(Bloomberg) -- Negative reporting on Covid-19 shots that aired on Fox News was linked to increased vaccine hesitancy, according to a new study that shows how the nation’s No. 1 news network influenced viewers during a pandemic that has killed more than 1.1 million people in the US.

Concerns about the safety of Covid vaccines as measured in reported side effects increased following heightened periods of negativity in Fox News coverage of vaccines, according to the study published Wednesday in the journal Political Communication. Public opinion surveys also showed Fox viewers reported elevated levels of vaccine hesitancy throughout the pandemic compared to regular viewers of other programs. 

“When Fox News’ negativity about vaccines goes up, so too does vaccine hesitancy. When it goes down, so too does vaccine hesitancy,” said Matthew Motta, a professor of health policy at the Boston University School of Public Health.

Earlier research has demonstrated that viewers of Fox viewers were less likely to be vaccinated than people who got their news elsewhere. Exposure to online misinformation has been linked to vaccine hesitancy, as has consumption of information from conservative and fringe sources. But the new findings highlight the power the network and other information sources have had to sow distrust among viewers.

To demonstrate this, Motta and his collaborator Dominik Stecula, a political scientist at Colorado State University, turned to the Vaccine Adverse Event Reporting System, a government-run monitoring program that helps spot problems with shots early on. For example, the rollout of the Johnson & Johnson Covid shot was paused after nearly 7 million doses were administered because just six cases of blood clots were reported to VAERS.

Anyone can report adverse reactions to the clearinghouse — whether or not they’re associated with vaccination — and they’re published without fact-checking to show they really occurred. Anti-vaccine groups at times have encouraged followers to file reports to VAERS, aiming to sow doubts about safety. Facebook videos of people reading lists of these reported side-effects have gone viral.

Measuring Opinion

Motta and Stecula used the database as a proxy for public perception of Covid vaccines. Typically, you would expect to see reports of side effects distributed regularly over time as the vaccines rolled out and more Americans were immunized.

Instead, the analysis found that increases in reports of side effects tended to follow negative coverage of the vaccines on Fox News. Public opinion surveys conducted by the pair backed up their findings.

“There’s a remarkable correlation between VAERS reports and use of the anti-vaccine themes and the reporting that's done on the virus on Fox,” Stecula said.

Fox News didn’t respond to requests for comment. Fox has said that the network has aired pro-vaccine public service announcements and that a number of its on-air personalities have supported vaccination. The outlet reaches more than 2 million weekday primetime viewers daily. 

In the early days of the vaccine rollout, huge numbers of Americans delayed getting vaccines, keeping the virus in circulation and putting the most vulnerable at increased risk. Today, while 81% of eligible Americans have received at least one shot, less than 70% have completed their primary vaccine series and only 16% have received the updated bivalent booster that became available last fall.

Fox News did not respond to requests for comment. Fox has said that the network has aired pro-vaccine public service announcements and that a number of its on-air personalities have supported vaccination. The outlet reaches some 2 million weekday primetime viewers daily. 

Usually, when viewers have direct experience with a disaster or another event news programming generally holds less influence. People don’t need a news anchor to tell them what’s going on when they’re in the middle of it.

But in this case, living through the pandemic didn’t diminish the power that Fox held over its audience.

“Content matters,” said Motta. “It matters what folks say on the airwaves, because those words can change people's attitudes and behaviors. It's a little scary.”

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