The coronavirus pandemic has spurred unprecedented efforts to find a vaccine. Billions have been poured into development, with yearslong timelines collapsed into months. A vaccine is widely seen as one of the essential tools for ending the current crisis. There are no fewer than 199 vaccines in development, 24 of which are already in clinical trials.
But, at the same time, there have been growing concerns that many people will not take up a COVID-19 vaccine when it arrives. One recent poll showed that one in three Americans would not try to get vaccinated; another showed that one in five would actively refuse to do so. This means that countries could fail to reach a level of uptake needed for herd immunity, which occurs when enough people are vaccinated to effectively halt the spread of the virus (protecting even those who didn’t receive the vaccination).
Given these challenges, in addition to actually creating one, we need a major push to understand how people will react to a COVID-19 vaccine. We believe that behavioral science can help. If this “last mile” of making vaccination easy, attractive, social, and timely is not bridged successfully, then a vaccine may have only limited impact—meaning much greater human, social, and economic costs.
In addition to actually creating one, we need a major push to understand how people will react to a COVID-19 vaccine.
This is not simple: there will be real barriers to uptake and legitimate questions about exactly how safe and effective a COVID-19 vaccine may be.
We already know that ensuring uptake of vaccines in general can be hard. Only 45 percent of adults in the United States got the flu vaccine in 2018–19; in 13 countries, uptake of the life-saving DTP infant vaccine (a combined vaccine protecting against diphtheria, tetanus, and pertussis) has fallen by 10 percentage points or more since 2015. We also know that behavioral science offers some simple strategies to increase vaccination, like reminders, incentives, and changing defaults.
But we also need to work out what specific behavioral challenges will arise for the COVID-19 vaccine. What do we know now, and what do we need to find out? Already, we can identify three areas to focus on: how we react to risks before a COVID-19 vaccine is available; the nature of the vaccine itself; and the way that risk varies by geography and groups.
Reacting to risks before a COVID-19 vaccine is available
A vaccine will not be available for some time. Before that happens, it is only realistic to think that many of us will want or need to take actions that increase our risk of exposure (e.g., travelling to work, visiting relatives). We can see three ways that this context may affect vaccine uptake: through rationalization, habituation, and rejection.
Rationalization: Rationalization may occur when we know that our actions may involve increased risk, but we carry them out anyway. We resolve this tension by changing our beliefs: for example, by thinking that an action actually is not too risky after all. The very fact that we need to function in a pre-vaccine world motivates us to think that we need a vaccine less, since we downgrade the risks present in that world.
There are specific features of COVID-19 that make rationalization more likely. First, there is the fact that many people who are infected do not experience any symptoms. An official study of 20,000 households in England found that around 70 percent of cases were asymptomatic; other studies have produced estimates of around 40-50 percent. Second, the known symptoms of COVID-19 have expanded away from the initial core of a fever and cough; the disease appears to present in many different ways.
If this “last mile” of making vaccination easy, attractive, social, and timely is not bridged successfully, then a vaccine may have only limited impact—meaning much greater human, social, and economic costs.
As awareness of these two points grows, it may make people more likely to rationalize their behavior by assuming that they have already had COVID-19, but just didn’t have symptoms like so many others. Or they may think back to any period of feeling unwell since early 2020 and attribute this to COVID-19. They may be correct, of course. But the risk is that people assume they are immune when they are not.
Habituation: In the second outcome, habituation, people simply factor in the risk of COVID-19 as “how life is now.” Unlike rationalization, people do not alter their perception of risks, they just perceive the risk in a “cold state” of acceptance, as opposed to a “hot state” of anxiety. In a more extreme form, this leads to fatalism—“If I’m going to get it, it will happen.” There is already evidence that the more infectious people think the virus is, the less likely they are to take mitigating actions. Both these states could reduce the desire to get vaccinated.
Rejection: We call the third mechanism rejection. Lockdowns and other policy responses have inflicted massive costs on lives and livelihoods. For some people, the fact that they have incurred this pain and restriction means they feel they have done enough to control COVID-19. In response, they may be determined to take actions, regardless of the risks. Unlike habituation, people may be actively rejecting the risks, angered by the costs that policy responses to COVID-19 have imposed on their lives. The inconvenience of getting vaccinated may be seen as just another of those costs.
The nature of the vaccine itself
In a world where we adjust to the existence of COVID-19, our attention may shift to new perceived risks instead. For example, the risks of the vaccine itself might grab more attention. With any new vaccine people may be uncertain and need assurances that it’s safe. But already there are concerns that the accelerated timelines for COVID-19 vaccines could lead to the perception that corners have been cut.
The fact that so many vaccines are being developed could also prove to be a problem. If just one or two have highly publicized negative side effects, then perceptions of the whole cohort could be affected, leading people to think all COVID-19 vaccines are unsafe. It’s likely that people will apply some mental heuristics here, and we need to find out exactly what they are.
In a world where we adjust to the existence of COVID-19, our attention may shift to new perceived risks instead. For example, the risks of the vaccine itself might grab more attention.
There is also the question of how effective the selected vaccines will actually be. People may be anchored on the idea that a vaccine will completely prevent someone from contracting COVID-19. After all, we do have vaccines that provide such “sterilizing immunity” (as is the case for measles), and these may inform people’s mental model of the COVID-19 vaccine.
In reality, the vaccine is likely to only reduce the likelihood of infection and limit the effects of COVID-19 (for example, by keeping it in the upper respiratory tract). It’s also possible that multiple doses may be needed. A shortfall in expectations could combine with concerns about rushed development to depress demand—particularly in lower risk groups, which takes us to our final point.
Varying risks by age and location
COVID-19 has inflicted a terrible toll of illness and death, and has rightly dominated global attention in 2020. But it also remains the case that incidence has varied greatly by geography, both within and between countries. At the same time, some groups have been affected more severely than others.
These variations could mean that the risks of COVID-19 are much less salient to some people, producing an attitude of “people here don’t need a vaccine” “people like me don’t need a vaccine.” This attitude could be bolstered if the vaccine is initially targeted at only certain groups (for example, health care workers or the elderly).
To be clear, these beliefs about lower risk may have some basis in fact, and a targeted rollout of the vaccine may be the best course of action. But we should also consider the effects on overall vaccine demand—particularly when it comes to lower risk groups. And perhaps the most striking feature of COVID-19 is the influence of age as a risk factor.
It’s quite possible that awareness of the lower risks to children will combine with concerns over the safety of a novel vaccine to increase parental opposition to having children vaccinated against COVID-19.
Many parents know that, unlike several other diseases, children appear to be spared most of the worst effects of COVID-19 (although there are some specific concerns). At the same time, vaccination of children has created many of the flash points in the anti-vax movement. Therefore, it’s quite possible that awareness of the lower risks to children will combine with concerns over the safety of a novel vaccine to increase parental opposition to having children vaccinated against COVID-19.
At this stage, with no vaccine finalized, we simply cannot know how justified those concerns will be. But we can and should urgently investigate people’s attitudes, beliefs, and likely behaviors related to a COVID-19 vaccine, in order to judge whether the ideas we outline above are real concerns.
What do we need to find out?
The first task is to collect data on how willingness or intent to receive a COVID-19 vaccine varies by factors like location, demographics, and the personal or local impact of the virus, as well as whether these views are changing over time. There is also an interesting question about whether observed levels of related behaviors, like mask wearing, could indicate likely future acceptance of a vaccine. Doing this research would provide a map of the challenges facing anyone trying to increase vaccine uptake.
Second, we need to understand people’s mental models and processes related to the risk of contracting COVID-19. In other words, we should establish if there is any empirical support for the ideas of rationalization, habituation, or rejection in the context of COVID-19. For example, people could be asked to rate the likelihood that they have had COVID-19 (and their reasons why). Then they could be offered an antibody test, recognizing that these tests are not perfect. Comparing these two data sources could help to identify when beliefs are accurate and when they could be the result of rationalization.
Third, we should explore people’s expectations and concerns about a potential vaccine itself. A first wave of surveying has examined concerns in a broad way. But we also need a more detailed understanding of people’s fears and expectations. Are people more concerned by a vaccine that is chimpanzee-derived than one that uses an inactivated form of the virus itself? Do people think the vaccine will be a once-and-done shot, or the start of a series of yearly visits?
Only by gaining this understanding can vaccine advocates consider effective ways of increasing uptake. Appropriately enough, one option is “inoculation theory”: by giving people a weakened version of misinformation in advance, along with refutations, they may be less likely to believe it in the future. But, like the vaccines themselves, much work is needed—soon—to turn these ideas into reality.