By Invitation | Responding to covid-19

Katy Milkman on how to nudge people to accept a covid-19 vaccine

A catastrophe will unfold if people reject immunisations, but behavioural science can encourage people to do the right thing

By Katy Milkman

THE END OF covid-19 is in sight, as effective vaccines move closer to approval. However, society faces a new crisis: uptake. If too few people agree to get immunised, the value of a vaccine will be limited—and the world could face a situation much like today’s, with many ill and dying, social isolation and withering economies. But behavioural science can help.

Around 60-80% of the population will need covid-19 antibodies, either from a vaccine or from having recovered, in order to establish herd immunity, which protects the whole population. Around three-quarters of people in a sample of 15 countries say they will get vaccinated. But worryingly, although 33% of those surveyed “strongly agree” they’ll get immunised, a heftier 40% only “somewhat agree”—suggesting that a large share of the public may need prodding. The situation is more alarming in America. In May 72% of people said they would take a covid-19 vaccine when one became available. By September, however, that declined to just 51%.

Two distinct problems must be overcome. First, we need to persuade people who aren’t ideologically opposed to vaccines to get a jab. Second, we need to ensure that people willing to roll up their shirt-sleeve actually follow through. They require different strategies. (As for the hard-core anti-vaxxers, who are different from the vaccine-hesitant, they constitute a such a small portion of the American population, under 15%, that it’s reasonable to write them off and focus on those who will be easier to shift from the sidelines to the syringe.)

Start by considering “persuasion problems”. We need to assuage the concerns about side-effects and safety that are unfounded. Those who have little to fear personally from a coronavirus infection, like young adults, will also need convincing.

Relying on information, transparency and encouragement is only the start. “Social proof” also needs to be part of the effort. Research shows that people look to their peers for cues about how to behave, affecting everything from voting to savings. So health authorities should emphasise the wide support for vaccinations rather than focusing on naysayers. Public-service messages highlighting the popularity of the vaccine would not only be accurate but should increase demand.

The more visible we can make it when people get vaccinated, the better. The “I Voted” stickers that Americans receive at the polls may seem like small rewards for doing one’s civic duty, but they’re also advertisements that can spur others to follow suit. Hence, after getting jabbed, people should be encouraged to text their friends, post on social media and sport “I got the covid-19 vaccine” stickers.

Seeing widespread adoption of a vaccine will calm many people’s fears about safety. And if members of low-risk groups see their friends clamouring to get vaccinated, they are likely to queue up, too. It will be critical to ensure that segments of the population that have typically been underrepresented in getting vaccines, such as racial minorities, make up a big part of marketing efforts.

Those on the fence may also be persuaded by the traditional mechanisms of mandates and rewards. Requiring health-care workers and students to get vaccinated would follow precedent, and not only protect them but build community-vaccination norms, too. As for paying people to get inoculated, it may attract some but it could backfire: the more people are paid to do something, the more they infer it entails substantial risks. So the approach would need testing.

Another difficulty is combating misinformation. Research suggests that Facebook, Twitter and others could help by altering their algorithms to up-rank content on vaccines from trusted sources and prompt people to consider the accuracy of news before sharing. Furthermore, since we look to authority figures for validation of our beliefs, fears and conspiracy theories, it will also be critical for leaders from across the political spectrum to present a unified message about the value of vaccines.

After tackling the persuasion problem, the second behavioural challenge is the follow-through problem. It will shock many to learn that anywhere from a third to two-thirds of people who say they’ll do something, such as get a medical check-up or exercise, fail to act on their intention (or, as it’s called in the scholarship, they “flake out”). Follow-through problems crop up everywhere, explaining both why many registered voters fail to show up at the polls and the profitability of mail-in rebates (few are ever redeemed).

Follow-through problems won’t disappear even when it comes to getting vaccinated during a deadly pandemic. We label those who do not feel strongly about something as “on the margin”; following-through just isn’t a priority for them. At the very least, the 20% of Americans who changed their minds about getting a vaccine between April and September are probably on the margin. So even if they can be persuaded to flip their stated intentions, many still may not follow through.

To make matters worse, the most promising vaccines, from Pfizer, Moderna and AstraZeneca, will not be “one-and-done”. Instead, they will require people to get two inoculations several weeks apart. This dramatically increases the risk of follow-through problems. If we don’t lay the right groundwork, many people will get the first shot but not the second.

Thankfully, behavioural scientists know how to promote follow-through and we’re about to learn more. In anticipation of the need to foster covid-19 vaccine uptake, my colleagues Angela Duckworth, Mitesh Patel and I convened a team of more than 100 behavioural scientists to conduct two unusually large and complex social-science experiments to learn what improves follow-through.

In one study with Walmart, which operates more than 4,700 pharmacies in America, we are testing the effectiveness of text messages to hundreds of thousands of patients who had previously opted in to receive texts from their pharmacy. The idea is to see which messages most effectively spur people to get a seasonal-flu vaccine, which is a sort of proxy for covid-19. Getting this right could have a huge impact: Walmart serves 150m customers a week and 90% of Americans live within ten miles, or 16 kilometres, of a store. We are also running a similar trial with two large, regional health systems, Penn Medicine and Geisinger.

Ideas being evaluated include whether it helps to indicate that a dose is “reserved and waiting for you”. We’re also exploring whether spurring friendly regional rivalries can increase inoculations—for example, by prompting stalwart Pennsylvanians to beat louche New Yorkers. And we’re evaluating whether just-in-time reminders to get vaccinated sent minutes before a medical visit are more effective than reminders sent farther in advance.

We already know it will be critical to make vaccinations convenient so people won’t be dissuaded by hassle factors: inconveniences like paperwork or waiting in line. Ideally, vaccines would be free, take just a few minutes and be available at every drugstore (though cold-temperature storage makes this tricky). We also need vaccination to go on everyone’s calendar. Simply informing people they have an appointment—with an easy way to reschedule—boosts flu vaccination by 36%.

In cases where offering a default appointment isn’t feasible, we should prompt people to plan when and where they’ll get their jabs. Mailing people letters that ask them to consider the date and time they’ll get inoculated increases flu immunisation by 12%. Once both vaccination jabs are scheduled, we’ll need to nag people. In a recent medical study, researchers found that pestering patients with text-message reminders and phone calls until they confirmed that they had followed through on their doctors’ orders improved treatment outcomes by 10%.

Finally, we don’t want people to dread the vaccine. The more we dread something, the more we put it off; but when we expect instant gratification, we’re more inclined to take healthy actions. So ideally, we’d find ways to make it fun to get vaccinated.

The economist and Nobel laureate Richard Thaler has suggested giving everyone who gets immunised a lottery ticket (which should feel more like a prize than a payment). My own admittedly over-the-top proposal is that health organisations lease fleets of ice-cream trucks to drive around playing a catchy jingle and offering a free vax and cone—convenience, social visibility and a dose of fun, all in one.

The serious point is that we need to think not just carefully but creatively. The biochemists have done their part. It’s now time for the work of behavioural scientists to move the needle.

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Katy Milkman is a professor of Operations, Information and Decisions at the Wharton School of the University of Pennsylvania where she co-directs the Behavior Change for Good Initiative. She is the president of the Society for Judgment and Decision Making and hosts the podcast Choiceology. Her book “How to Change: The Science of Getting From Where You Are to Where You Want to Be” (Portfolio) will be published in 2021.

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