Ethical and Practical Issues Associated With the Possibility of Using Controlled Human Infection Trials in Developing a Hepatitis C Virus Vaccine

Ethical Requirements for Human Challenge Studies: A Systematic Review of Reasons

Human challenge studies (HCS) are controlled clinical trials in which participants are deliberately infected with a pathogen. Such trials are being developed for an increasing number of diseases. Partly as a result of the coronavirus disease 2019 (COVID-19) pandemic, there has been a recent ethical debate about the reasons for and against HCS in general, or rather, about the requirements that individual HCS must fulfill to be ethically acceptable. A systematic review was conducted to categorize and summarize such requirements and the reasons given for them. Ethics literature was searched in PubMed, Google Scholar, BELIT, and PhilPapers; eligibility criteria were articles published in a scientific/scholarly journal (original research, reviews, editorials, opinion pieces, and conference/meeting reports). Of 1,322 records identified, 161 publications were included, with 183 requirements (with associated reasons) in 10 thematic categories extracted via qualitative content analysis. In synthesizing and interpreting the requirements and their reasons, three issues emerge as particularly sensitive in the case of HCS: the meaning of the right to withdraw from research procedures, communication of researchers with the public and various stakeholders, and the conditions of informed consent. However, four other issues, not specific to HCS, stand out as the most controversial: the acceptable level of risk to participants, payment of participants, protection of vulnerable groups, and standards for international collaborations. Controversies in these areas indicate that further debate is warranted, possibly leading to more specific instructions in ethics guidance documents.

Controlled Human Infection Model for Hepatitis C Virus Vaccine Development: Trial Design Considerations

The design of a clinical trial for a controlled human infection model (CHIM) to accelerate hepatitis C virus (HCV) vaccine development requires careful consideration. The design of a potential approach to HCV CHIM is outlined, involving initial sentinel cohorts to establish the safety and curability of the viral inoculum followed by larger cohorts to establish the spontaneous clearance rate for each inoculum. The primary endpoint would be HCV clearance by 24 weeks post-inoculation, recognizing that the prevention of chronic infection would be the primary goal of HCV vaccine candidates. Additional considerations are discussed, including the populations to be enrolled, the required monitoring approach, indications for antiviral therapy, and the required sample size for different CHIM approaches. Finally, safety considerations for CHIM participants are discussed.

Ethics of Controlled Human Infection Studies With Hepatitis C Virus

Global elimination of hepatitis C virus (HCV) will be difficult to attain without an effective HCV vaccine. Controlled human infection (CHI) studies with HCV were not considered until recently, when highly effective treatment became available. However, now that successful treatment of a deliberate HCV infection is feasible, it is imperative to evaluate the ethics of establishing a program of HCV CHI research. Here, we evaluate the ethics of studies to develop an HCV CHI model in light of 10 ethical considerations: sufficient social value, reasonable risk-benefit profile, suitable site selection, fair participant selection, robust informed consent, proportionate compensation or payment, context-specific stakeholder engagement, fair and open collaboration, independent review and oversight, and integrated ethics research. We conclude that it can be ethically acceptable to develop an HCV CHI model. Indeed, when done appropriately, developing a model should be a priority on the path toward global elimination of HCV.

To Include or Occlude: Rational Engineering of HCV Vaccines for Humoral Immunity

Direct-acting antiviral agents have proven highly effective at treating existing hepatitis C infections but despite their availability most countries will not reach the World Health Organization targets for elimination of HCV by 2030. A prophylactic vaccine remains a high priority. Whilst early vaccines focused largely on generating T cell immunity, attention is now aimed at vaccines that generate humoral immunity, either alone or in combination with T cell-based vaccines. High-resolution structures of hepatitis C viral glycoproteins and their interaction with monoclonal antibodies isolated from both cleared and chronically infected people, together with advances in vaccine technologies, provide new avenues for vaccine development.