In recent months, the media has called on celebrities to open up about their COVID vaccination status. Immunity is a shared space, the argument goes, and pro-vaccine pop-stars can convince the public that getting immunized isn't just a personal choice. There's some truth to this, but the argument raises touchy ethical questions about privacy that need to be answered.
Should celebrities tell the world that they've been vaccinated against COVID-19? Going back to April, media personalities like CNN's Brian Stelter have criticized other high-profile news anchors for not advertising their immunization status, and thus failing to set a good example for the general public.
The argument has yet to die down as the media continues to suggest that celebrities who stay silent about the vaccines are threatening public health. New Republic contributor Marion Renault outlined that case in a June 24 story:
Athletes, influencers, and other public figures have discovered a rhetorical escape hatch from uncomfortable conversations about the Covid-19 vaccine: It’s none of your business. But vaccines for infectious diseases are, by nature, everyone’s business. Getting the jab not only protects the recipient from getting seriously sick or dying from Covid-19; it also reduces a person’s risk of carrying and transmitting the virus to anyone around them, too.
That last sentence is certainly correct; the vaccines work very well. But we need to qualify the rest of the argument. First, celebrities can influence public behavior under certain circumstances, though they aren't nearly as influential as is often assumed. Second, people value their privacy. Failing to recognize this fact can offset the benefits that come from celebrity vaccine endorsements.
Just how influential are celebrities?
As always, answers to this type of question are complicated. Celebrities can influence our health care decisions, but their persuasive talents are context-dependent. This is, in part, because people don't consume media in a vacuum. When celebrities speak out about contentious issues, vaccination, for example, their messaging competes with the audience's preexisting views.
University of Tennessee political science researcher Anthony Nownes examined this dynamic in a 2011 study. Nownes split 500 people into three groups and asked two (the third was a control group) how they felt about Jennifer Aniston and Peyton Manning, the former an outspoken Democrat and the latter a Republican. He collected data on the participants' political views and surveyed them before and after the experiment. The evidence he gathered suggested
that if celebrities want to help the parties they support by 'going public' with this support, they may have a hard time doing so. I say this because Jennifer Aniston’s impact on people’s views of the Democratic Party was only negative. In addition, Peyton Manning’s effects on respondents’ views of the Republican Party were positive, but quite modest.
The effect can also run in the opposite direction, Nownes added:
The data show that people who are not particularly fond of Republicans are turned off by Peyton Manning’s support for the Grand Old Party (GOP) and adjust their opinions of him accordingly. Similarly, people who dislike the Democratic Party view Jennifer Aniston more negatively after learning about her support for Democrats.
More recent research investigating this phenomenon has reached similar conclusions. For instance, a study that asked voters how they felt about celebrity Congressional testimony found that it had no greater impact compared to non-celebrity testimony. Interestingly, the celebrity testimony generated much more media coverage, suggesting “that celebrity is itself a media-constructed concept and that media coverage does not always result in attitude change among the general public,” Skeptical Inquirer noted. 
Nownes explained in a 2019 study that celebrity involvement in political causes can signal to the public that “If Celebrity X thinks the issue is important, it must indeed be important.” However, that's a bit different than determining how people will react to that agenda. Research has also shown that consumers of media care about the content, and react to it based on how relevant they deem the information to be. According to a 2007 paper:
Rather than simply relying on what is accessible in memory, people pay attention to the content of news stories and make judgments about national importance based on that content … [P]eople pay careful attention to current information gleaned from the media and use it to update and adjust a host of heretofore unrecognized political evaluations.
So, how do we make sense of these contrasting studies? Xavier Symons, a postdoctoral research fellow at Australian Catholic University's Plunkett Centre for Ethics summed it up this way in an email:
I think the conflicting results have to do with the kinds of celebrities involved. I think there is a perception among some in community that Hollywood is (with a few exceptions) in lockstep with a liberal elite, and so Hollywood celebrity endorsements of vaccination may have a negative impact on the attitudes of a certain portion of the population.
But I think this is an issue of ensuring that the right public figures come out and endorse vaccination. It's particularly important that religious leaders, conservative commentators, sportspeople and ethnic community leaders endorse vaccination as they are more closely aligned with vaccine hesitant groups. Trump getting vaccinated on TV is much more valuable than Biden getting vaccinated on TV.
But what of Renault's underlying claim, that your vaccination status is “everyone's business”?
We want to think of health as a personal project … But that’s not how it works … preventing the spread of disease requires sometimes disclosing our health status to others. I am free to refuse to answer when a sexual partner asks me if I’ve tested positive for an STD, but my withholding limits their ability to make informed decisions about their own health.
True enough, but this line of reasoning undervalues the importance of confidentiality in health care. Confidentiality often motivates patients to seek appropriate medical treatment. The more we insist that “talking about the vaccine is a vital public health activity,” to use Renault's phrasing, the less likely the unvaccinated may be to get a COVID shot.
Humans are weird. We have a desire to fit in with the crowd, which is why celebrity endorsements work and can be used to promote immunization. But we also don't like being lectured about intimate aspects of our lives; in fact, when told to change our behavior, we tend to amplify the behavior in question. If we want to bypass this innate quirk in human nature and boost COVID vaccine uptake, the evidence suggests we need to earn the public's trust, and that starts with respecting their autonomy.
Hat tip to Skeptical Inquirer for publishing that story, which sent me down a PubMed rabbit hole.