Gimme a Boost?


Kyle Ferguson, PhD and Arthur Caplan, PhD

Publish date

Tag(s): Legacy post
Topic(s): Vaccines

Kyle Ferguson, PhD Arthur Caplan, PhD

The unfairness of “boosters” might seem self-evident: Millions of Americans are receiving third doses of COVID-19 vaccines before billions in poorer countries receive their firsts. Global vaccine distribution is starkly unequal, and now Americans are getting even more of a precious resource. The severe disparities in vaccine access and coverage around the world lead some people to feel that rich countries’ “booster” campaigns are unethical. But that feeling, no matter how good-natured and sincere, is mistaken. Enhanced vaccination campaigns are ethically justified despite the context of global inequality in which they occur. To think otherwise is to be in the grips of a flawed framing of the issue, one that creates a false ethical dilemma.

In the wake of the Delta variant’s surge and with immunity appearing to wane in American vaccinees, the CDC in October recommended that millions of Americans receive additional doses of COVID-19 vaccines. Even more recently, with Omicron infections on the rise and another dark winter on the horizon, the CDC broadened its recommendation to all adults. The US joins a growing list of high-income countries (HICs) who have enhanced their COVID-19 vaccination campaigns by providing additional doses to their citizens and residents.  

However, critics maintain that moral failure is underway. HICs’ enhanced vaccination campaigns are rolling out despite protests by some world leaders, public health officials, and scholars. In August, the WHO called for a temporary moratorium on administering “booster” shots, arguing that doses were more urgently needed in low- and middle-income countries (LMICs). Similarly, Krause and colleagues argued that “booster” campaigns are politically driven and that HICs ought to allocate doses outside their borders.

Critics frame the issue as an ethical dilemma: Either HICs can allocate doses towards domestic “booster” campaigns; or, HICs can allocate those doses to LMICs. Thus framed, the moral question HICs must ask is: Shall we use these doses as boosters at home, or shall we vaccinate the world? 

We believe that HICs’ enhanced vaccination campaigns are ethically justified and that critics’ arguments don’t work for three reasons. First, the term “booster” is mistaken from the scientific point of view and misleading from the moral point of view. Second, the moral assumptions underlying critics’ arguments are highly questionable. Third, critics ignore morally significant realities of supply and distribution. Those who condemn so-called “booster” campaigns are distorting the moral dimensions of the problem at hand.

Regardless of one’s position on this issue, there is a tendency to use the term “booster.” But are these really boosters? The goal of re-vaccinating is to increase immunity back to protective levels after the immune system’s memory has faded. Many vaccines involve a priming dose and additional doses months later. But the later doses are not boosters.  Pointing to this, veteran vaccinologist Stanley A. Plotkin concludes that “booster” is immunologically inaccurate and that the later doses are actually “finishing” doses. We agree. It is also our view is that a dose’s status as a “booster” or “finisher” is not something that science alone reveals. Instead, its status is partly a function of moral deliberation; it turns on value-laden questions about the degree and duration of protection we owe to each other and the level of risk we find tolerable in our individual and social lives. 

The “booster” / “finisher” point cannot be dismissed as “mere semantics.” For that status is ethically significant in three ways. First, rhetoric matters. It determines what analogies and metaphors are apt, which pump intuitions and shape moral reasoning. “Booster” implies something like dessert after a meal, a luxury no one needs. Thus, Mark Ryan, director of the WHO’s health emergency program, constructs a lifejacket metaphor: “The fundamental, ethical reality is we’re handing out second lifejackets while leaving millions and millions of people without anything to protect them.” Second, the dose’s status determines the action one performs when administering it: If it is a finishing dose, then one is completing the three-dose regimen, or, borrowing from Ryan, completing the three-step action of providing a lifejacket. As is often true both in science and in life, we learn as we go. It seems we have learned that the Pfizer and Moderna vaccines are three-dose vaccines. The other side of this coin: the evolution of what it means to be “fully vaccinated.” Third, the way we conceptualize additional doses shapes our plans and actions in the future. Far from playing around with words, the “booster” / “finisher” point has significant practical import and deep-running moral implications.

One might reply that regardless of their status, the real moral question about these doses is: How can we use them to produce the greatest benefit? To be sure, allocating a dose to an LMIC-based vaccine-naïve individual (Person A) would produce a greater gain in individual-level immunity than would allocating that dose to an HIC-based individual who has already received two doses (Person B). However, it does not follow that allocating to A is morally obligatory. Nor does it follow that allocating to B is morally wrong. Critics’ arguments either assume that the moral conclusion follows directly from the immunological premise, or assume a suppressed premise, according to which the right allocation is that which produces the greatest increase in individual-level protection. But why assume either?

There are two reasons to reject these arguments and their assumptions. First, they ignore our special obligations to protect co-members of our communities. Second, they ignore the realities of vaccine supply, distribution, and administration. 

It is wrong to dismiss as ethically irrelevant the special obligations of community membership. Some partiality can be morally justified on the basis of special obligations we have by belonging to and occupying certain roles in our communities. Completing vaccination to attain maximum immunity for longer periods of time is not wrong simply because we choose to prioritize doing so among our neighbors and within our communities.

Critics tend to ignore the realities of current supply. The use of doses in enhanced vaccination campaigns does not explain—and is not to blame for—LMICs’ low coverage. Opponents also tend to ignore the logistical challenges of reallocating doses globally and the difficulties of administering doses in LMICs. The WHO’s lifejacket metaphor depicts radical scarcity and easy delivery: The agent has one lifejacket in hand, which she can easily toss to A or B. In reality, many doses are already distributed across the US. They are scattered across state facilities, pharmacies, administration sites, and other locales. Regathering them for redistribution to LMICs is unrealistic. Delivery would be technically difficult due to expiration, refrigeration demands, transportation, coordinating peripheral supplies, and several other factors. The lifejacket metaphor, which is trolleyology at sea, relies on logistical make-believe. It is a fiction that distorts our understanding of what we really can achieve and, therefore, what we really ought to do.

Rarely do these debates occur at the level of concrete facts. But the on-the-ground situation matters to whether moral reasoning is sound. We think it is crucial to distinguish between (1) ready-to-hand doses, which are already distributed across the US, and (2) in-the-works doses, which HICs may have purchased or intend to purchase but have yet to be produced or distributed. Different moral statuses attach to doses depending on where they are located in manufacturing timelines and supply chains because these facts determine what is feasible to do with them. Our view is that HICs are ethically justified when using ready-to-hand doses to enhance their vaccination programs. Doing so creates a real good, and doing otherwise is not feasible.

Recall the initial moral question: “Shall we use these doses as boosters at home, or shall we vaccinate the world?” Distinguishing between ready-to-hand and in-the-works doses unmasks the ambiguity of “these doses.” It also reveals that we can pursue both aims. 

It is easy to call for greater equality in the global distribution of COVID-19 vaccines. It is also something that we have a collective obligation to achieve through a thoughtful division of moral labor. However, too many voices are condemning HICs’ enhanced vaccination programs out of moral laziness. If global distribution is going to improve as it must, we must stop pretending that there is a trade-off between HICs’ domestic vaccination campaigns and vaccinating the rest of the world. Rather than indulging in ideologically driven fantasies, we must work with the realities of what the resource really is, where resources are located, and acknowledge the challenges of worldwide distribution.

Kyle Ferguson, PhD (@TheKyleFerguson) is a postdoctoral fellow in the Division of Medical Ethics at NYU Grossman School of Medicine

Arthur Caplan, PhD (@ArthurCaplan) is the Drs. William F. and Virginia Connolly Mitty Professor of Bioethics and the founding director of the Division of Medical Ethics at NYU Grossman School of Medicine


Caplan would like to acknowledge the support of a gift from Accenture for a project on ethics and vaccine boosters.

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