Are human challenge studies effective?

Subject: Science and Technology

Section: Biotechnology

Context:

On July 17, the ICMR Bioethics Unit posted the consensus policy statement for the ethical conduct of controlled human infection studies (CHIS), also known as human challenge studies, in India.

Why is India venturing into undertaking human challenge studies?

Human challenge studies, in which human beings are exposed to diseases to learn more about it, have been carried out for hundreds of years.
Human challenge studies are almost always conducted to understand the various facets of infectious microbes and the diseases or conditions caused by such pathogens.
Example: The yellow fever study in the early 1900s established that mosquitoes transmitted the yellow fever virus.
However, India has not undertaken such trials before and will be collaborating with scientists and institutions outside India who have been conducting such studies.
The disease burden and mortality from infectious diseases is significantly high at around 30% in India.
The inclusion of human challenge studies will:
- Speed up the process of finding safe and effective interventions in the form of drugs and/or vaccines.
- Help in providing better insight into multiple aspects of even well-studied pathogens, infection, transmission, disease pathogenesis and prevention.
Many countries, including low-and middle-income countries such as Colombia, Kenya, Tanzania and Thailand, have carried out human challenge studies.

What is the fundamental difference between human clinical trials and human challenge studies?

Sr.No.	Human Challenge Studies	Human Clinical Trials
1.	Participants are strongly advised to adopt and adhere to safety measures to avoid getting infected and any exposure to the microbes and infection arising in the participants from such an exposure is left to chance.	Volunteers are deliberately exposed to disease-causing pathogens.
2.	Undertaken to study the safety and efficacy of drugs and vaccines	Carried out to understand the various facets of infection and disease pathogenesis besides selecting the best candidate drug or vaccine.
3.	Adverse effects of the candidate drugs or vaccines are not known	Though adverse effects of the candidate drugs or vaccines are not known, volunteers face an additional risk when deliberately exposed to the pathogen
4.	Undertaken to study all kinds of diseases.	Often undertaken to study “less deadly diseases” such as influenza, dengue, typhoid, cholera and malaria

What special safeguards are followed to reduce harm to participants?

The infectious agents that are tested in human challenge studies are well-known and studied.
To reduce harm to the participants, a weaker or less virulent form of the pathogen is used.
The other important requirement is the availability of a ‘rescue remedy’ to prevent the disease from progressing to its severe form.

What makes human challenge studies ethically more challenging vis-à-vis traditional clinical trials?

That participants in a human challenge trial are deliberately exposed to a disease-causing pathogen.
As per the ICMR statement:
- Only healthy individuals in the 18-45 years age bracket are to be enrolled.
- Children and women who are pregnant, lactating or planning to conceive within the study period will not be enrolled.
- Participants with pre-existing medical conditions are to be excluded.

Know more about CHIS: https://optimizeias.com/icmr-argues-for-controlled-human-infection-studies/