Exploring Risks of Human Challenge Trials For COVID-19

Assessing the risks of current COVID-19 challenge trials systematically

A large international collaboration has started a series of SARS-CoV-2 (COVID) human challenge trials (HCTs). However, critics of previously proposed COVID HCTs deemed them unethical for posing excessive risks to participants. These concerns raise the need to evaluate the risks of the planned COVID HCTs. Systematic analysis reveals that, although the risks of these trials would be high in some populations, they are clearly acceptable for eligible individuals and may even qualify as "minimal" for them. This conclusion is important for evaluating the planned COVID HCTs and highlights the importance of assessing the risks of later COVID HCTs and HCTs in future pandemics systematically.

Research ethics and public trust in vaccines: the case of COVID-19 challenge trials

Despite their clearly demonstrated safety and effectiveness, approved vaccines against COVID-19 are commonly mistrusted. Nations should find and implement effective ways to boost vaccine confidence. But the implications for ethical vaccine development are less straightforward than some have assumed. Opponents of COVID-19 vaccine challenge trials, in particular, made speculative or empirically implausible warnings on this matter, some of which, if applied consistently, would have ruled out most COVID-19 vaccine trials and many non-pharmaceutical responses.

The Case for Human Challenge Trials in COVID-19

The COVID-19 pandemic has necessitated rapid research to aid in the understanding of the disease and the development of novel therapeutics. One option is to conduct controlled human infection trials (CHITs). In this article I examine the history of deliberate human infection and CHITs and their utilization prior to the COVID-19 pandemic, key ethical considerations of CHITs in the COVID-19 setting, an analysis of the World Health Organization's (WHO) Key criteria for the ethical acceptability of COVID-19 human challenge studies, and a review of the two COVID-19 CHITs that have already commenced, their compliance with the WHO criteria and other ethical considerations.

Exploring the ethics of tuberculosis human challenge models

We extend recent conversation about the ethics of human challenge trials to tuberculosis (TB). TB challenge studies could accelerate vaccine development, but ethical concerns regarding risks to trial participants and third parties have been a limiting factor. We analyse the expected social value and risks of different challenge models, concluding that if a TB challenge trial has between a 10% and a 50% chance of leading to the authorisation and near-universal delivery of a more effective vaccine 3-5 years earlier, then the trial would save between 26 400 and 1 100 000 lives over the next 10 years. We also identify five important ethical considerations that differentiate TB from recent human challenge trials: an exceptionally high disease burden with no highly effective vaccine; heightened third party risk following the trial, and, partly for that reason, uniquely stringent biosafety requirements for the trial; risks associated with best available TB treatments; and difficulties with TB disease detection. We argue that there is good reason to consider conducting challenge trials with attenuated strains like Bacillus Calmette-Guérin or attenuated Mycobacterium tuberculosis.

A template for the authoring of statistical analysis plans

A number of principal investigators may have limited access to biostatisticians, a lack of biostatistical training, or no requirement to complete a timely statistical analysis plan (SAP). SAPs completed early will identify design or implementation weak points, improve protocols, remove the temptation for p-hacking, and enable proper peer review by stakeholders considering funding the trial. An SAP completed at the same time as the study protocol might be the only comprehensive method for at once optimizing sample size, identifying bias, and applying rigor to study design. This ordered corpus of SAP sections with detailed definitions and a variety of examples represents an omnibus of best practice methods offered by biostatistical practitioners inside and outside of industry. The article presents a protocol template for clinical research design, enabling statisticians, from beginners to advanced.

SARS-CoV-2 entry into and evolution within a skilled nursing facility

SARS-CoV-2 belongs to the family Coronaviridae which includes multiple human pathogens that have an outsized impact on aging populations. As a novel human pathogen, SARS-CoV-2 is undergoing continuous adaptation to this new host species and there is evidence of this throughout the scientific and public literature. However, most investigations of SARS-CoV-2 evolution have focused on large-scale collections of data across diverse populations and/or living environments. Here we investigate SARS-CoV-2 evolution in epidemiologically linked individuals within a single outbreak at a skilled nursing facility beginning with initial introduction of the pathogen. The data demonstrate that SARS-CoV-2 was introduced to the facility multiple times without establishing an interfacility transmission chain, followed by a single introduction that infected many individuals within a week. This large-scale introduction by a single genotype then persisted in the facility. SARS-CoV-2 sequences were investigated at both the consensus and intra-host variation levels. Understanding the variability in SARS-CoV-2 during transmission chains will assist in understanding the spread of this disease and can ultimately inform best practices for mitigation strategies.

Ethical considerations of the vaccine development process and vaccination: a scoping review

BACKGROUND

Various vaccines have been developed and distributed worldwide to control and cope with COVID-19 disease. To ensure vaccines benefit the global community, the ethical principles of beneficence, justice, non-maleficence, and autonomy should be examined and adhered to in the process of development, distribution, and implementation. This study, therefore, aimed to examine ethical considerations of vaccine development and vaccination processes.

METHODS

A scoping review of the literature was conducted based on the Arkesy and O'Malley protocol to identify eligible studies published until November 2021. We searched Web of Science, PubMed, Scopus, and SciELO databases. The search was conducted using combinations of Medical Subject Heading (MeSH) search terms and keywords for Ethics, COVID-19, and vaccines in abstract, keywords, and title fields to retrieve potentially relevant publications. We included any study that reported one of the four principles of medical ethics: autonomy, justice, non-maleficence, and beneficence in the COVID-19 vaccine development and distribution and implementation of vaccinations. Letters, notes, protocols, and brief communications were excluded. In addition, we searched gray literature to include relevant studies (ProQuest database, conferences, and reports). Data were analyzed using framework analysis.

RESULTS

In total, 43 studies were included. Ethical considerations concluded two themes: (1) production and (2) distribution and vaccination. The production process consisted of 16 codes and 4 main Categories, distribution and vaccination process consisted of 12 codes and 4 main Categories. Moreover, the ethical considerations of special groups were divided into four main groups: health care workers (HCWs) (five codes), children and adolescents (five codes), the elderly (one code), and ethnic and racial minorities (three codes).

CONCLUSION

Due to the externalities of pandemics and the public and social benefits and harms of vaccination, it is not feasible to adhere to all four principles of medical ethics simultaneously and perfectly. This issue confronts individuals and policymakers with several moral dilemmas. It seems that decision-making based on the balance between social benefit and social harm is a better criterion in this regard, and the final decision should be made based on maximizing the public benefit and minimizing the public harm.

Do coronavirus vaccine challenge trials have a distinctive generalisability problem?

Notwithstanding the success of conventional field trials for vaccines against COVID-19, human challenge trials (HCTs) that could obtain more information about these and about other vaccines and further strategies against it are about to start in the UK. One critique of COVID-19 HCTs is their distinct paucity of information on crucial population groups. For safety reasons, these HCTs will exclude candidate participants of advanced age or with comorbidities that worsen COVID-19, yet a vaccine should (perhaps especially) protect such populations. We turn this cliché on its head. The truth is that either an HCT or a field trial has intrinsic generalisability limitations, that an HCT can expedite protection of high-risk participants even without challenging them with the virus, and that an important route to obtaining results generalisable to high-risk groups under either strategy is facilitated by HCTs.

A new day for human challenge trials?

Two years into the coronavirus disease 2019 (COVID-19) pandemic and following several hot debates, the world's first COVID-19 human challenge trial has recently been published by Killingley et al. We review its findings and explain why this particular juncture in time makes additional challenge trials for COVID-19 and for other diseases justified and important.

Testing fractional doses of COVID-19 vaccines

Switching to fractional doses could dramatically accelerate vaccination, and clinical evidence suggests that fractional doses of COVID-19 vaccines could be highly effective. However, there is uncertainty about the effectiveness of fractional doses. In this paper, we present the existing evidence and use epidemiological models to quantify benefits under various scenarios. We argue for more experimental or observational data to be collected urgently. Because switching to fractional dosing could dramatically accelerate vaccination, the potential benefits of further testing of fractional doses far outweigh the costs.

Due to the enormous economic, health, and social costs of the COVID-19 pandemic, there are high expected social returns to investing in parallel in multiple approaches to accelerating vaccination. We argue there are high expected social returns to investigating the scope for lowering the dosage of some COVID-19 vaccines. While existing evidence is not dispositive, available clinical data on the immunogenicity of lower doses combined with evidence of a high correlation between neutralizing antibody response and vaccine efficacy suggests that half or even quarter doses of some vaccines could generate high levels of protection, particularly against severe disease and death, while potentially expanding supply by 450 million to 1.55 billion doses per month, based on supply projections for 2021. An epidemiological model suggests that, even if fractional doses are less effective than standard doses, vaccinating more people faster could substantially reduce total infections and deaths. The costs of further testing alternative doses are much lower than the expected public health and economic benefits. However, commercial incentives to generate evidence on fractional dosing are weak, suggesting that testing may not occur without public investment. Governments could support either experimental or observational evaluations of fractional dosing, for either primary or booster shots. Discussions with researchers and government officials in multiple countries where vaccines are scarce suggests strong interest in these approaches.

An ongoing science-society-ethics experiment: The human challenge trial debate in COVID-19 pandemic: The human challenge trial debate in COVID-19 pandemic

Human challenge trials to deliberately infect volunteers with SARS-CoV-2 should inspire wider debates about research ethics and participants' motivations to take part in such studies.

The Ethics of Human Challenge Trials Using Emerging SARS-CoV-2 Virus Variants

The world's first COVID-19 human challenge trial using the D614G strain of SARS-CoV-2 is underway in the United Kingdom. The Wellcome Trust is funding challenge stock preparation of the Beta and Delta variant for a follow-up human challenge trial, and researchers at hVIVO are considering conducting these trials. However, little has been written thus far about the ethical justifiability of human challenge trials with SARS-CoV-2 variants of concern. We explore two specific characteristics of some variants that may initially be thought to make such trials unethical and conclude that SARS-CoV-2 variant challenge trials can remain ethical.

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 concern about undue usage of local residents' direly needed scarce resources at a time of great need and even about their unintended infection. They recommended either avoiding CHI trials or engaging local communities before conducting any CHIs. Similar recommendations were not made for the alternative-standard phase III field trials of these same vaccines. We argue that the health effects of CHI studies on local residents not participating in the study tend to be smaller and more positive than those of field trials. That is all the more so now that tested vaccines are being rolled out. Whether or not local community engagement is necessary for urgent vaccine studies in the pandemic, the case for its engagement is stronger prior to field trials than prior to CHI studies.