Controlled Human Infection Studies Research Articles

Ethics & utility of controlled human infection studies (CHIS) in low- & middle-income countries

Ethics & utility of controlled human infection studies (CHIS) in low- & middle-income countries

Virtue ethics and the unsettled ethical questions in controlled human infection studies.

Controlled human infection studies (CHIs) involve the intentional infection of human subjects for a scientific aim. Though some past challenge trials have involved serious ethical abuses, in the last few decades, CHIs have had a strong track record of safety. Despite increased attention to the ethics of CHIs during the COVID-19 pandemic, CHIs remain controversial, and there has been no in-depth treatment of CHIs through the lens of virtue ethics. In this article, we argue that virtue theory can be helpful for addressing CHIs that present a constellation of controversial, unresolved, and/or under-regulated ethical issues. We begin with some brief background on virtue ethics. We then substantiate our claim that some CHIs raise a constellation of ethical issues that are unresolved in the ethics literature and/or lack adequate regulatory guidance by demonstrating that CHIs can present indeterminate social value, risks to third parties, limitations on the right to withdraw from research, and questions about the upper limit of allowable risk. We argue that the presence of a virtuous investigator, with virtues such as prudence, compassion, and integrity, is especially important when these unresolved research ethics issues arise, which is the case for certain types of controlled human infection studies. We use the historical example of Walter Reed and the Yellow Fever Commission to illustrate this claim, and we also highlight some contemporary examples. We end by sketching some practical implications of our view, such as ensuring that investigators with experience running CHIs are involved in novel CHI models.

Establishing a single-sex controlled human Schistosoma mansoni infection model for Uganda: protocol for safety and dose-finding trial.

Control of schistosomiasis depends on a single drug, praziquantel, with variable cure rates, high reinfection rates, and risk of drug resistance. A vaccine could transform schistosomiasis control. Preclinical data show that vaccine development is possible, but conventional vaccine efficacy trials require high incidence, long-term follow-up, and large sample size. Controlled human infection studies (CHI) can provide early efficacy data, allowing the selection of optimal candidates for further trials. A Schistosoma CHI has been established in the Netherlands but responses to infection and vaccines differ in target populations in endemic countries. We aim to develop a CHI for Schistosoma mansoni in Uganda to test candidate vaccines in an endemic setting. This is an open-label, dose-escalation trial in two populations: minimal, or intense, prior Schistosoma exposure. In each population, participants will be enrolled in sequential dose-escalating groups. Initially, three volunteers will be exposed to 10 cercariae. If all show infection, seven more will be exposed to the same dose. If not, three volunteers in subsequent groups will be exposed to higher doses (20 or 30 cercariae) following the same algorithm, until all 10 volunteers receiving a particular dose become infected, at which point the study will be stopped for that population. Volunteers will be followed weekly after infection until CAA positivity or to 12 weeks. Once positive, they will be treated with praziquantel and followed for one year. The trial registry number is ISRCTN14033813 and all approvals have been obtained. The trial will be subjected to monitoring, inspection, and/or audits.

COVID-19 controlled human infection studies: worries about local community impact and demands for local engagement

In spring, summer and autumn 2020, one abiding argument against controlled human infection (CHI) studies of SARS-CoV-2 vaccines has been their impact on local communities. Leading scientists and bioethicists expressed...

SARS-CoV-2 challenge studies: ethics and risk minimisation

COVID-19 poses an exceptional threat to global public health and well-being. Recognition of the need to develop effective vaccines at unprecedented speed has led to calls to accelerate research pathways...

Judging the social value of controlled human infection studies.

In controlled human infection (CHI) studies, investigators deliberately infect healthy individuals with pathogens in order to study mechanisms of disease or obtain preliminary efficacy data on investigational vaccines and medicines. CHI studies offer a fast and cost-effective way of generating new scientific insights, prioritizing investigational products for clinical testing, and reducing the risk that large numbers of people are exposed to ineffective or harmful substances in research or in practice. Yet depending on the pathogen, CHI studies can involve significant risks or burdens for participants, pose risks to individuals or communities not involved in the research, and lead to public controversy. It is therefore essential to ensure that the risks of CHI studies are justified by their social value-that is, their potential to generate benefits for society-and that public trust can be maintained. In this paper, we aim to clarify how research sponsors, research ethics committees and other reviewers should judge the social value of CHI studies. We develop a list of relevant considerations for making social value judgments based on the standard view of social value. We then use this list to discuss the example of potentially conducting dengue virus CHI studies in endemic settings. We argue that dengue virus CHI studies in endemic settings would fall on the higher end of the spectrum of social value, mostly because of their potential to redirect all fields of future dengue research. Drawing on this discussion, we derive several general recommendations for how reviewers should judge the social value of CHI studies.

Informed consent for controlled human infection studies in low- and middle-income countries: Ethical challenges and proposed solutions.

In controlled human infection studies (CHIs), participants are deliberately exposed to infectious agents in order to better understand the mechanism of infection or disease and test therapies or vaccines. While most CHIs have been conducted in high-income countries, CHIs have recently been expanding into low- and middle-income countries (LMICs). One potential ethical concern about this expansion is the challenge of obtaining the voluntary informed consent of participants, especially those who may not be literate or have limited education. In some CHIs in LMICs, researchers have attempted to address this potential concern by limiting access to literate or educated populations. In this paper, we argue that this practice is unjustified, as it does not increase the chances of obtaining valid informed consent and therefore unfairly excludes illiterate populations and populations with lower education. Instead, we recommend that investigators improve the informed consent process by drawing on existing data on obtaining informed consent in these populations and interventions aimed at improving their understanding. Based on a literature review, we provide concrete suggestions for how to follow this recommendation and ensure that populations with lower literacy or education are given a fair opportunity to protect their rights and interests in the informed consent process.

Selecting participants fairly for controlled human infection studies.

Controlled human infection (CHI) studies involve the deliberate exposure of healthy research participants to infectious agents to study early disease processes and evaluate interventions under controlled conditions with high efficiency. Although CHI studies expose participants to the risk of infection, they are designed to offer investigators unique advantages for studying the pathogenesis of infectious diseases and testing potential vaccines or treatments in humans. One of the central challenges facing investigators involves the fair selection of research subjects to participate in CHI studies. While there is widespread agreement that investigators have a duty to select research participants fairly, this principle also yields conflicting ethical imperatives, for example requiring investigators to both exclude potential participants with co-morbidities since they face increased risks, but also to include them in order to ensure generalizability. In this paper we defend an account of fair subject selection that is tailored to the context of CHI studies. We identify the considerations of fairness that bear directly on selecting participants for CHI studies and provide investigators and members of IRBs and RECs with a principled way to navigate the conflicting imperatives to which these considerations give rise.

The right to withdraw from controlled human infection studies: Justifications and avoidance.

The right to withdraw from research without penalty is well established around the world. However, it has been challenged in some corners of bioethics based on concerns about various harms-to participants, to scientific integrity, and to research bystanders-that may stem from withdrawal. These concerns have become particularly salient in emerging debates about the ethics of controlled human infection (CHI) studies in which participants are intentionally infected with pathogens, often in inpatient settings with extensive follow-up. In this article, I provide support for preserving the right to withdraw from research without penalty and demonstrate that it is also typically justified in the specific context of CHI studies. The right is well aligned with individual freedoms outside the research setting, where autonomous individuals are permitted to engage in behaviors that will foreseeably cause them harm; where they cannot be compelled to satisfy contracts for their services, nor penalized for failure to do so; and where their behavior is not constrained by public health authorities except in extreme circumstances. These freedoms are supported by U.S. law, as well as by ethical analysis that is more globally relevant. The problems associated with the right to withdraw, however, remain. The best approach to addressing them is not to restrict the right but rather to avoid initiating research when withdrawal would be especially problematic. If research proceeds, steps can still be taken to minimize participant withdrawal without infringing the right. Investigators can avoid participant surprise through informed consent focused on a study's most burdensome aspects and promote study completion through financial incentives. Should participants nonetheless seek to withdraw, investigators may attempt to persuade them not to do so by encouraging consideration of the range of potential harms that may result. Researchers conducting CHI studies and other research from which withdrawal might be especially problematic should prepare for the possibility of participant withdrawal, respect participant requests to withdraw without penalty, and incorporate various measures to avoid such requests.