A recent news report in Science aims to lay out the facts surrounding human challenge studies in which diseases are given to healthy people as a means of improving drug and vaccine development.


Scientists have long been infecting healthy people with disease-causing organisms as a way to study how they work, how to treat them, and how to prevent infection altogether. This practice dates back to the 1700s when Edward Jenner discovered that exposing people to the harmless Cowpox virus could prevent them from acquiring Smallpox, a far more dangerous disease. This discovery eventually led to the eradication of Smallpox.

Although these types of trials, known today as human challenge studies, have led to great discoveries, darker events blemish their history. In particular, such experimentation was conducted by the Nazi’s on unwilling prisoners in the concentration camps. Following World War II, the occurrence of these atrocities led officials to form the Nuremberg Code, a set of research ethics principles that states all participants in human studies must give informed consent, participate voluntarily, and be free to quit the study at any time. Although these stipulations were created in the mid-1900s, involuntary experimentation on humans occurred in American prisons well into the 1970s.

Today, the regulations surrounding human challenge studies are strict and place volunteer safety at the forefront. Any researcher hoping to conduct one of these studies in the United States must gain approval not only from the Food and Drug Administration (FDA) but also from the ethics board of the institution in which they plan to conduct their research. This approval is stringent and includes numerous stipulations. Before gaining permission, investigators must consider numerous factors such as how they will screen people to ensure it is safe for them to participate and how they will prevent volunteers from spreading the infection. All of the variables in question must be assessed on a disease by disease basis as safety precautions will be greatly different for the virus causing the flu than they will be for the parasite that causes malaria. For example, when working with the influenza virus, it is administered such that it will only cause infection of the upper airways and will spare the lungs. This prevents development of pneumonia, a disease far more dangerous than the flu. Furthermore, for some infections, such as Dengue fever, it is possible to use a weakened version of the disease such that less severe symptoms will result.

Typically, human challenge studies are done to determine the effectiveness of drug treatments or vaccines against certain infectious organisms. In fact, later this year, the FDA will review a vaccine that has been created by a researcher named Myron Levine at the U.S. National Institute of Allergy and Infectious Diseases (NIAID) in Maryland. Human challenge studies were conducted to develop this vaccine which prevents Cholera, a disease transmitted through contaminated food and water. Cholera leads to severe diarrhea which can very rapidly progress to fatal dehydration. This vaccine could be a particularly valuable tool in preventing this disease.

Levine, who has spent much of his career working in human challenge studies, states that when considering whether to conduct a study he asks himself, “would I want my kids, siblings, or spouse to participate? If the answer is ‘no,’ we don’t do it.” Of course, the risks of conducting human challenge studies are undeniable but so are their benefits. Normally, development of pharmaceuticals is an extremely slow and expensive process. Human challenge studies can both speed up identification of potentially effective vaccines and treatments, as well as cut down on the cost needed to decide which options to abandon and which to pursue.

In his recent news report in Science, Jon Cohen does not attempt to hide that there are risks associated with giving diseases to healthy people. He does, however, provide a compelling argument that with stringent safety procedures, the benefits of human challenge studies are unquestionable.




Written By: Katrina Cristall, BSc (Hons)

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