The Ethics of Intentionally Infecting Humans in Research

Abstract: In controlled human infection (CHI) research, researchers intentionally expose people to pathogens to gain scientific insights. CHI research has led to many scientific breakthroughs. The proposed use of CHI research to accelerate vaccine development during the COVID-19 pandemic captured public imagination and the attention of ethicists, with more papers written on CHI research ethics than ever before. The controversy about CHI research ethics continues, with disagreement among ethicists on a few key issues. Perhaps most fundamentally, ethicists debate whether this research is ethically unique.

In this presentation, based on a book that is forthcoming with Oxford University Press, I argue that a lack of understanding of this research contributes to this ongoing ethical controversy. Few have appreciated the need to distinguish between the ethics of creating a new disease model for the first time versus using a model proven to be effective and safe in a CHI study to test interventions—a distinction that can do important ethical work and help calibrate the level of ethical scrutiny required. While CHI models uniquely raise several unresolved ethical issues at once, requiring additional scrutiny, CHI studies involve less ethical complexity and can undergo standard review.

I will describe and analyze past uses of CHI research (including during the COVID-19 pandemic), provide an ethical framework that distinguishes models from studies, highlight ethically sound and promising future uses of CHI research emerging from this analysis, and finally discuss implications of this analysis for research ethics more generally.

Keywords: Controlled Human Infection Research, Challenge studies, Research ethics