The First- and Second-Order Ethical Reasons Approach: The Case of Human Challenge Trials

At the height of the Covid pandemic, there was much discussion in the literature about using human challenge trials (HCTs) to expedite the development of effective Covid-19 vaccines. Historically, reluctance to fully accept HCTs has largely been due to potential conflicts with the principle of nonmaleficence in bioethics. Only a few commentators have explored this topic in depth. In this paper, we claim that to address ethical concerns regarding HCTs, two types of ethical reasons should be identified and investigated: first-order reasons that can be given to claim that a practice in itself is in direct conflict with the principles of bioethics; and second-order reasons that take into consideration how a practice is carried out and its consequences. We argue that understanding these ethical reasons is crucial for guiding the implementation of HCTs. We investigate a first-order reason against HCTs when the practice is in conflict with the principle of nonmaleficence, and when it is not. Following this argument and assuming there is no first-order reason based on nonmaleficence that hinders using HCTs, we argue there may be second-order reasons to guide implementation of this practice, such as difficulty in obtaining informed consent; protection of the weaker party; and trust in the scientific enterprise.