The Journal Clinical Infectious Diseases has a special supplement on challenge trials (human infection trials) of a Hep C vaccine (now that Hep C is a curable disease):
Volume 77, Issue Supplement_3, 15 August 2023
SUPPLEMENT ARTICLES
Controlled Human Infection Model for Hepatitis C Virus Vaccine Development: Is It Time to Be Real?
Hepatitis C virus (HCV) elimination has been a goal of the public health and scientific communities since its identification in 1989. Despite the advance and availability of highly effective antiviral regimens to treat HCV infection, it is unlikely that global HCV elimination can be achieved without an effective preventive vaccine. Because of the lack of appropriate animal models for preclinical testing and the perception that highly effective treatments would suffice in addressing the global burden of HCV, HCV vaccine development has not been a high priority. To accelerate vaccine development, the concept of a controlled human infection model (CHIM) for HCV has been proposed, in which healthy human volunteers would be deliberately infected with HCV for the purpose of testing the efficacy of candidate vaccines. This concept of challenge studies is not new and has been applied to more than 25 infectious agents, including the cholera vaccine, for which all efficacy data that served as the basis for regulatory approval were obtained from CHIM studies. Without a CHIM strategy, HCV vaccine development may not be feasible. In a recent phase 2 randomized controlled trial, over 900 people who inject drugs were screened to enroll 548 individuals to receive a T-cell–based HCV vaccine candidate or placebo. After a monumental effort that took over 6 years to complete, the trial documented 75 incident HCV infections overall, with only 45 included in the final analysis, and showed no protection against initial infection or progression to chronicity with the vaccine. While this study demonstrated that vaccine testing in the at-risk population can be done, future testing of additional HCV vaccine candidates using a similar pathway may be impractical in light of the duration and cost. With the ability to cure those who do not clear the virus, HCV CHIM is now a conceivable approach that could be a critically important, if not necessary, intermediate stage of vaccine development. HCV CHIM could de-risk vaccine candidates, accelerate development, reduce cost, and allow the selection of more promising candidates for further testing in larger clinical trials. CHIM may conceivably be used for larger phase 2/3 efficacy trials as a basis for clinical approval. In developing such a model, many challenges and questions must be addressed. In this Supplement issue, we, the editors of this Supplement commissioned various articles written by respective subject matter experts who provide their perspectives and opinions on these challenges and questions, ranging from the source of viral inoculum and the safety of transient HCV infection to the perspective of potential volunteers and the ethics of CHIM. While we strive to be data-driven and evidence-based, some of the opinions represent the views of the authors of each article and may be controversial. Ultimately, we hope these perspectives will enable fulsome discussion about the feasibility of HCV CHIM and lead to the development of well-designed clinical protocols.
Supplement sponsorship. This article appears as part of the supplement “Controlled Human Infection Model for HCV Vaccine Development,” sponsored by Toronto General Research Institute, United States National Institutes of Health, Johns Hopkins University, the Canadian Institutes of Health Research (CIHR), and the Canadian Network on Hepatitis C (CanHepC). CanHepC is funded by a joint initiative of CIHR (HPC-178912) and the Public Health Agency of Canada.
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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.
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- Supplementary data
Volunteering for Infection: Participant Perspectives on a Hepatitis C Virus Controlled Human Infection Model
The perspectives of former challenge study participants and a survey of other potential volunteers can inform the design of hepatitis C virus controlled human infection models, including on topics such as transparency, volunteer safety and risk, and compensation.
Ethical human subjects research requires participants to be treated safely and respectfully, yet much bioethical debate takes place without participants. We aim to address this gap in the context of controlled human infection model (CHIM) research. Based upon our own experience as study participants, and bolstered by a survey of 117 potential hepatitis C virus CHIM participants, we present ideas to inform efficient, ethical, and scientifically useful study design. We advocate for full protocol transparency, higher compensation, commitment to the rapid dissemination of study results, and proactive efforts to detail risk-minimization efforts as early as possible in the recruitment process, among other measures. We encourage researchers to proactively partner with volunteer advocacy organizations that promote collective representation of volunteers to maximize their agency, and guard against ethical issues arising from healthy human subjects research.
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- Supplementary data
First Do No Harm? Modeling Risks and Benefits of Challenge Trials for Hepatitis C Vaccine DevelopmentGet access
- Background
In 2019, about 58 million individuals were chronically infected with hepatitis C virus. Some experts have proposed challenge trials for hepatitis C virus vaccine development.
MethodsWe modeled incremental infections averted through a challenge approach, under varying assumptions regarding trial duration, number of candidates, and vaccine uptake. We computed the benefit-risk ratio of incremental benefits to risks for challenge versus traditional approaches. We also benchmarked against monetary costs of achieving incremental benefits through treatment.
ResultsOur base case assumes 3 vaccine candidates, each with an 11% chance of success, corresponding to a 30% probability of successfully developing a vaccine. Given this probability, and assuming a 5-year difference in duration between challenge and traditional trials, a challenge approach would avert an expected 185 000 incremental infections with 20% steady-state uptake compared to a traditional approach and 832 000 with 90% uptake (quality-adjusted life-year benefit-risk ratio, 72 000 & 323 000). It would cost at least $92 million and $416 million, respectively, to obtain equivalent benefits through treatment. BRRs vary considerably across scenarios, depending on input assumptions.
ConclusionsBenefits of a challenge approach increase with more vaccine candidates, faster challenge trials, and greater uptake.
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- Supplementary data
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- Earlier:
Monday, May 15, 2023
and here are my posts on challenge trials (and Covid vaccines).
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