Pelé, Dolly Parton and the Dalai Lama have little in common: for a few days in March, they became the latest celebrity case studies on the health benefits of Covid-19 vaccines.
"I just want to tell all the cowards out there, don't be such a squat," said Ms. Parton, 75, in a video she posted on Twitter after receiving her vaccine in Tennessee. "Go out there and get your shot."
This is hardly the first time public figures have cast their popularity behind efforts to change the behavior of ordinary people. In medicine, celebrities tend to mirror or reinforce messages that health officials are trying to get public, regardless of whether they are receiving a vaccine or other medical treatment. In 18th century Russia, Catherine the Great was vaccinated as part of her campaign to promote the nationwide introduction of the smallpox process. Almost 200 years later, behind the scenes on the Ed Sullivan Show, Elvis Presley received the polio vaccine to reach teenagers at risk.
But do the starred endorsements really work? Not necessarily. Epidemiologists say there are many reservations and potential pitfalls – and little scientific evidence that the endorsements actually increase vaccine uptake.
"Very few people give celebrities the weight of expertise, good or bad," said René F. Najera, epidemiologist and editor of the History of Vaccines website, a project by the Philadelphia College of Physicians.
"There are now some shifts there with social media and social influence in the younger age groups," he added. "But for the most part, we still listen more to our colleagues than to a figurehead."
As vaccination campaigns accelerate around the world, watching high profile endorsements has become one of the newest – and some of the weirdest – online rituals of the Covid era.
To keep track of the phenomenon, New York Magazine kept a list of newly vaccinated celebrities over the winter, including Christie Brinkley ("Piece of Cake"), Whoopi Goldberg ("I Didn't Feel It") and Mandy Patinkin ("One") few advantages of getting older ”). Journalists in India have done the same for Bollywood movie stars.
In Europe, images of male politicians photographed shirtless have spawned a number of memes. An Oregon epidemiologist, Dr. Esther Choo joked on Twitter that French Health Minister Olivier Véran was running a public relations campaign she called "Operation Smolder".
Such posts are noteworthy because they instantly enable millions of people to see the raw mechanics of immunization – needles and everything – at a time when skepticism about Covid vaccines has been persistent in the US and beyond. The rapid-fire testimonials from Pelé, Ms. Parton and the Dalai Lama in March, for example, reached a combined total of more than 30 million followers and led to hundreds of thousands of engagements on Twitter, Instagram and YouTube. In April, singer Ciara hosted an NBC star-studded vaccination promotion special with performances by former President Barack Obama and his wife Michelle Obama, as well as Lin-Manuel Miranda, Jennifer Hudson, Matthew McConaughey, and others.
"These types of endorsements could be especially important when trust in government / official sources is quite low," said Tracy Epton, a psychologist at the University of Manchester in the UK who has studied public health interventions during the coronavirus pandemic , in an email.
April 30, 2021, 9:52 p.m. ET
This was the case in the 1950s when Elvis Presley agreed to receive the polio vaccine to help the National Polio Foundation reach a demographic of teenagers “difficult to raise and use by traditional means to be inspired, ”said Stephen E. Mawdsley. Lecturer in Modern American History at the University of Bristol in the UK.
"I think Elvis helped make vaccination seem 'cool' and not just the job in charge," said Dr. Mawdsley.
There is evidence that celebrities who advocate certain medical behavior can achieve concrete results. For example, after Katie Couric had a colonoscopy on "Today" in 2000, the number of colon exams in the US increased for about nine months.
In Indonesia, researchers in a pre-coronavirus experiment found that 46 celebrities who agreed to tweet or retweet pro-immunization messages were more popular than similar ones from non-celebrities. This was especially true when the celebrities delivered the message in their own voices rather than quoting someone else, researchers found.
"Your voice matters," said Vivi Alatas, an economist in Indonesia and co-author of this study. "It's not just their ability to reach followers."
For the most part, however, the science associating celebrities with behavior change is difficult.
One reason for this is that people generally view those on their own personal networks, rather than celebrities, as the best sources for advice on changing their own behavior, said Dr. Najera.
He cited a 2018 study that found few gun owners in the U.S. rated celebrities as effective communicators for keeping guns safe. The owners were far more likely to trust law enforcement officers, active duty military personnel, hunting or outdoor groups, and family members.
Dr. Najera and other researchers have convened focus groups of Americans to find out what made them agree – or not – to be vaccinated against Covid-19. He said the main finding so far has been that admission rates or hesitation often matched the vaccination behavior of a particular person's racial, ethnic, or socio-economic peer group.
Ho Phi Huynh, a professor of psychology at Texas A&M University in San Antonio, said that celebrity vaccine endorsements tend to have a "spectrum of action," as the degree of star admiration varies widely from fan to fan. Some see a celebrity only as entertainment, said Dr. Huynh, while others form bonds with her that can make up for a lack of authentic relationships in their own lives.
"Back to Dolly, if people perceive her as a 'typically liberal' celebrity, there might be little leverage for a large faction in the country," he said.
In Indonesia, it took just a few hours this winter for a mega-celebrity to undercut their own vaccine certification.
The government had selected the entertainer Raffi Ahmad, 34, as one of the first in the country to receive a Covid shot in January. "Don't be afraid of vaccines," he told his Instagram followers, who at the time were nearly 50 million, almost a fifth of the country's population.
That night he was seen parting without a mask and accused of breaking the public's trust.
"Please, you can do better," Sinna Sherina Munaf, an Indonesian musician, told Ahmad and her nearly 11 million followers on Twitter. "Your followers are counting on you."