GS 3 –Science and Technology
Covid-19 is currently killing thousands of people a day. The vast majority of the world’s population has no acquired immunity to the disease. And the economy is grinding to a halt to curb its spread. Given the dire situation, the value of even marginally speeding the widespread availability of a vaccine is incredibly high and warrants much more attention and more extreme measures.
Meaning of Human Challenge Trials
Human challenge trials are trials in which participants are intentionally challenged (whether or not they have been vaccinated) with an infectious disease organism. This challenge organism may be close to wild-type and pathogenic, adapted and/or attenuated from wild-type with less or no pathogenicity, or genetically modified in some manner.
Infectious human challenge studies involve deliberate exposure of human volunteers to infectious agents. Human challenge studies have been conducted over hundreds of years and have contributed vital scientific knowledge that has led to advances in the development of drugs and vaccines. Nevertheless, such research can appear to be in conflict with the guiding principle in medicine to do no harm. Well documented historical examples of human exposure studies would be considered unethical by current standards. It is essential that challenge studies be conducted within an ethical framework in which truly informed consent is given.
Human Challenge Trials and Coronavirus
As laboratories around the world race to develop a vaccine for the novel coronavirus, many people have volunteered to take part in a controversial testing method called human challenge trials. As of April 27, a global initiative called 1DaySooner had registered 3,817 people in 52 countries who had signed up for such trials. The method, which involves intentionally infecting volunteers with the novel coronavirus, is being promoted in order to “speed up” the process of preparing a vaccine.
Under human challenge trials, participants of both the vaccine group and placebo group upon consent are deliberately exposed to the infection – thus are “challenged” by the disease organism. Proponents of the method believe that such trials could save valuable time in developing a Covid-19 vaccine, as researchers would not have to wait for participants to contract the infection under real-world conditions.
A paper released on March 31 in The Journal of Infectious Diseases by researchers Nir Eyal, Marc Lipsitch, and Peter G Smith has proposed replacing Phase 3 with human challenge trials. The paper said, “Controlled human challenge trials of SARS-CoV-2 vaccine candidates could accelerate the testing and potential rollout of efficacious vaccines. By replacing conventional Phase 3 testing of vaccine candidates, such trials may subtract many months from the licensure process, making efficacious vaccines available more quickly.”
How are new vaccines developed?
Following pre-clinical research, the vaccine is tested in a very small group of people – sometimes as few as half a dozen – in what is called a ‘Phase I’ clinical study. This helps to rule out major safety problems and also helps doctors to work out the right dose for the next step in the testing process.
Phase II trials involve giving the vaccine to a larger number of people (often 100 or 200 but sometimes in the 1,000s). At this point, researchers want to see whether the vaccine gives a consistent immune response and they watch for any side effects that might occur.
Where a disease is reasonably common, phase III trials can be conducted to test how the vaccine protects against natural infection. These studies often include tens of thousands of healthy volunteers so that doctors have a better chance of discovering rare problems which did not show up in smaller Phase II studies and prove that the vaccine prevents the disease.
It doesn’t end there. After a vaccine is approved by regulators it can be made available to the public – either via funded national immunisation programmes or to purchase privately. At this point, ongoing monitoring of the vaccine’s effect takes place as part of what can be called Phase IV trials and doctors are encouraged report any unexpected apparent side-effects.
The ethical imperative
Supporters of these types of experiments — called human challenge trials or controlled human infection models — argue that they are the quickest and cheapest way to develop new vaccines, test medicines and study the basic progression of some of humanity’s most enduring infectious foes, as well as some new ones. The strategy is popular with organizations such as the British biomedical charity the Wellcome Trust and the Bill & Melinda Gates Foundation, as they spend their billions trying to tackle neglected ailments of the developing world. Malaria, dengue fever, cholera, influenza, typhoid and tuberculosis — which among them kill some three million people each year — are all being investigated by scientists who make healthy people purposely sick.
Still, ethicists say it’s time for a more detailed assessment of the rights and wrongs of human challenge trials. That’s because, although the vast majority have taken place in rich nations, scientists increasingly seek volunteers in places where the diseases being studied are endemic. The shift is important if treatments and vaccines are to work, proponents of these studies say, because people who live under constant threat of a disease often develop a different immunological response.
The volunteers — and sometimes those around them — are required to take on a known risk without the promise of any direct benefit to themselves in return. That’s very different, say, from people who already have cancer or are infected with HIV signing up for an experimental medicine. It’s why human challenge trials tend to focus on conditions with acute (that is, immediate) symptoms that can be treated and cleared up with no lasting damage. Ethical review committees charged with assessing and approving these projects have given most the green light.
Previous Year Questions