When Trump endorses COVID shots, vaccinations jump

A video compiled from Fox News clips of former President Trump and his family urging his supporters to get vaccinated against COVID-19 proved to be a cheap and effective way to convince some vaccine skeptics to get their shots.

In a large-scale ad experiment published today , a team of researchers from UC Berkeley’s Haas School of Business, Stanford University, University of North Carolina at Chapel Hill, and North Carolina State University compiled a public service announcement from existing footage and aired it on YouTube channels-including Fox News- channel-in more than 1,000 U.S. counties with low vaccination rates. Compared with similar counties where the ad wasn-t shown, those counties recorded 104,036 additional vaccinations, at a cost of less than $1 per new shot.

The randomized controlled trial proved the researchers- hunch that a partisan message would be a potent way to overcome the entrenched partisan divide around COVID-19 vaccines, according to co-author Steven Tadelis , professor of business and public policy at the Haas School of Business. It was also relatively inexpensive.

"Creating an intervention that effectively costs about $1 per extra vaccine is remarkably cost-effective, and a small fraction of the cost of other interventions,- Tadelis said, noting that studies of U.S. state vaccine lotteries put the cost at $68 to $82 per vaccine. Offering people direct compensation for getting vaccinated in Sweden put that cost at $24.



"Creating an intervention that effectively costs about $1 per extra vaccine is remarkably cost-effective, and a small fraction of the cost of other interventions.- -Steven Tadelis, Berkeley Haas

Using politics to overcome the political divide

Data from the Kaiser Family Foundation found that among the 27% of American who remained unvaccinated as of October, 60% identify as Republicans and just 17% as Democrats. Counties that voted heavily for Trump experienced COVID-related death rates nearly three times higher than counties that voted heavily for Joe Biden, an NPR analysis found.

Although Trump spearheaded Operation Warp Speed and he and former First Lady Melania Trump got their shots as soon as the vaccine was available, Trump did little to encourage vaccine uptake. Meanwhile, messaging from the Centers for Disease Control and Prevention (CDC) and medical experts about the vaccine’s efficacy has been overshadowed by a drumbeat of skeptical Fox News personalities who are also among Trump’s biggest boosters.

-We felt like there should be a better way to send a message that would resonate with people on the right,- said Stanford economics professor Brad Larsen , lead author of the study, in a press release.



-We felt like there should be a better way to send a message that would resonate with people on the right.” -Brad Larsen, Stanford University



The National Bureau of Economic Research working paper was co-authored by political science professors Timothy Ryan , Marc Hetherington , and Rahsaan Maxwell from the University of North Carolina at Chapel Hill and Steven Greene from North Carolina State University.

Creating the experiment

The researchers received funding for the experiment from the Vaccine Confidence Fund , and it was approved under the Institutional Review Board at Stanford University.

They hired a professional video editor to create a 27-second public service announcement with an upbeat soundtrack. It opens with the Fox 13 News Utah anchor declaring, -Donald Trump is urging all Americans to get the COVID-19 vaccine.- It then cuts to a phone interview in which Fox News anchor Maria Bartiromo nods in agreement while then-President Trump says, -I would recommend it, and I would recommend it to a lot of people that don-t want to get it, and a lot of those people voted for me, frankly.-

Next is another clip of the Fox 13 News Utah anchor explaining, -Both Trump and former First Lady Melania Trump did receive their vaccines privately in January at the White House.- The final shot shows a social media post Ivanka Trump shared when she got her jab. The ad closes with the statement, -Your vaccine is waiting for you.- It also includes a link back to the original broadcast.

The research team spent just under $100,000 on YouTube’s advertising platform, Google Ads, to air the video in counties with vaccination rates below 50%. The video was pushed out to 1,083 counties across the U.S. from Oct. 14 to 31, 2021. The study included a control group of 1,085 similar counties that did not receive the ad.

While the researchers had no control over which channels it would appear on, the Google Ads- algorithms sent it most often to Fox News- YouTube channels, where it was attached to segments hosted by Laura Ingraham, Tucker Carlson, Sean Hannity, and other Trump supporters and vaccine skeptics. It also appeared on some neutral channels and some not supportive of Trump, including Saturday Night Live, MSNBC, and NBC News.

Overall, the ad appeared on more than 150,000 YouTube channels and was delivered to more than 6 million viewers, resulting in 11.5 million impressions.

The researchers used data from the CDC on the number of vaccines administered in each county from one month before and month after the campaign to analyze the effect.

Their findings:

  • The number of vaccinations in the average county where the ad was shown increased by 103, with a total of 104,036 additional vaccines in all (compared with counties where the ad was not shown).
  • With an advertising budget just below $100,000, that amounted to about $1 for each additional vaccine.
  • More intensive advertising made a difference: An increase of 1,000 ads led to 8.6 additional vaccines on average. Put differently, 116 ad impressions were required to yield one additional vaccine.
  • While the ads moved some skeptics to action, they were only effective in counties with up to 70% Trump voters. The heaviest pro-Trump counties were unmoved.


- Using Donald Trump’s COVID-19 Vaccine Endorsement to Give Public Health a Shot in the Arm: A Large-Scale Ad Experiment -
By Bradley J. Larsen, Timothy J. Ryan, Steven Greene, Marc J. Hetherington, Rahsaan Maxwell, and Steven Tadelis
National Bureau of Economic Research, April 4, 2022

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