I did it. Most of my friends did it. Even Sen. Marco Rubio and other conservative leaders did it. And now some public health campaigns are trying to get everyone to do it: announce to the world with a social media post or “I Got Vaccinated” sticker that you rolled up your sleeve and got jabbed.

During the initial days of uncertainty as the COVID-19 vaccine was first rolled out, this social norming approach was a good strategy. Just a few short months later, however, it is not. In fact, continuing to promote “I Got Vaccinated” stickers risks creating a reverse effect and making vaccine hesitants even more entrenched in their views.

How could stickers be helpful and then suddenly not? To understand why, it helps to understand when social proof works and when it doesn’t, as well as what neurobiology can tell us about the power of “Us versus Them” as a driver of behavior.

“I Got Vaccinated” was a good strategy — at first. 

Social proof is a term coined by Robert Caldini in his 1984 book, Influence. It describes the tendency of humans to copy the behavior of others in ambiguous social situations where they are unsure how to behave.

In marketing circles, social proof is often short-handed to celebrity endorsements. But that shortcut misses a key component: uncertainty. Social proof works in contexts where it’s unclear how to act. A long ago (and hilarious) elevator experiment by psychologist Solomon Asch showed how you can get people to quickly abandon the common (and common sense) practice of facing the door of an elevator simply by having everyone except the unwitting subject face the rear.

But what is less often reported is that Asch’s experiments also showed that it takes just one other person defying a nonsensical norm to give experimental subjects the courage to defy the majority.

So what does that mean for covid vaccination? In the first few months of the year, when uncertainty was high and supplies were slowly expanding, having social influencers such as peers or political leaders showcase their shots likely helped reassure other people in their affinity groups that getting vaccinated was the right thing to do. (Since scarcity can make products more desirable, the lack of early vaccine supply also likely drove some demand.)

As we head into summer however, covid vaccines are widely available, except for in a few vaccine deserts. By now, nearly everyone who wanted a vaccine (or was easily persuaded) has gotten one. At this point in the pandemic, those same in-group social norms that may have persuaded the persuadable early in the vaccine rollout are now encouraging hesitants to dig in — and “I Got Vaccinated” stickers only makes it worse. Why? Because of Us versus Them.

How vaccine stickers can exacerbate in-group bias.

In his brilliant, dense and often humorous book Behave, neurobiologist Robert M. Sapolsky devotes a chapter to the in-group / out-group dynamics he calls “Us versus Them.”

From infancy, our brains are on high-alert for identifying our social in-group (primates do this, too). Our amygdala — the region of the brain that governs flight or fight stress responses — scans for visual cues and sorts people into “Us” or “Them” so fast that conscious thought can’t keep up. This leads to biases that can be detected via an Implicit Association Test (IAT) in a lab but that otherwise remain in the realm of the unconscious, leaving our conscious brains blissfully unaware.

The problem is that our brains do process those unconscious cues. But by the time they reach the surface, the person you are not even aware you are assessing has been sorted by your amygdala into an Us (one of the good, trustworthy people) or a Them (the people you need to watch out for).

Implicit bias has gotten the most attention for studies around subconscious reactions to race and gender. For example, in an IAT test in grad school recently, I was the only one among a dozen students who did not subconsciously associate women with family and men with career. (My husband, a South Dakotan who has taken over our household minding out of self-preservation, was not impressed.)

But Sapowsky notes that every person has multiple group identities. For example, the quickest way to subconsciously transform someone of another race or gender from an Us to a Them is to give the stranger a hat or T-shirt from a sports team you both root for.

Which leads us to vaccine stickers as an in-group identifier. Unfortunately, in our current dichotomized political environment, a vaccine sticker can be like a football jersey from the wrong team. It’s highly likely to signal “Us” to people who are probably already vaccinated, but to hesitants — the approximately 20% of Americans who aren’t a hard “no” but are dragging their feet — it’s more likely to signal a “Them.”

This is particularly problematic because hesitancy is largely driven by concerns about safety and trust. If I have questions and you’ve got an “I Got Vaccinated” sticker, it’s unlikely I’m going to trust you enough to ask. Instead, I’m going to assume you’re going to spout off at me with “fake news” or a sales pitch, along with a heaping dose of judgment.

So what can be done?

As anyone working to promote vaccine acceptance knows, there’s no easy answer. But here are some places to start.

1. Segment your messages. People are opposed to or hesitant about the covid vaccine for different reasons. The biggest pockets of hesitancy are Republican women and young adults, as well as people of color. Don’t think you can do one messaging campaign for all.
2. Invite questions. Hesitants have real concerns about the safety of the vaccine, and the emergency FDA approval process. Some are also worried about missing a day or more of work because of immediate side effects. Being open to listening requires a more nuanced approach, but trying too hard to convince people can backfire. As one commenter noted on a recent pro-vaccine social ad, “If this vaccine were so safe why am I seeing things like this several times a day. It definitely seems like they are trying to convince themselves.” 
   
3. Drop the “we are all in this together” theme. In research we conducted with vaccine hesitant residents in Maryland, the “do it for your community” message was off-putting. Hesitants tended to see themselves as independent thinkers (especially around personal health), valued control more than cohesion, and were skeptical of federal and medical authorities. In underserved communities, people questioned that getting vaccinated was truly the best way to “protect” their communities considering the many other challenges they face. A more effective message? In a recent KFF poll, telling people that the vaccines are nearly 100% effective at preventing hospitalization and death from covid made 41% percent of hesitants more likely to get a shot.
4. Make it easy to get it. Some hesitants are simply busy and not that worried about covid. Healthcare providers and employers can have a big role here by providing onsite vaccination drives and time off for a day of recovery. The KFF poll found that half of the hesitants said they would be more likely to get vaccinated if it were offered to them during a routine medical appointment and 37% said they would participate in on-site vaccinations at their workplace. Thirty-eight percent said they would be more likely to get vaccinated if their employer offered to pay them an extra $200.
5. Make it hard not to. For both hesitants and those in the hard “no” group, the poll showed travel and event restrictions could prove persuasive. Both groups said they would be more likely to get vaccinated if airlines or mass venues such as concerts required people to be vaccinated, or if the Centers for Disease Control and Prevention said vaccinated people could travel freely and unmasked. (But then again, a poll in Canada shows many unvaccinated people would simply lie to board a plane).

Whatever approaches you take to increase vaccine acceptance (as well as for your other behavior change campaigns), think deeply about how visual cues such as stickers can serve as invitations to join a welcoming in-group — or signifiers of a group of Thems your target audience doesn’t want to be part of.