Controlled Human Infection Studies - Pioneering Ethical Frontiers in Medical Research

Controlled Human Infection Studies – Pioneering Ethical Frontiers in Medical Research


The Bioethics Unit of the Indian Council of Medical Research (ICMR) has unveiled a visionary consensus policy statement on CHIS, sparking spirited discussions on the prospects and ethical implications of such studies within the scientific community.


GS-03 (Science and Technology)

GS-02 (Health)


Controlled Human Infection Studies (CHIS)

Mains Questions:

  • What are Controlled Human Infection Studies (CHIS) and how have they been historically utilized in medical research? (150 words)
  • What are the key ethical challenges associated with CHIS, and how can they be addressed? (150 words)

Dimensions of the Article:

  • The Historical Perspective of Controlled Human Infection Studies (CHIS)
  • The Role of CHIS in Vaccine Development
  • Ethical Challenges Surrounding CHIS

The Historical Perspective of Controlled Human Infection Studies (CHIS)

  • In the realm of medical research, Controlled Human Infection Studies, also known as human challenge studies, have been a significant tool for understanding infectious diseases.
  • One such landmark study dates back to the early 1900s, where a yellow fever study demonstrated the transmission of the virus through mosquitoes. Throughout history, researchers have employed less virulent strains of microbes to study diseases with established treatment options.
  • These studies, conducted on a limited number of healthy volunteers, aimed to gain insights into various aspects of infection and disease progression. Moreover, they have occasionally acted as catalysts in expediting the development of medical interventions.

The Role of CHIS in Vaccine Development

  • A vital application of human challenge studies is in the domain of vaccine development. However, it is crucial to note that CHIS should never serve as a replacement for phase-3 efficacy trials. Rather, they complement conventional phase-3 clinical trials by providing valuable information about candidate vaccines’ safety and immune responses.
  • Subsequently, phase-3 trials following CHIS often require fewer volunteers, streamlining the overall development process. For instance, in recent decades, CHIS studies have played a significant role in accelerating vaccine development against diseases such as typhoid and cholera.
  • Even during the COVID-19 pandemic, CHIS was leveraged at the Imperial College London, with 36 volunteers, to study facets of the SARS-CoV-2 infection. The World Health Organization (WHO) itself recognized the potential of CHIS in expediting COVID-19 vaccine development, further validating its importance.

Ethical Challenges Surrounding CHIS

  • While CHIS holds immense promise in advancing medical research, it is essential to acknowledge the ethical challenges that accompany this approach. Robust and well-trained systems are vital for ensuring the ethical conduct of these studies.
  • Collaborations with reputable institutions and experienced scientists become imperative in navigating the complex ethical minefield. Past experiences, such as the HPV vaccine trial in Andhra Pradesh, have underscored the need for stringent oversight to avoid ethical violations.
  • The magnitude of ethical challenges during CHIS is considerably higher, amplifying the risk of potential misuse. Monetary dimensions may tempt unscrupulous actors, necessitating a cautious approach in managing volunteer involvement. To mitigate such risks, any implementation of CHIS in India should strictly adhere to studying diseases with established safe and effective treatment.

Way Forward:

Gradual Implementation of CHIS for Novel Microbes/Diseases

  • While the potential of CHIS in understanding novel diseases is undeniable, a prudent approach dictates that India should exercise caution in its implementation. It is crucial for Indian scientists to attain expertise in this domain before embarking on CHIS endeavors for diseases with limited medical intervention.
  • This prudent waiting period allows for the establishment of robust institutional structures and mechanisms to uphold ethical standards and safeguard the well-being of volunteers.

Emphasizing Collaborations and Knowledge Exchange

  • India’s journey towards embracing CHIS should be complemented by fostering collaborations with international institutions and scientists who possess invaluable experience in conducting controlled human infection studies.
  • Knowledge exchange and learning from established experts will pave the way for India to create a strong foundation for ethically sound and scientifically rigorous CHIS practices.


Controlled Human Infection Studies (CHIS) represent a significant advancement in medical research, promising to unravel critical insights into infectious diseases and bolster vaccine development. However, as India contemplates embarking on this frontier, it must tread cautiously, prioritizing robust institutional mechanisms and stringent ethical oversight. Collaborations and knowledge exchange with reputable institutions and experts will enhance India’s capabilities in this field. With steadfast commitment to ethical practices and patient safety, India can stride confidently towards a future where CHIS plays a pivotal role in advancing public health and medical interventions