Human Challenge Studies  

 Human Challenge Studies  

This article covers “Daily Current Affairs” and the topic details “Human Challenge Studies”. The topic “Human Challenge Studies” has relevance in the “Science and Technology” section of the UPSC CSE exam.

For Prelims:

What are Human Challenge Studies? 

How are they different from Clinical Trials?

For Mains:

GS3:  Science and Technology. Awareness in Biotechnology

Why in the news?

The consensus policy statement for the ethical conduct of controlled human infection studies (CHIS) in India was posted by the ICMR Bioethics Unit recently.


Human Challenge Studies 

  • The World Health Organization (WHO) defines human challenge studies as intentional trials where participants, whether vaccinated or not, are deliberately exposed to an infectious disease organism. 
  • This practice, which dates back centuries, has been instrumental in advancing medical science. 
  • In fact, the first authentic human challenge study was carried out in the 1700s to evaluate the efficacy of variolation, an inoculation method, in preventing smallpox.
  • In modern times, these studies have significantly contributed to the development of vaccines for various diseases, such as cholera, typhoid fever, influenza, and dengue fever.


Significance of Human Challenge Studies 

While real-world studies are crucial for medical research, human challenge studies offer certain advantages that are not easily attainable through conventional research methods. Here are some key points regarding the significance of human challenge studies:

  • Understanding infection dynamics: Human challenge studies help researchers determine the minimum amount of virus required to initiate an infection, which can be challenging to ascertain in real-world scenarios.
  • Observing infection progression: These studies allow scientists to closely observe the entire process of infection from the moment the virus enters the body, providing detailed information on how the virus interacts with the immune system.
  • Transmission dynamics: Scientists can learn how an individual infected with a virus like SARS-CoV-2 transmits viral particles into the environment, aiding in the understanding of transmission dynamics.
  • Identifying symptomatic and asymptomatic individuals: Human challenge studies can help identify which individuals are more likely to develop symptoms and those who may remain asymptomatic after infection.
  • Efficacy of vaccines: Researchers can use human challenge studies to assess the efficacy of potential vaccines, especially for second- and third-generation vaccines. With numerous vaccine candidates, these studies can prioritize the most promising candidates for further testing and prove their effectiveness, especially in areas with low transmission rates.
  • Insights into immunological response: By observing the immune responses of participants, researchers can gain a better understanding of the type of immune response required to protect individuals from reinfection.


Difference between human clinical trials and human challenge studies

Special safeguards 

  • In human challenge studies, the tested infectious agents are usually well-known and studied, except for rare cases like SARS-CoV-2 causing COVID-19.
  • To minimize harm, a less virulent form of the pathogen is used.
  • A crucial requirement is having a ‘rescue remedy’ available to prevent severe disease progression.
  • In studies involving SARS-CoV-2, remdesivir was used as a rescue remedy, despite not knowing its substantial mortality benefit.


Ethical Challenges 

  • Deliberate Exposure to Disease-Causing Pathogen: The intentional exposure of participants to disease-causing pathogens raises ethical concerns due to potential risks and harm involved.
  • Exclusion Criteria and Medical Examination: Determining eligibility and excluding individuals with pre-existing medical conditions necessitates detailed medical examination to ensure participant safety.
  • Payment for Participation: The issue of payment for participation must be handled carefully to avoid undue inducement and exploitation of volunteers.
  • Informed Consent: Ensuring truly informed consent becomes challenging, especially when studying specific age groups or disadvantaged populations.
  • Availability of Rescue Remedy: The need for an effective rescue remedy becomes crucial, as disease outcomes in individuals cannot be entirely predicted even with less infectious agents.
  • Historical Violations: Previous trials have witnessed violations of informed consent requirements, highlighting the importance of maintaining ethical standards in human challenge studies.


More about the news: 

According to the ICMR consensus statement–

  • Only healthy individuals aged 18-45 years will be enrolled in the study.
  • Pregnant, lactating women, and those planning to conceive during the study period will not be enrolled; however, children will be included when deemed appropriate.
  • The consent form will include information about payment for participation, but the exact amount will only be disclosed to volunteers after they have given their consent to participate.

Human challenge studies have played a significant role in advancing medical science by providing unique insights into infectious diseases and vaccine development. While these studies offer valuable benefits, they also pose ethical challenges that require careful consideration and adherence to stringent safeguards to ensure participant safety and uphold ethical standards in research. The ICMR’s consensus statement outlines specific criteria and guidelines to address these concerns and promote responsible and informed conduct of controlled human infection studies in India.


Explained | Are human challenge studies effective? – The Hindu 

plutus ias current affairs eng med 4th August 2023

Q1. With reference to Human challenge studies, consider the following statements: 

  1. Human challenge studies involve intentionally exposing participants to infectious disease organisms.
  2. The first human challenge study evaluated the efficacy of vaccination against Coronavirus. 
  3. Traditional clinical trials directly assess the transmission dynamics of infectious diseases. 

Which of the statements given above is/are NOT correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 3 only 

(d) None 

Answer: (b) 


Q2. Consider the following:

  1. Human challenge studies are a new approach in medical science.
  2. Human challenge studies can help identify individuals who may remain asymptomatic after infection.
  3. Human challenge studies prioritise less deadly diseases such as influenza, dengue, typhoid, cholera, and malaria.

How many of the abovementioned statement/s is/are correct ?

(a) Only one 

(b) Only two 

(c) All three 

(d) None

Answer: (b)

Q3. Discuss the significance of human challenge studies in advancing medical science and vaccine development. Also, cite key differences between human challenge studies and traditional clinical trials.

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