COVID-19 Human Challenge Studies: Ethical Issues and Controversies

Human challenge studies, also known as controlled human infection trials, involve the deliberate exposure of healthy volunteers to a pathogen under controlled conditions. During the COVID-19 pandemic, these studies became a focal point of ethical debate because they offered a path to faster vaccine and treatment development but required healthy people to accept infection risks. This article examines the ethical arguments for and against COVID-19 human challenge studies, the criteria used to judge their acceptability, and a practical framework for evaluating whether a proposed challenge study meets ethical standards. The content is intended for students, researchers, life-science professionals, and informed general readers who need to understand the ethical landscape instead of simply take a position.

The Purpose and History of Human Challenge Studies

Controlled human infection studies have a long history in biomedical research. They involve deliberately exposing a healthy volunteer to an infectious pathogen in a strictly controlled environment. These studies have contributed to understanding disease pathogen interactions and vaccine development, yet they stand in direct tension with core ethical principles such as non-maleficence, because researchers intentionally cause infection in people who may receive no direct medical benefit. The major ethical dilemma lies in this deliberate exposure without certain direct benefits to the participant.

The COVID-19 pandemic created a new and distinctive focus on human challenge studies. The first such trial was authorized in England in February 2021. Even after vaccines became available, multiple gaps remained in knowledge about treatment and prevention of the infection, and the global scale of morbidity and mortality created powerful incentives for accelerating medical knowledge through unorthodox methods. These incentives had to be balanced against ethical and pragmatic considerations, particularly given the limited state of knowledge about the diverse and longer term risks from contracting COVID-19. Considerable care was needed in assessing whether human challenge trials were appropriate for testing treatments or prevention measures.

The pandemic context matters for understanding why challenge studies were proposed at all. The Global Burden of Disease Study 2021 provided demographic estimates for 204 countries and territories and 811 subnational locations from 1950 to 2021, with particular emphasis on changes in mortality and life expectancy during the 2020 to 2021 COVID-19 pandemic period. The study drew on 22,223 data sources from vital registration, sample registration, surveys, censuses, and other sources to estimate mortality, with a subset used exclusively to estimate excess mortality due to the pandemic. This scale of health impact explains why researchers and policymakers considered challenge trials as a tool for faster answers.

Core Ethical Principles in Challenge Study Evaluation

The ethical evaluation of human challenge studies rests on several foundational principles that apply to all human subjects research but take on special weight when researchers deliberately cause infection.

Non-Maleficence and Deliberate Harm

The principle of non-maleficence requires researchers to avoid causing harm to participants. In a challenge study, the researcher intentionally administers a pathogen to a healthy person. This action creates harm risk that would not otherwise exist for that individual. The ethical question is whether this deliberate exposure can ever be justified when the participant receives no certain direct benefit. The justification must rest on the social value of the research, the proportionality of risks to potential benefits, and the quality of the informed consent process.

Respect for Persons and Autonomy

Respect for persons requires that individuals be treated as autonomous agents capable of making their own decisions. In challenge studies, this means participants must understand that they are being infected on purpose, that the risks are not fully known, and that they can withdraw at any time. The consent process must address the specific nature of challenge studies, including the fact that infection is certain instead of possible, and that the long term consequences of infection may be unknown.

Social Value and Proportionality

A study that exposes healthy people to infection must have sufficient social value to justify the risks. During the COVID-19 pandemic, the potential value included faster vaccine efficacy testing, better understanding of infection dynamics, and development of treatments. The proportionality principle requires that the expected benefits to society and to future patients outweigh the risks to participants. This calculation is difficult when the risks of COVID-19 itself were still emerging and not fully characterized.

Justice and Participant Selection

Justice requires that the burdens and benefits of research be distributed fairly. Challenge studies typically enroll healthy young adults because they face the lowest risk of severe outcomes. This creates a justice concern: the people who bear the risks of research may not be the people who benefit most from the results. The question of who should be asked to accept infection risks, and whether payment or other incentives distort voluntary participation, is central to the ethics of challenge studies.

The World Health Organization Criteria for Ethical Acceptability

The World Health Organization developed key criteria for the ethical acceptability of COVID-19 human challenge studies. These criteria provide a structured way to evaluate whether a proposed study meets ethical standards. An analysis of these criteria, along with a review of the two COVID-19 challenge trials that commenced, examined their compliance with the WHO criteria and other ethical considerations.

The WHO criteria address several domains that any research ethics committee should assess before approving a challenge study. These include the scientific justification for the study, the risk minimization plan, the participant selection process, the informed consent procedures, and the provisions for monitoring and compensation. The criteria also require that the study have a clear path to producing socially valuable results that could not be obtained through less risky methods.

For a decision framework, the WHO criteria can be operationalized as a set of questions that a research ethics committee or an independent reviewer should ask about any proposed COVID-19 challenge study. These questions form the basis of the assessment framework presented later in this article.

Risk Assessment and Quantification in COVID-19 Challenge Trials

One of the central ethical challenges for COVID-19 challenge studies was the unclear and developing risk profile of the virus. Researchers developed an interactive model for exploring the risks of a SARS-CoV-2 dosing study, which is a prerequisite for any challenge trial. The risk estimates were based on a Bayesian evidence synthesis model that could incorporate new data on infection fatality risks and infer rates of hospitalization.

The model estimated individual risk and extrapolated to overall mortality and hospitalization risk in a dosing study. For someone between 20 and 30 years of age, the infection fatality risk was estimated at 15.1 per 100,000, with a 95% uncertainty interval from 11.8 to 19.2. The risk of hospitalization was estimated at 130 per 100,000, with an interval from 100 to 160. These baseline risks could be reduced in a challenge trial through screening for comorbidities, selecting a lower risk population, and providing treatment. With stronger assumptions about these risk reductions, the projected fatality risk was as low as 2.5 per 100,000, with an interval from 1.6 to 3.9, and the hospitalization risk was projected at 22.0 per 100,000, with an interval from 14.0 to 33.7.

These estimates have direct implications for study design. A 50 person dosing trial was projected to have a 99.74% chance of no fatalities, with an interval from 99.8% to 99.9%, and a 98.9% probability of no cases requiring hospitalization, with an interval from 98.3% to 99.3%. These numbers illustrate why some researchers considered challenge trials ethically acceptable for low risk populations, while others remained concerned about the uncertainty intervals and the possibility of rare but severe outcomes.

At a Glance: Risk Estimates for a COVID-19 Dosing Study

The uncertainty intervals matter for ethical decision making. Even with screening and treatment, the upper bound of the fatality risk estimate was 3.9 per 100,000, meaning that a larger trial could still result in a death. The ethical acceptability of accepting this risk depends on the social value of the research, the quality of the consent process, and the availability of treatment.

Arguments For COVID-19 Human Challenge Studies

Acceleration of Vaccine and Treatment Development

The primary argument for COVID-19 challenge studies was speed. Traditional vaccine efficacy trials require waiting for participants to become naturally infected, which can take months and depends on community transmission levels. Challenge studies can provide efficacy data in weeks because every participant is exposed to the virus. During a pandemic with high global morbidity and mortality, this acceleration could save lives by getting effective vaccines and treatments to market sooner.

Addressing Knowledge Gaps

Even after vaccines became available, significant gaps remained in understanding COVID-19. These included questions about immune correlates of protection, the duration of immunity, the effectiveness of treatments at different stages of infection, and the reasons for varied disease severity. Challenge studies offered a controlled way to answer these questions because researchers could observe infection from the moment of exposure and collect samples at predetermined time points.

Controlled Conditions and Data Quality

Challenge studies allow for precise measurement of the infectious dose, the timing of exposure, and the subsequent course of infection. This level of control is impossible in natural infection studies where the timing and dose of exposure are unknown. The data quality from challenge studies can inform vaccine development, therapeutic testing, and public health policy with a precision that observational studies cannot match.

Risk Minimization Through Selection and Care

Proponents argued that the risks to challenge study participants could be minimized through careful screening. By excluding people with comorbidities, selecting young healthy adults, and providing close medical monitoring and treatment, the fatality and hospitalization risks could be reduced substantially below population baseline rates. The risk model projections supported this view, showing that screening and treatment could reduce fatality risk by roughly sixfold and hospitalization risk by roughly sixfold.

Arguments Against COVID-19 Human Challenge Studies

Uncertainty About Long Term Risks

The most significant argument against COVID-19 challenge studies was the limited knowledge about the diverse and longer term risks from contracting the virus. Early in the pandemic, it was not known which patients would develop prolonged symptoms, organ damage, or other sequelae. A challenge study participant who recovered from acute infection might still face unknown long term health consequences. The ethical principle of non-maleficence requires that researchers not expose participants to risks they cannot characterize or quantify.

Absence of Direct Benefit to Participants

Challenge study participants receive no certain direct medical benefit. They are infected with a virus that could make them ill, and the knowledge gained benefits society instead of the individual participant. This arrangement tests the limits of altruistic participation in research. While participants may receive payment or compensation, the question of whether such incentives constitute undue influence is a persistent ethical concern.

Justice Concerns in Participant Recruitment

Challenge studies typically recruit young, healthy, and often economically disadvantaged volunteers. The people who bear the risks of infection may be those with fewer alternatives for income or those who feel social pressure to contribute to pandemic response. This raises questions about whether participation is truly voluntary and whether the distribution of research burdens is fair.

Alternative Research Methods

Critics argued that challenge studies were not necessary because alternative methods could provide the needed data. These alternatives included traditional efficacy trials, human genetics studies, and careful observational research. The question was whether the acceleration provided by challenge studies justified the additional risks to participants, particularly when the incremental benefit over alternative methods was uncertain.

Community and Public Trust

Controlled human infection studies raise significant ethical, social, environmental, and logistical concerns beyond the individual participant. In settings where individuals are economically disadvantaged and may have limited access to healthcare, education, and basic social amenities, community engagement becomes a central element in ensuring ethical conduct and protection of participants rights. Research stakeholders in Uganda emphasized that meaningful community engagement should be a continuous process grounded in respect, justice, and partnership, instead of a procedural or regulatory obligation. The acceptability and success of challenge studies in low resource settings depends largely on effective intentional community engagement throughout the research process.

Informed Consent in Challenge Studies

What Participants Must Understand

Informed consent for a challenge study requires that participants understand several specific elements. They must know that they will be deliberately infected with a live pathogen. They must understand that the risks of infection are not fully known, particularly for long term outcomes. They must be informed about the screening process, the monitoring they will receive, and the treatments available if they become ill. They must also understand that they can withdraw from the study at any time.

The Problem of Therapeutic Misconception

Therapeutic misconception occurs when research participants believe that the study procedures are designed for their personal benefit instead of for the generation of generalizable knowledge. In challenge studies, this misconception could lead participants to underestimate the risks or overestimate the personal benefits of participation. Researchers have an obligation to ensure that participants understand the difference between research and clinical care.

Payment and Undue Influence

The question of payment for challenge study participation is ethically complex. Payment can acknowledge the time, inconvenience, and risk that participants assume. However, large payments to economically disadvantaged individuals could constitute undue influence, undermining the voluntariness of consent. Research ethics committees must assess whether the payment amount is appropriate and whether it distorts the participant's risk assessment.

Consent Capacity and Comprehension

Challenge studies require participants to understand complex probabilistic information about risks. Research ethics committees must verify that the consent process includes adequate comprehension checks and that participants have sufficient time to consider their decision. The consent process may need to include multiple sessions, written materials, and opportunities to ask questions.

Research Ethics Committee Perspectives

Research ethics committee members have specific perspectives on human challenge studies for COVID-19 vaccine development. A mixed methods study examined these perspectives, highlighting the considerations that committees apply when reviewing challenge study protocols. Ethics committees must balance the potential social value of the research against the risks to participants, and they must verify that the consent process is adequate for the specific risks involved.

Ethics committee members face a difficult task in evaluating challenge studies because the risk data are often incomplete and evolving. They must make judgments about acceptable risk levels, the adequacy of screening and monitoring plans, and the quality of the consent process. These judgments require expertise in infectious disease, research ethics, and risk communication.

The perspectives of ethics committee members are particularly important because these committees serve as the institutional gatekeepers for human subjects research. Their decisions determine whether challenge studies proceed, and their criteria for approval shape the design of future studies.

Legal and Regulatory Considerations

Human challenge trials raise distinctive legal and regulatory issues for COVID-19 research. The first such trial was authorized in England in February 2021, setting a precedent for regulatory approval of challenge studies during a pandemic. The legal framework for challenge studies must address liability for harm, compensation for research related injuries, and the authority of regulators to approve deliberate infection of healthy volunteers.

The ethical principles applicable to challenge studies must be balanced against the powerful incentives for unorthodox acceleration of medical knowledge. Given the limited state of knowledge about the diverse and longer term risks from COVID-19, considerable care needs to be devoted to any assessment of the appropriateness of human challenge trials. This care extends to the legal framework, which must protect participants while allowing valuable research to proceed.

Regulatory approval of a challenge study requires evidence that the study meets ethical and scientific standards. This includes evidence about the challenge strain, the infectious dose, the expected attack rate, and the availability of effective treatment for participants who become ill. Regulators must also consider whether the study population is appropriate and whether the consent process is adequate.

Decision Framework for Evaluating Ethical Acceptability

The following framework translates the ethical principles and WHO criteria into a practical assessment tool. It is designed for research ethics committee members, researchers, and others who must evaluate whether a proposed COVID-19 challenge study meets ethical standards.

Step 1: Assess Scientific Justification

The first question is whether the study has clear scientific value that cannot be achieved through less risky methods. The reviewer should ask what specific knowledge gap the study addresses, why a challenge study is necessary instead of an observational study or traditional trial, and how the results will be used to improve prevention or treatment.

Step 2: Evaluate the Risk Minimization Plan

The reviewer must assess whether the study design minimizes risks to participants. This includes the selection of a low risk challenge strain, the determination of an appropriate infectious dose, the screening criteria for excluding high risk participants, and the monitoring and treatment plan for participants who become infected.

Step 3: Examine Participant Selection and Recruitment

The reviewer must evaluate who will be recruited, how they will be recruited, and whether the recruitment process avoids coercion or undue influence. The participant population should be selected to minimize risk while allowing the study to answer its scientific questions.

Step 4: Review the Informed Consent Process

The consent process must be evaluated for its adequacy in communicating the specific risks of challenge participation. The reviewer should ask whether participants will understand that infection is deliberate, that long term risks are unknown, and that they can withdraw at any time.

Step 5: Verify Provisions for Monitoring and Compensation

The study must include adequate provisions for monitoring participants during and after the study, providing treatment for research related illness, and compensating participants for research related injuries. The reviewer must verify that these provisions are specified in the protocol and that resources are available to implement them.

Step 6: Consider Community Engagement

For studies conducted in low resource settings, the reviewer must assess whether the study includes adequate community engagement. This engagement should be continuous, grounded in respect and partnership, and designed to ensure that the community understands the study and supports its conduct.

Step 7: Document the Assessment

The reviewer should document the assessment of each criterion and the overall judgment about ethical acceptability. This documentation should include the reasons for the decision and any conditions attached to approval.

Records and Measurements for Ethical Oversight

Ethical oversight of challenge studies requires systematic record keeping and measurement. The following records should be maintained for any approved challenge study.

Protocol and Amendments

The approved protocol and all amendments should be maintained with version control. This record documents the scientific rationale, the risk minimization plan, and any changes made during the study.

Consent Documentation

Signed consent forms and consent process notes should be maintained for each participant. This record verifies that informed consent was obtained and documents what information was provided.

Screening and Eligibility Records

Screening assessments and eligibility determinations should be documented for each potential participant. This record verifies that exclusion criteria were applied consistently and that high risk individuals were not enrolled.

Adverse Event Reports

All adverse events, including serious adverse events, should be documented with dates, severity, and outcomes. This record is essential for monitoring the safety of participants and for determining whether the study should be modified or stopped.

Ethics Committee Minutes

Minutes of ethics committee meetings should document the review process, the questions raised, and the decisions made. This record provides accountability for the ethical oversight of the study.

Community Engagement Records

For studies involving community engagement, records should document the engagement activities, the community input received, and how that input influenced the study design or conduct.

Common Failure Patterns in Challenge Study Ethics

Several recurring problems can undermine the ethical acceptability of challenge studies. Recognizing these patterns is important for reviewers and researchers.

Inadequate Risk Characterization

A study may proceed without adequate data on the risks of the challenge strain or the study procedures. This failure is particularly concerning when long term risks are unknown, as was the case early in the COVID-19 pandemic.

Insufficient Screening

A study may enroll participants who are at higher risk than intended because the screening criteria are too broad or the screening procedures are not followed consistently. This failure increases the risk of severe outcomes among participants.

Inadequate Consent Process

A study may use a consent process that does not adequately communicate the specific risks of challenge participation. This failure can occur when the consent form is too complex, the comprehension check is insufficient, or participants are given insufficient time to decide.

Coercive Recruitment

A study may recruit participants in ways that are coercive or involve undue influence. This failure can occur when payment is too high, when recruitment targets economically disadvantaged populations, or when social pressure is applied to potential participants.

Inadequate Monitoring and Treatment

A study may not have adequate provisions for monitoring participants after infection or for providing treatment if participants become seriously ill. This failure can result in harm that could have been prevented with better planning.

Poor Community Engagement

A study conducted in a low resource setting may proceed without adequate community engagement, undermining trust and potentially exposing participants to risks they do not fully understand. This failure is particularly problematic when the community has limited access to healthcare and education.

Limitations of the Evidence Base

The ethical evaluation of COVID-19 challenge studies is limited by several factors that should be acknowledged.

Evolving Risk Data

The risk estimates for COVID-19 challenge studies were based on data that evolved rapidly during the pandemic. The Bayesian model was designed to incorporate new data as it became available, but the uncertainty intervals remained wide for some outcomes. Ethical judgments made early in the pandemic were based on less complete data than would be ideal.

Limited Experience with COVID-19 Challenge Studies

Only two COVID-19 challenge trials had commenced as of the 2024 analysis. This limited experience means that the ethical and practical challenges of conducting these studies are not fully understood. The compliance of these trials with the WHO criteria provides some evidence, but the sample size is small.

Generalizability of Risk Estimates

The risk estimates from the Bayesian model were based on specific assumptions about the challenge strain, the infectious dose, and the study population. These estimates may not generalize to other challenge strains, doses, or populations. The ethical evaluation of any specific study must consider the particular characteristics of that study.

Contextual Variation in Ethical Standards

Ethical standards for challenge studies vary across settings. Studies conducted in low and middle income countries raise additional considerations related to justice, capacity building, and community engagement. The ethical framework that applies in one setting may not apply in another.

Welfare and Safety Context

The welfare and safety of challenge study participants is the central ethical concern. The following considerations are essential for protecting participants.

Participant Monitoring

Challenge study participants should be monitored closely from the time of exposure through the resolution of infection and for a period afterward to detect any longer term effects. The monitoring plan should specify the frequency of assessments, the tests to be performed, and the criteria for hospital admission.

Treatment Availability

The study must have a plan for treating participants who become seriously ill. This plan should specify the treatments available, the criteria for initiating treatment, and the arrangements for hospital care if needed.

Withdrawal Procedures

Participants must be able to withdraw from the study at any time. The withdrawal procedures should specify how the participant will be monitored and treated after withdrawal, and how their data will be handled.

Long Term Follow Up

Given the unknown long term risks of COVID-19, challenge study participants should be offered long term follow up to detect any sequelae of infection. The follow up plan should specify the duration and the assessments to be performed.

Escalation Criteria

The study should have predefined criteria for escalating care or stopping the study if unexpected safety concerns arise. These criteria should be specified in the protocol and agreed upon by the ethics committee and the data safety monitoring board.

Professional Escalation Criteria

Researchers, ethics committee members, and clinicians involved in challenge studies should know when to escalate concerns to higher authorities. The following situations warrant escalation.

Unexpected Serious Adverse Events

Any serious adverse event that is unexpected or more severe than anticipated should be reported immediately to the ethics committee, the data safety monitoring board, and the regulatory authority.

Protocol Violations

Any violation of the approved protocol, particularly violations related to screening, consent, or monitoring, should be reported to the ethics committee and the study sponsor.

Concerns About Participant Safety

Any concern about participant safety that cannot be resolved at the study level should be escalated to the ethics committee and the regulatory authority.

Community Concerns

Any significant community concern about the study should be escalated to the study sponsor and the relevant authorities. Community concerns that are not addressed can undermine the acceptability of the study and the trust in the research enterprise.

Requests for Guidance

Researchers or ethics committee members who are uncertain about the ethical acceptability of a specific study feature should seek guidance from institutional ethics resources or professional bodies before proceeding.

Frequently Asked Questions

What is a human challenge study?

A human challenge study, also called a controlled human infection study, is a research design in which healthy volunteers are deliberately exposed to an infectious pathogen under controlled conditions. The purpose is to study the infection, test vaccines or treatments, or understand the disease process. These studies differ from traditional trials because infection is certain instead of possible, and participants receive no certain direct medical benefit.

Why were human challenge studies proposed for COVID-19?

Human challenge studies were proposed for COVID-19 because they could provide efficacy data for vaccines and treatments faster than traditional trials. In a challenge study, every participant is exposed to the virus, so researchers do not have to wait for natural infections to occur in the community. During a pandemic with high global morbidity and mortality, this acceleration was considered potentially valuable.

What are the main ethical concerns with COVID-19 challenge studies?

The main ethical concerns are the deliberate exposure of healthy people to a virus with unknown long term risks, the absence of direct benefit to participants, the potential for undue influence in recruitment, and the justice question of who bears the risks of research. The principle of non-maleficence is in direct tension with the deliberate infection of healthy volunteers.

How were risks estimated for COVID-19 challenge studies?

Researchers developed a Bayesian evidence synthesis model to estimate infection fatality risks and hospitalization risks for potential challenge study participants. For someone between 20 and 30 years of age, the baseline infection fatality risk was estimated at 15.1 per 100,000, and the hospitalization risk at 130 per 100,000. With screening and treatment, these risks could be reduced substantially.

What criteria did the World Health Organization establish for COVID-19 challenge studies?

The World Health Organization established key criteria for the ethical acceptability of COVID-19 human challenge studies. These criteria address scientific justification, risk minimization, participant selection, informed consent, and provisions for monitoring and compensation. An analysis of the two COVID-19 challenge trials that commenced examined their compliance with these criteria.

What is the role of research ethics committees in challenge studies?

Research ethics committees review challenge study protocols to assess whether they meet ethical standards. Committee members evaluate the scientific justification, the risk minimization plan, the consent process, and the provisions for participant protection. Their perspectives are important because they serve as the institutional gatekeepers for human subjects research.

How does informed consent work in a challenge study?

Informed consent in a challenge study requires that participants understand they will be deliberately infected, that the risks are not fully known, that they will receive monitoring and treatment, and that they can withdraw at any time. The consent process must address the specific nature of challenge studies and include comprehension checks to verify understanding.

What is the role of community engagement in challenge studies?

Community engagement is essential for the ethical conduct of challenge studies, particularly in low resource settings. Research stakeholders in Uganda emphasized that meaningful community engagement should be a continuous process grounded in respect, justice, and partnership. The acceptability and success of challenge studies depends on effective intentional community engagement throughout the research process.

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References and Further Reading

• Research Data Framework. National Institute of Standards and Technology.
• EQUATOR Network. EQUATOR Network.
• Experimental Design Assistant. NC3Rs.
• NCBI Literature Resources. National Center for Biotechnology Information.
• PubMed. National Library of Medicine.
• COVID-19 and the ethics of human challenge trials.. Medicine, health care, and philosophy, 2021.
• The Case for Human Challenge Trials in COVID-19.. Journal of bioethical inquiry, 2024.
• Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950-2021, and the impact of the COVID-19 pandemic: a comprehensive demographic analysis for the Global Burden of Disease Study 2021.. Lancet (London, England), 2024.
• Exploring Risks of Human Challenge Trials For COVID-19.. Risk analysis : an official publication of the Society for Risk Analysis, 2021.
• Human Challenge Trials: Ethical and Legal Issues for COVID-19 Research.. Journal of law and medicine, 2021.
• Burden of 375 diseases and injuries, risk-attributable burden of 88 risk factors, and healthy life expectancy in 204 countries and territories, including 660 subnational locations, 1990-2023: a systematic analysis for the Global Burden of Disease Study 2023.. Lancet (London, England), 2025.
• Evolving ethics of COVID-19 challenge trials.. The Lancet. Infectious diseases, 2021.
• Global, regional, and national trends in routine childhood vaccination coverage from 1980 to 2023 with forecasts to 2030: a systematic analysis for the Global Burden of Disease Study 2023.. Lancet (London, England), 2025.
• Deliberate infection in research: ethical perspective of controlled human infection studies.. 2026.
• "… Infections are not confined in labs…": Community engagement for Controlled Human Infection Studies: Opinions of researchers, bioethicists and research regulators in Uganda.. 2026.
• Ethical challenges to patient autonomy in the era of artificial intelligence: a systematic review.. 2026.
• One Health ethics in context: Justice, interdependence, and normative pluralism.. 2026.
• Human Challenge Trials: Ethical and Legal Issues for COVID-19 Research. Journal of Law and Medicine, 2021.
• Perspectives of research ethics committee members on human challenge studies in the development of vaccines against COVID-19: A mixed methods study. Annals of Palliative Medicine, 2021.

This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.