Updated March 29, 2025 at 12:04 PM ET
When the COVID-19 pandemic hit, there was a moment when some people thought it could be a unifying time for the U.S., like the way Americans came together in the aftermath of the Sept. 11, 2001, terrorist attacks.
But Matt Motta, a professor at Boston University's School of Public Health who studies anti-science attitudes, remembers when he first felt convinced that the pandemic would divide Americans instead.
It was just over five years ago: March 24, 2020. At that point, many states and municipalities had shut down, and people were staying at home in an effort to reduce the spread of the virus and prevent hospitals from becoming overwhelmed by COVID-19 patients.
President Trump appeared on Fox News and said life should return to normal by Easter, which was less than three weeks away. "I think Easter Sunday, you'll have packed churches all over our country," Trump said. "I think it would be a beautiful time."
Those statements were at odds with the views of most public health experts at the time. Throughout the pandemic, Trump made false claims about the virus and pushed remedies that didn't work.
Motta traces a direct line from Trump's comments five years ago to public opinion trends that persist to this day. "It's the efforts that President Trump made to portray COVID-19 as not being that serious that led to polarization," Motta said.
A partisan split on vaccines
Attitudes about vaccines are one of the key ways that polarization has played out.
"Why would you vaccinate if the infectious disease threat isn't all that serious?" Motta said. "That's when we started to see a split in public opinion, such that Republicans came to hold more negative views toward vaccinating and Democrats came to hold more positive views."
The pandemic accelerated what had been an emerging trend of vaccine hesitancy becoming a more Republican issue, Motta said.
Those with negative views toward COVID-19 vaccines are increasingly negative about other vaccines too, research by Motta and others has found.
One in four Republican parents is now skipping or delaying some childhood vaccines for their kids, such as the MMR vaccine that protects against measles, according to a study from KFF, a nonprofit health policy organization.
"Now we have a political party that has a big chunk of its base being people with anti-vax views," said Joseph Uscinski, a political scientist at the University of Miami.
"And now you have political leaders pushing a lot of anti-vax ideas and making them very salient by putting people who push those ideas into major offices in our country's government," he said.
Several factors have driven the trend.
University of Washington biologist Carl Bergstrom, who studies the spread of infectious diseases and misinformation, calls the COVID-19 pandemic "a big opportunity for people pushing anti-vax propaganda to get their foot in the door with new segments of the population."
One of the most prominent spreaders of misleading content about vaccines was Robert F. Kennedy Jr., who formerly led Children's Health Defense, an anti-vaccination nonprofit, and is now Trump's secretary of health and human services.
In his new role, Kennedy has said a commission will investigate the childhood vaccination schedule, even though he had promised a U.S. senator that he would not change it. His agency recently tapped a vaccine skeptic who has previously spread false claims to reexamine the discredited theory that vaccines cause autism. He has made some statements promoting the use of MMR vaccines to address the measles outbreak, while also making other misleading and unsupported claims about the vaccine and emphasizing nutrition and alternative therapies like vitamin A instead. Following that advice, some children with measles in West Texas are being treated for toxic levels of vitamin A.
The top vaccine expert at the Food and Drug Administration, Dr. Peter Marks, was forced out of the agency and resigned Friday. "It has become clear that truth and transparency are not desired by the Secretary, but rather he wishes subservient confirmation of his misinformation and lies," Marks wrote.
Rethinking vaccine messaging
Public health experts are now taking a hard look back at how messaging about COVID-19 vaccines fell short.
Dr. Anna Durbin, a vaccine expert at Johns Hopkins Bloomberg School of Public Health, said the COVID-19 vaccines were designed to prevent death and severe illness — not to prevent infections entirely.
But she says that this wasn't well communicated, so many people mistakenly thought "they were never going to get COVID again — and we know that that's just not right."
Dan Salmon, the director of the Institute for Vaccine Safety at Johns Hopkins, said that in his view the Biden administration's decision to mandate that large employers require their staff to get COVID-19 shots or test weekly "backfired in a lot of ways." The rule was ultimately overturned by the U.S. Supreme Court.
"I don't think it improved vaccine coverage, but I think it made a lot of people feel like 'the government is making me do this,' and people don't like that," Salmon said.
A consequence of declining childhood vaccination rates is the growing number of measles cases in the U.S., most of which are linked to an outbreak that began in Texas in January.
"There's very real concern that this could result in widespread outbreak of measles," Salmon said. "I mean, I really hope that doesn't happen, but the U.S. is quite vulnerable right now."
Salmon said moving forward, effective vaccine messaging should recognize that patients and parents have legitimate questions they want answers to about vaccine safety.
"What we need to do in public health is address that concern and not name-call and not call the person anti-vaccine or anti-public health," Salmon said.
Vaccine research under threat
There's some irony to the partisan divide on vaccines. Some COVID-19 vaccines benefited from Trump administration initiatives, such as Operation Warp Speed, which accelerated vaccine development. The vaccines became widely available in 2021, once Trump was no longer in office, and he recommended that people get the shots, while also noting that people had the freedom to decide.
"The COVID vaccine saved millions of lives — it was remarkably successful. It was developed in a tiny fraction of the time of any previous vaccine," said Bergstrom.
But that success would likely be harder to replicate in the current political environment, even as bird flu looms as a potential health threat.
In recent weeks, federal health agencies have made mass layoffs and budget cuts, including eliminating funding for research on vaccine hesitancy. Scientists fear that research on mRNA technology, which was used in the leading COVID-19 vaccines, could be next.
Kennedy, the nation's top health official, has previously made negative statements about bird flu vaccines that vaccine experts have called false and inaccurate.
More recently, he made heterodox suggestions that poultry farms should consider no longer culling infected chickens, but scientists have raised alarms that such a plan could allow the virus to mutate in dangerous ways. His spokesperson defended the proposal to The New York Times as a way to protect humans from getting infected from sick chickens.
Motta, of Boston University, said he is concerned that elected officials are continuing to politicize public health issues.
"I'm really, really worried that we haven't learned our lesson from COVID-19."
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