of countries with the highest TB rate per 100,000 population and called on vaccine manufacturers to rapidly increase the supply of BCG vaccine to the global market. The ministry of health/department of health in these countries buys the vaccine from the manufacturers. Using this same BCG vaccine in higher doses is effective in helping to prevent or delay bladder cancers from growing back or spreading into the deeper layers of the bladder.
Sipuleucel-T (Provenge) is the only vaccine approved in the U.S. to treat cancer. It is used to treat advanced prostate cancer that is no longer being helped by hormone therapy. The vaccine does not cure prostate cancer, but has been shown to help extend patients’ lives by several months, on average. Clinical trials are being done to investigate whether the vaccine can be used in men with less advanced prostate cancer. Prostate cancer is an important public health concern in Western countries and an emerging malignancy in developing nations. The treatment cost was $93,000 in the U.S. when the vaccine was first approved, but rose to over $100,000 in 2014.
CimaVax EGF is a vaccine being developed in Cuba for non-small cell lung cancer (NSCLC). In clinical trials, Cimavax-treated lung cancer patients who were younger than 60 years old survived an average of 18.5 months compared to 11 months in the control group. The younger vaccinated patients survived significantly longer than controls, who survived an average of 7.6 months. A phase 3 trial is currently in progress in Cuba. The United States is currently at work developing two lung cancer vaccines of its own – Tecemotide BLP 25 for non-small cell lung cancer and GVAX. NSCLC accounts for approximately 85 percent of all cases of lung cancer. Smoking is by far the leading risk factor for lung cancer, and although smoking rates in the United States have been slowly declining, tobacco use is on the rise in several developing countries.
The cost-effectiveness of vaccines
It is often said that prevention is better than cure. Total cost for treatment at six months after diagnosis for cervical cancer varies from $3,000 up to $45,000. For comparison, the preventive vaccine costs between $4.50 per dose in GAVI countries to $150 per dose in developed countries. And the HPV also prevents other cancers, such as penile, vaginal, oral and anal.
For patients not covered by health insurance, liver cancer treatment can cost up to $50,000 or more for targeted radiation therapy. It can cost about $50,000 or more for partial removal of the liver, $150,000 or more for a year of treatment with targeted therapy drugs, and more than half a million dollars if a transplant is required. Meanwhile, the most expensive hepatitis B vaccine costs around $13 per dose.
The significant differences in cost of treatment versus vaccination make the HPV and hepatitis B vaccine highly cost effective.
Global coverage with three doses of hepatitis B vaccine is estimated at 82 percent, and is as high as 92 percent in the Western Pacific. Despite improvements in global vaccine coverage in the past decade, disparities still result from competing health priorities, limited resources, poor health systems, inadequate monitoring and supervision, among other things. The delivery of hepatitis B vaccine to all newborns who need the vaccine and the HPV vaccine to protect women from cervical cancer are key steps in closing the preventable disease gap between the rich and the poor worldwide.
Photo by Alosh Bennett via Flckr
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