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.

Human infection challenge studies have been proposed as a means to accelerate SARS-CoV2 vaccine development and thereby help to mitigate a prolonged global public health crisis. A key criterion for the ethical acceptability of SARS-CoV2 HCS is that potential benefits outweigh risks. Although the assessment of risks and benefits is meant to be a standard part of research ethics review, systematic comparisons are particularly important in the context of SARS-CoV2 HCS in light of the significant potential benefits and harms at (...) stake as well as the need to preserve public trust in research and vaccines. In this paper we explore several considerations that should inform systematic assessment of SARS-CoV-2 HCS. First, we detail key potential benefits of SARS-CoV-2 HCS including, but not limited to, those related to the acceleration of vaccine development. Second, we identify where modelling is needed to inform risk-benefit assessments. Modelling will be particularly useful in comparing potential benefits and risks of HCS with those of vaccine field trials under different epidemiological conditions and estimating marginal risks to HCS participants in light of the background probabilities of infection in their local community. We highlight interactions between public health policy and research priorities, including situations in which research ethics assessments may need to strike a balance between competing considerations. (shrink)

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. (shrink)

Antibiotic allergies are commonly reported among patients, but most do not experience reactions on rechallenge with the same agents. These reported allergies complicate management of infections in patients labelled as having penicillin allergy, including serious infections where penicillin-based antibiotics are the first-line (most effective and least toxic) treatment option. Allergy labels are rarely questioned in clinical practice, with many clinicians opting for inferior second-line antibiotics to avoid a perceived risk of allergy. Reported allergies thereby can have significant impacts on patients (...) and public health, and present major ethical challenges. Antibiotic allergy testing has been described as a strategy to circumvent this dilemma, but it carries limitations that often make it less feasible in patients with acute infections or in community settings that lack access to allergy testing. This article provides an empirically informed ethical analysis of key considerations in this clinical dilemma, using _Staphylococcus aureus_ bacteraemia in patients with penicillin allergies as a case study. We argue that prescribing first-line penicillin-based antibiotics to patients with reported allergies may often present a more favourable ratio of benefits to risks, and may therefore be more ethically appropriate than using second-line drugs. We recommend changes to policy-making, clinical research and medical education, in order to promote more ethically acceptable responses to antibiotic allergies than the status quo. (shrink)