A COVID-19 vaccine shot is administered at the Mount Sinai South...

A COVID-19 vaccine shot is administered at the Mount Sinai South Nassau Vaxmobile visit at Freeport High School in 2021. Credit: Newsday/Steve Pfost

People living in Republican-leaning states are much more likely to report severe adverse reactions to the COVID-19 vaccine than those in Democratic-leaning states, a study released Friday found.

The study, published online on the American Medical Association's JAMA Network Open, found that as the percentage of a state's votes for former President Donald Trump in the 2020 election increased, so did reports of "adverse events" to the federal government’s Vaccine Adverse Event Reporting System. A 10% increase in Republican voting was associated with a 25% increase in the chances that a severe adverse event would be reported.

For example, there were about four reports of severe adverse events per 10,000 vaccinated people in Kentucky, where Trump received more than 60% of the vote, but fewer than one report per 10,000 vaccinated residents in California, where President Joe Biden got more than 60% of the vote. 

Multiple studies have shown the vaccine rarely causes serious problems, and experts attributed the partisan gap to the politicization of vaccines, pointing to research showing more vaccine skepticism among Republicans than Democrats.

People who already are suspicious of vaccines or regularly hear rhetoric against them are more likely to believe an illness or death that occurred after immunization was caused by the vaccine, said Jennifer Kates, a senior vice president at the San Francisco-based health policy nonprofit KFF who was not involved in the study.

“People could attribute any kind of experience they may have after getting a vaccine to the vaccine, when in most cases, it's not related to the vaccine at all, it's related to something else in their life,” said Kates, who has researched partisan differences in vaccine attitudes. “People die every day. Someone might die after they get a vaccine. That doesn't mean it was the vaccine that caused it.”

Researchers in the study analyzed 620,456 reports from 2020 to 2022. Effects were considered severe if they threatened or caused death, or led to emergency visits, hospitalizations or disability, the study states.

Despite overwhelming statistical evidence that the vaccines are safe, people are susceptible to anecdotes, even if the anecdotes are not always accurate, said Dr. David Asch, a professor of medicine at the University of Pennsylvania and co-author of the study.

“We are very moved by narratives and anecdotes, and very unmoved by statistics,” he said. “And yet it's the systematic collection of data that has more truth in it.”

Someone who has a preconception that the vaccine is unsafe and hears that a person died or contracted an illness after immunization is more likely to connect that death or illness to the vaccine than someone who believes the vaccine is safe, he said.

One potential serious effect is myocarditis, an inflammation of the heart muscle that — although rare — is more common in young men and adolescent boys than in others. But COVID-19 also can cause inflammation, and one study found the risk of myocarditis is much higher from a COVID-19 infection than from the vaccine, even in males 12 to 17.

A January 2022 study for which Kates was the lead author found that vaccination rates were higher in counties that voted for Biden in 2020 than in those that voted for Trump. Studies have found that after vaccines became available, COVID-19 death rates were much higher in Trump-leaning counties than in ones that voted for Biden.

Some who reported vaccine-related adverse events for themselves may not have been enthusiastic about receiving the vaccine, said Matthew Motta, an assistant professor of health law, policy and management at Boston University.

“They could be vaccine skeptics who nevertheless had to vaccinate because there was a statute in place requiring them to do so,” he said.

Motta has co-authored several studies that found partisan differences in vaccine-related attitudes and actions.

One found a link between anti-vaccine coverage on Fox News and reports submitted of negative effects of vaccines.

“As right-leaning news coverage becomes more negative, we tend to see increases in vaccine adverse event reports,” Motta said.

Even before COVID-19, Republicans were more likely to be skeptical of vaccines, Motta said. That may be in part because of beliefs on individual liberty or religious beliefs, he said.

But the skepticism about the COVID-19 vaccine on the right has spilled over to other vaccines, including childhood vaccines for measles, mumps, rubella and varicella, he said.

A study Motta co-authored last year found more reports of adverse events from vaccinations against measles, mumps, rubella and varicella in Republican-leaning states before 2020 — but that number “spiked dramatically” after the COVID-19 vaccine became available.

“People are looking at vaccines and vaccinations in a new and politicized way, and that’s coming to shape the way they view all vaccines,” he said.

People living in Republican-leaning states are much more likely to report severe adverse reactions to the COVID-19 vaccine than those in Democratic-leaning states, a study released Friday found.

The study, published online on the American Medical Association's JAMA Network Open, found that as the percentage of a state's votes for former President Donald Trump in the 2020 election increased, so did reports of "adverse events" to the federal government’s Vaccine Adverse Event Reporting System. A 10% increase in Republican voting was associated with a 25% increase in the chances that a severe adverse event would be reported.

For example, there were about four reports of severe adverse events per 10,000 vaccinated people in Kentucky, where Trump received more than 60% of the vote, but fewer than one report per 10,000 vaccinated residents in California, where President Joe Biden got more than 60% of the vote. 

Multiple studies have shown the vaccine rarely causes serious problems, and experts attributed the partisan gap to the politicization of vaccines, pointing to research showing more vaccine skepticism among Republicans than Democrats.

WHAT TO KNOW

  • A study published online in the American Medical Association's JAMA Network Open found that as the percentage of a state's votes for former President Donald Trump in the 2020 election increased, so did reports of "adverse events" to the federal government’s Vaccine Adverse Event Reporting System.
  • Multiple studies have shown the vaccine rarely causes serious problems, and experts attributed the partisan gap to the politicization of vaccines, pointing to research showing more vaccine skepticism among Republicans than Democrats.
  • Skepticism about the COVID-19 vaccine on the right has spilled over to other vaccines, including childhood vaccines for measles, mumps, rubella and varicella.

People who already are suspicious of vaccines or regularly hear rhetoric against them are more likely to believe an illness or death that occurred after immunization was caused by the vaccine, said Jennifer Kates, a senior vice president at the San Francisco-based health policy nonprofit KFF who was not involved in the study.

“People could attribute any kind of experience they may have after getting a vaccine to the vaccine, when in most cases, it's not related to the vaccine at all, it's related to something else in their life,” said Kates, who has researched partisan differences in vaccine attitudes. “People die every day. Someone might die after they get a vaccine. That doesn't mean it was the vaccine that caused it.”

Researchers in the study analyzed 620,456 reports from 2020 to 2022. Effects were considered severe if they threatened or caused death, or led to emergency visits, hospitalizations or disability, the study states.

Despite overwhelming statistical evidence that the vaccines are safe, people are susceptible to anecdotes, even if the anecdotes are not always accurate, said Dr. David Asch, a professor of medicine at the University of Pennsylvania and co-author of the study.

“We are very moved by narratives and anecdotes, and very unmoved by statistics,” he said. “And yet it's the systematic collection of data that has more truth in it.”

"We are very moved by narratives and anecdotes, and very...

"We are very moved by narratives and anecdotes, and very unmoved by statistics," said co-author Dr. David Asch, a professor of medicine at the University of Pennsylvania. Credit: Penn Medicine

Someone who has a preconception that the vaccine is unsafe and hears that a person died or contracted an illness after immunization is more likely to connect that death or illness to the vaccine than someone who believes the vaccine is safe, he said.

One potential serious effect is myocarditis, an inflammation of the heart muscle that — although rare — is more common in young men and adolescent boys than in others. But COVID-19 also can cause inflammation, and one study found the risk of myocarditis is much higher from a COVID-19 infection than from the vaccine, even in males 12 to 17.

A January 2022 study for which Kates was the lead author found that vaccination rates were higher in counties that voted for Biden in 2020 than in those that voted for Trump. Studies have found that after vaccines became available, COVID-19 death rates were much higher in Trump-leaning counties than in ones that voted for Biden.

Some who reported vaccine-related adverse events for themselves may not have been enthusiastic about receiving the vaccine, said Matthew Motta, an assistant professor of health law, policy and management at Boston University.

“They could be vaccine skeptics who nevertheless had to vaccinate because there was a statute in place requiring them to do so,” he said.

Motta has co-authored several studies that found partisan differences in vaccine-related attitudes and actions.

One found a link between anti-vaccine coverage on Fox News and reports submitted of negative effects of vaccines.

“As right-leaning news coverage becomes more negative, we tend to see increases in vaccine adverse event reports,” Motta said.

Even before COVID-19, Republicans were more likely to be skeptical of vaccines, Motta said. That may be in part because of beliefs on individual liberty or religious beliefs, he said.

But the skepticism about the COVID-19 vaccine on the right has spilled over to other vaccines, including childhood vaccines for measles, mumps, rubella and varicella, he said.

A study Motta co-authored last year found more reports of adverse events from vaccinations against measles, mumps, rubella and varicella in Republican-leaning states before 2020 — but that number “spiked dramatically” after the COVID-19 vaccine became available.

“People are looking at vaccines and vaccinations in a new and politicized way, and that’s coming to shape the way they view all vaccines,” he said.

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