Herd immunity, vaccination and moral obligation.

The public health benefits of herd immunity are often used as the justification for coercive vaccine policies. Yet, 'herd immunity' as a term has multiple referents, which can result in ambiguity, including regarding its role in ethical arguments. The term 'herd immunity' can refer to (1) the herd immunity threshold, at which models predict the decline of an epidemic; (2) the percentage of a population with immunity, whether it exceeds a given threshold or not; and/or (3) the indirect benefit afforded by collective immunity to those who are less immune. Moreover, the accumulation of immune individuals in a population can lead to two different outcomes: elimination (for measles, smallpox, etc) or endemic equilibrium (for COVID-19, influenza, etc). We argue that the strength of a moral obligation for individuals to contribute to herd immunity through vaccination, and by extension the acceptability of coercion, will depend on how 'herd immunity' is interpreted as well as facts about a given disease or vaccine. Among other things, not all uses of 'herd immunity' are equally valid for all pathogens. The optimal conditions for herd immunity threshold effects, as illustrated by measles, notably do not apply to the many pathogens for which reinfections are ubiquitous (due to waning immunity and/or antigenic variation). For such pathogens, including SARS-CoV-2, mass vaccination can only be expected to delay rather than prevent new infections, in which case the obligation to contribute to herd immunity is much weaker, and coercive policies less justifiable.

COVID-19 vaccine boosters for young adults: a risk benefit assessment and ethical analysis of mandate policies at universities.

In 2022, students at North American universities with third-dose COVID-19 vaccine mandates risk disenrolment if unvaccinated. To assess the appropriateness of booster mandates in this age group, we combine empirical risk-benefit assessment and ethical analysis. To prevent one COVID-19 hospitalisation over a 6-month period, we estimate that 31 207-42 836 young adults aged 18-29 years must receive a third mRNA vaccine. Booster mandates in young adults are expected to cause a net harm: per COVID-19 hospitalisation prevented, we anticipate at least 18.5 serious adverse events from mRNA vaccines, including 1.5-4.6 booster-associated myopericarditis cases in males (typically requiring hospitalisation). We also anticipate 1430-4626 cases of grade ≥3 reactogenicity interfering with daily activities (although typically not requiring hospitalisation). University booster mandates are unethical because they: (1) are not based on an updated (Omicron era) stratified risk-benefit assessment for this age group; (2) may result in a net harm to healthy young adults; (3) are not proportionate: expected harms are not outweighed by public health benefits given modest and transient effectiveness of vaccines against transmission; (4) violate the reciprocity principle because serious vaccine-related harms are not reliably compensated due to gaps in vaccine injury schemes; and (5) may result in wider social harms. We consider counterarguments including efforts to increase safety on campus but find these are fraught with limitations and little scientific support. Finally, we discuss the policy relevance of our analysis for primary series COVID-19 vaccine mandates.

Public health ethics: critiques of the "new normal".

The global response to the recent coronavirus pandemic has revealed an ethical crisis in public health. This article analyses key pandemic public health policies in light of widely accepted ethical principles: the need for evidence, the least restrictive/harmful alternative, proportionality, equity, reciprocity, due legal process, and transparency. Many policies would be considered unacceptable according to pre-pandemic norms of public health ethics. There are thus significant opportunities to develop more ethical responses to future pandemics. This paper serves as the introduction to this Special Issue of Monash Bioethics Review and provides background for the other articles in this collection.

Moralization and Mismoralization in Public Health.

Moralization is a social-psychological process through which morally neutral issues take on moral significance. Often linked to health and disease, moralization may sometimes lead to good outcomes; yet moralization is often detrimental to individuals and to society as a whole. It is therefore important to be able to identify when moralization is inappropriate. In this paper, we offer a systematic normative approach to the evaluation of moralization. We introduce and develop the concept of 'mismoralization', which is when moralization is metaethically unjustified. In order to identify mismoralization, we argue that one must engage in metaethical analysis of moralization processes while paying close attention to the relevant facts. We briefly discuss one historical example (tuberculosis) and two contemporary cases related to COVID-19 (infection and vaccination status) that we contend to have been mismoralized in public health. We propose a remedy of de-moralization that begins by identifying mismoralization and that proceeds by neutralizing inapt moral content. De-moralization calls for epistemic and moral humility. It should lead us to pull away from our tendency to moralize-as individuals and as social groups-whenever and wherever moralization is unjustified.

The unintended consequences of COVID-19 vaccine policy: why mandates, passports and restrictions may cause more harm than good.

Vaccination policies have shifted dramatically during COVID-19 with the rapid emergence of population-wide vaccine mandates, domestic vaccine passports and differential restrictions based on vaccination status. While these policies have prompted ethical, scientific, practical, legal and political debate, there has been limited evaluation of their potential unintended consequences. Here, we outline a comprehensive set of hypotheses for why these policies may ultimately be counterproductive and harmful. Our framework considers four domains: (1) behavioural psychology, (2) politics and law, (3) socioeconomics, and (4) the integrity of science and public health. While current vaccines appear to have had a significant impact on decreasing COVID-19-related morbidity and mortality burdens, we argue that current mandatory vaccine policies are scientifically questionable and are likely to cause more societal harm than good. Restricting people's access to work, education, public transport and social life based on COVID-19 vaccination status impinges on human rights, promotes stigma and social polarisation, and adversely affects health and well-being. Current policies may lead to a widening of health and economic inequalities, detrimental long-term impacts on trust in government and scientific institutions, and reduce the uptake of future public health measures, including COVID-19 vaccines as well as routine immunisations. Mandating vaccination is one of the most powerful interventions in public health and should be used sparingly and carefully to uphold ethical norms and trust in institutions. We argue that current COVID-19 vaccine policies should be re-evaluated in light of the negative consequences that we outline. Leveraging empowering strategies based on trust and public consultation, and improving healthcare services and infrastructure, represent a more sustainable approach to optimising COVID-19 vaccination programmes and, more broadly, the health and well-being of the public.

Against COVID-19 vaccination of healthy children.

COVID-19 vaccination of children has begun in a number of countries with provisional regulatory approval and public support. This article provides an ethical analysis of COVID-19 vaccination of healthy children. Specifically, we present three of the strongest arguments that might justify COVID-19 vaccination of children: (a) an argument from paternalism, (b) an argument from indirect protection and altruism, and (c) an argument from global eradication. We offer a series of objections to each of these arguments to show that none of them is currently tenable. Given the minimal direct benefit of COVID-19 vaccination for healthy children, the potential for rare risks to outweigh these benefits and to undermine vaccine confidence, the substantial evidence that COVID-19 vaccination confers adequate protection to risk groups whether or not healthy children are vaccinated and that current vaccines do not provide sterilizing immunity, and given that eradication of the virus is neither feasible nor a high priority for global health, we argue that routine COVID-19 vaccination of healthy children is currently ethically unjustified. Since mandates for children have already been implemented in some places (e.g., California) and may be considered elsewhere, we also present two additional arguments explicitly against making COVID-19 vaccination mandatory for children.

Ethics review of COVID-19 human challenge studies: A joint HRA/WHO workshop.

This report of a joint World Health Organization (WHO) and United Kingdom (UK) Health Research Authority (HRA) workshop discusses the ethics review of the first COVID-19 human challenge studies, undertaken in the midst of the pandemic. It reviews the early efforts of international and national institutions to define the ethical standards required for COVID-19 human challenge studies and create the frameworks to ensure rigorous and timely review of these studies. This report evaluates the utility of the WHO's international guidance document Key criteria for the ethical acceptability of COVID-19 human challenge studies (WHO Key Criteria) as a practical resource for the ethics review of COVID-19 human challenge studies. It also assesses the UK HRA's approach to these complex ethics reviews, including the formation of a Specialist Ad-Hoc Research Ethics Committee (REC) for COVID-19 Human Challenge Studies to review all current and future COVID-19 human challenge studies. In addition, the report outlines the reflections of REC members and researchers regarding the ethics review process of the first COVID-19 human challenge studies. Finally, it considers the potential ongoing scientific justification for COVID-19 human challenge studies, particularly in relation to next-generation vaccines and optimisation of vaccination schedules. Overall, there was broad agreement that the WHO Key Criteria represented an international consensus document that played a powerful role in setting norms and delineating the necessary conditions for the ethical acceptability of COVID-19 human challenge studies. Workshop members suggested that the WHO Key Criteria could be practically implemented to support researchers and ethics reviewers, including in the training of ethics committee members. In future, a wider audience may be engaged by the original document and potential additional materials, informed by the experiences of those involved in the first COVID-19 human challenge studies outlined in this document.

Vaccine-enhanced disease: case studies and ethical implications for research and public health.

Vaccination is a cornerstone of global public health. Although licensed vaccines are generally extremely safe, both experimental and licensed vaccines are sometimes associated with rare serious adverse events. Vaccine-enhanced disease (VED) is a type of adverse event in which disease severity is increased when a person who has received the vaccine is later infected with the relevant pathogen. VED can occur during research with experimental vaccines and/or after vaccine licensure, sometimes months or years after a person receives a vaccine. Both research ethics and public health policy should therefore address the potential for disease enhancement. Significant VED has occurred in humans with vaccines for four pathogens: measles virus, respiratory syncytial virus, Staphylococcus aureus, and dengue virus; it has also occurred in veterinary research and in animal studies of human coronavirus vaccines. Some of the immunological mechanisms involved are now well-described, but VED overall remains difficult to predict with certainty, including during public health implementation of novel vaccines. This paper summarises the four known cases in humans and explores key ethical implications. Although rare, VED has important ethical implications because it can cause serious harm, including death, and such harms can undermine vaccine confidence more generally - leading to larger public health problems. The possibility of VED remains an important challenge for current and future vaccine development and deployment. We conclude this paper by summarising approaches to the reduction of risks and uncertainties related to VED, and the promotion of public trust in vaccines.

Imagination and remembrance: what role should historical epidemiology play in a world bewitched by mathematical modelling of COVID-19 and other epidemics?

Although every emerging infectious disease occurs in a unique context, the behaviour of previous pandemics offers an insight into the medium- and long-term outcomes of the current threat. Where an informative historical analogue exists, epidemiologists and policymakers should consider how the insights of the past can inform current forecasts and responses.

Viewpoint of a WHO Advisory Group Tasked to Consider Establishing a Closely-monitored Challenge Model of Coronavirus Disease 2019 (COVID-19) in Healthy Volunteers.

WHO convened an Advisory Group (AG) to consider the feasibility, potential value, and limitations of establishing a closely-monitored challenge model of experimental severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) in healthy adult volunteers. The AG included experts in design, establishment, and performance of challenges. This report summarizes issues that render a COVID-19 model daunting to establish (the potential of SARS-CoV-2 to cause severe/fatal illness, its high transmissibility, and lack of a "rescue treatment" to prevent progression from mild/moderate to severe clinical illness) and it proffers prudent strategies for stepwise model development, challenge virus selection, guidelines for manufacturing challenge doses, and ways to contain SARS-CoV-2 and prevent transmission to household/community contacts. A COVID-19 model could demonstrate protection against virus shedding and/or illness induced by prior SARS-CoV-2 challenge or vaccination. A limitation of the model is that vaccine efficacy in experimentally challenged healthy young adults cannot per se be extrapolated to predict efficacy in elderly/high-risk adults.

Prioritizing second-generation SARS-CoV-2 vaccines through low-dosage challenge studies.

The design of human challenge studies balances scientific validity, efficiency and study safety. This Perspective explores some advantages and disadvantages of 'low-dosage' challenge studies, in the setting of testing second-generation vaccines against COVID-19. Compared with a conventional vaccine challenge, a low-dosage vaccine challenge would be more likely to start, and start earlier. A low-dosage challenge would also be less likely to rule out a vaccine candidate that would have potentially been effective, particularly in certain target uses. A key ethical advantage of a low-dosage challenge over a conventional challenge is that both it and its dose escalation process are safer for each participant. Low-dosage studies would require larger numbers of participants than conventional challenges, but this and other potential disadvantages are less serious than they may initially appear. Overall, low-dosage challenges should be considered for certain roles such as prioritizing between second-generation vaccines against COVID-19.

Invisible epidemics: ethics and asymptomatic infection.

Interactions between microbes and human hosts can lead to a wide variety of possible outcomes including benefits to the host, asymptomatic infection, disease (which can be more or less severe), and/or death. Whether or not they themselves eventually develop disease, asymptomatic carriers can often transmit disease-causing pathogens to others. This phenomenon has a range of ethical implications for clinical medicine, public health, and infectious disease research. The implications of asymptomatic infection are especially significant in situations where, and/or to the extent that, the microbe in question is transmissible, potentially harmful, and/or untreatable. This article reviews the history and concept of asymptomatic infection, and relevant ethical issues associated with this phenomenon. It illustrates the role and ethical significance of asymptomatic infection in outbreaks, epidemics, and pandemics-including recent crises involving drug resistance, Zika, and Covid19. Serving as the Introduction to this Special Issue of Monash Bioethics Review, it also provides brief summaries of the other articles comprising this collection.

Key criteria for the ethical acceptability of COVID-19 human challenge studies: Report of a WHO Working Group.

This report of the WHO Working Group for Guidance on Human Challenge Studies in COVID-19 outlines ethical standards for COVID-19 challenge studies. It includes eight Key Criteria related to scientific justification, risk-benefit assessment, consultation and engagement, co-ordination of research, site selection, participant selection, expert review, and informed consent. The document aims to provide comprehensive guidance to scientists, research ethics committees, funders, policymakers, and regulators in deliberations regarding SARS-CoV-2 challenge studies by outlining criteria that would need to be satisfied in order for such studies to be ethically acceptable.

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 ethically, including by conducting challenge studies (also known as controlled human infection studies (CHIs)) with SARS-CoV-2 (the virus which causes COVID-19). Such research is controversial, with concerns being raised about the social, legal, ethical and clinical implications of infecting healthy volunteers with SARS-CoV-2 for research purposes. Systematic risk evaluations are critical to inform assessments of the ethics of any proposed SARS-CoV-2 CHIs. Such evaluations will necessarily take place within a rapidly changing and at times contested epidemiological landscape, in which differing criteria for the ethical acceptability of research risks have been proposed. This paper critically reviews two such criteria and evaluates whether the use of effective treatment should be a necessary condition for the ethical acceptability of SARS-CoV-2 CHIs, and whether the choice of study sites should be influenced by COVID-19 incidence levels. The paper concludes that ethical evaluations of proposed SARS-CoV-2 CHIs should be informed by rigorous, consultative and holistic approaches to systematic risk assessment.