Deliberate infection in research: ethical perspective of controlled human infection studies.

A controlled human infection study is the deliberate exposure of a healthy volunteer to an infectious pathogen under a strict controlled environment. Although there has been noticeable contribution of such studies to the biomedical research involving understanding of disease pathogen interaction, vaccine development, etc, they are in direct contradiction of core ethical principles such as non-maleficence. The major ethical dilemma lies in the deliberate exposure without certain direct benefits. This narrative review discusses the ethical challenges and need for robust ethical framework taking in account recent international guidelines, debates on trial design and placebo use, and evidence-based analyses of trial conduct and reporting. Analysis of ethical principles such as proportionality, respect for persons' decision, and social value has been done through this article with emphasis on challenge strain selection, participant selection, control group design and adverse event monitoring. Special attention was paid to CHIS in low-and middle-income countries, where potential direct benefits, and issues like justice and capacity building complicate standard ethical convention. We further examined the CHIS status in India despite its substantial infectious disease burden, placing this gap within the country's evolving ethical and regulatory landscape. We argue that CHIS can be morally acceptable with stringent context-sensitive ethical standards, and transparency in reporting, thereby prioritising public trust and equitable benefit sharing.