The 17% of surveyed respondents who believe the harms of the vaccine outweigh the benefits were also significantly more likely to seek out health information from non-authoritative sources. These include social media influencers, alternative health practitioners or alternative health newsletters, such as the one produced by Children’s Health Defense, an anti-vaccine advocacy group founded by now-health Secretary Robert F. Kennedy Jr.

In contrast, for the vast majority who see vaccines as a positive, these sites are essentially shunned.

“My main takeaway isn’t so much where the hesitant people are online, but where the non- hesitant people are not online,” said Lauren Gardner, senior author of the paper and a Johns Hopkins professor in the Department of Civil and Systems Engineering. “What we saw is that everyone is really online, but people that are more likely to be supportive of vaccines are very selectively not using some of those new right, fringy media outlets.”

The survey was done in August 2025 during the worst year for measles outbreaks in the U.S. in decades, with 2,288 confirmed cases and three deaths, two of them unvaccinated children. During this period of time, the survey showed that those who were vaccine hesitant were consuming far more information and engaging with far more media than those who supported immunization, she said. 

“More information is better until the information sources become really unreliable, and potentially harmful,” Gardner said. “In which case, more information is not better. It’s confusing, it’s misleading, (it’s) misguiding.”

The researchers surveyed nearly 3,000 U.S.-based adults via an online panel survey. They noted that while previous work has tended to zero in on the singular moment in which adults choose to vaccinate themselves or their children, they decided to focus on the larger world of vaccine hesitancy, including the shifting attitudes and beliefs people hold. Participants were deemed vaccine hesitant if they indicated a belief that the harms of vaccines outweigh the benefits.

The authors of the study — research scientist Amelia Jamison, Ph.D. candidate Samee Saiye and Gardner — set out to better understand the relationship between individuals’ media consumption and their views around the MMR vaccine. 

Of those reported sickened in the 2025 outbreaks, some 93% were unvaccinated or their status was unknown and 70% of them were kids. Just four months into 2026, nearly cases have been reported across 36 states.

These outbreaks followed precipitous declines in childhood vaccination rates, which have been falling since the COVID pandemic. Last June, Gardner and Saiyed published showing that rates had dropped in 78% of the more than 2,000 counties they studied across 33 states, and that the average immunization rate had fallen to 91% — further below the 95% threshold needed for herd immunity.

Vaccine-hesitant adults in this latest study were more likely to identify with the Republican party (39%) or as independent voters (33%) and were much more likely to identify with the “Make America Healthy Again” movement (43%) than non-hesitant adults (26%). Consumption of legacy conservative media — such as Fox News or the New York Post — was not associated with vaccine hesitancy.

These skeptical adults also tended to skew younger and were more likely to be parents, racial minorities, lower income and less educated, but many of these demographics held less sway when researchers also considered types of media consumption. 

“Historically, demographics have been thought to be more of an explainer of attitudes,” said Gardner, “but in our work, we see that if you include those and then you also include media habits, the demographics really get overpowered and they no longer explain those vaccine attitudes. The better explanation is media habits.”

Researchers noted surprise at the sheer number of total respondents who reported being affiliated with MAHA: nearly 900, or 30%. The movement has proliferated in recent years and members have successfully used social media and other non-traditional outlets to around health and Kennedy’s political profile.

Gardner emphasized the strong caveat that this study was not causal, meaning it doesn’t demonstrate that vaccine hesitancy is a direct result of media consumption — just that there is a strong association. The team’s future research will explore if such a causal link exists and examine how these attitudes influence parents as they decide whether or not to vaccinate their young children — especially in light of shifting state policies around school-based compulsory vaccination.

The researchers found that consuming media from Breitbart, which they deemed a “new right” group, had a particularly marked association with vaccine hesitancy. Some of the theories promoted in such outlets have also been heard from top officials in the federal government, including Kennedy, who initially the measles spread in 2025 and has been in his support of the MMR vaccine since. 

Throughout his tenure as secretary, Kennedy has sown disruption, leading the charge to overturn a recommendation that all newborns receive the hepatitis B vaccine; change policies surrounding the combination MMR and varicella (chickenpox) vaccine; roll back recommendations around 2025’s COVID- 19 booster; and overhaul the U.S. childhood vaccine schedule, significantly reducing the number of shots routinely recommended for all kids. 

A preliminary injunction in March temporarily halted some of these changes, though the federal government filed an appeal , leaving the future of these policies uncertain.

When to take a stance on the vaccine at an April 22 Senate hearing, Kennedy responded, “We promote the measles vaccine,” adding that he has “always” said the injection is effective in 97% of people. 

This April, in a departure from previous top-level appointments, President Donald Trump nominated a , board-certified preventive medicine doctor, to head the Centers for Disease Control and Prevention, which falls under Kennedy’s Department of Health and Human Services. While some see this as a signal of shifting federal priorities, Kennedy said he Schwartz’s potential future vaccine policies at an April 21 U.S. House of Representatives hearing. 

Under Kennedy’s leadership, the Trump administration also released the controversial “Make America Healthy Again” in May 2025, which involved , misinterpreted studies, and is suspected of being generated in part .

Jamison, the research scientist who co-authored the Johns Hopkins study, said their work is particularly important given the current political climate in which public health has increasingly become front-page news.

“It used to be that if you were a parent you would seek out specific information when it became relevant for you,” Jamison said. “But now, when public health is so politically polarized post-COVID, and it’s so omnipresent across different news channels — being framed differently depending on which outlet — to me, that really spoke to the fact that people’s casual news consumption is probably contributing to their beliefs about vaccines, (and) not always in a super conscious way.”

Childhood vaccination rates have markedly declined across the U.S. since the start of COVID, according to new Johns Hopkins University showing 78% of more than 2,000 counties reported drops and the average immunization rate had fallen to 91% — further below the 95% threshold needed for herd immunity.

While existing Centers for Disease Control and Prevention data has historically shown broadly declining measles-mumps-rubella vaccination rates at the state and national levels, the county-level analysis published this week in JAMA is far more granular.

It provides a “better understanding of these pockets where you have more exceptionally high risk,” said senior author Lauren Gardner, the director of Johns Hopkins University’s Center for Systems Science and Engineering.

“Knowing where there are problem areas,” she added, “gives policymakers and public health professionals locations to target their limited resources to try and improve vaccination coverage and therefore minimize the potential risk of measles outbreaks.”

The country is currently experiencing a deadly measles outbreak that has infected over people across 30 states and killed two unvaccinated children. Case numbers this year have already surpassed 2024’s total and mark the second-highest number of confirmed cases in a year since the disease was declared eradicated in the U.S. in 2000. Some 96% of reported infections have involved a person who was unvaccinated or whose status was unknown and 13% have resulted in hospitalization.

Gardner, who also led the data collection efforts behind , and her team collected county-level, two-dose MMR vaccine rates for kindergarteners from each state’s department of health website from 2017 to 2024, where available. Ultimately, they were able to analyze trends in 2,066 counties across 33 states and made all their data available to download.

While state level average rates may decline by a few percentage points, the researchers found 130 counties where they dropped by at least 10 percentage points, and in 15 of those counties, they plummeted more than 20.

Only four of the states studied — California, Connecticut, Maine and New York — reported an increase in the median county-level vaccination rate. They are currently the only four states that exclusively allow medical — and not philosophical or religious — exemptions to mandatory vaccines for school-aged children.

Gardner said she pursued the county-level data after observing growing vaccine hesitancy and misinformation. Based on her years of work in the field, she said she was “100% expecting to see [these current outbreaks].” 

If vaccination rates continue to drop “measles is likely to return to endemic levels in the US,” according to the Johns Hopkins’ report — a concern other experts see as heightened by Robert F. Kennedy Jr. now heading the U.S. Department of Health & Human Services. A well-known vaccine skeptic, Kennedy initially the measles spread in late February and has been in his support of the MMR vaccine.

Under Kennedy’s leadership, the Trump administration released the controversial “Make America Healthy Again” on May 22, which misinterpreted studies, and is suspected of being generated in part . The report, which involved , questions the safety and importance of some childhood vaccines.

“Despite the growth of the childhood vaccine schedule,” the report reads, “there has been limited scientific inquiry into the links between vaccines and chronic disease, the impacts of vaccine injury, and conflicts of interest in the development of the vaccine schedule.” 

Paul Offit, the director of the Vaccine Education Center at the Children’s Hospital of Philadelphia and a professor of pediatrics at the University of Pennsylvania Perelman School of Medicine, pushed back on these assertions.

The issue has been well studied, and there is no evidence of links between childhood vaccines and chronic diseases — including diabetes and autism — said Offit, who is also member of the Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee.

He referenced 24 studies across seven countries and three continents involving thousands of children that show they’re at no greater risk of developing autism if they receive the MMR vaccine.

Current skepticism is not isolated to the measles vaccine: The Food and Drug Administration, which falls under HHS, recently released which no longer recommends the COVID vaccine for healthy children or pregnant women. In response, a top COVID vaccine adviser at the CDC resigned this week, according to reporting from  

And across the country, numerous states have introduced legislation to loosen vaccine requirements for school-aged children, opening the door for more parents to opt their kids out.

“I think this is only going to get worse,” Offit said. “I think vaccines are under attack. You have a secretary of Health and Human Services who will do everything he can during the years that he is in that position to make vaccines less available, less affordable and more feared. … So I think this is a dangerous time to be a child in the United States of America.”

Correction: In a previous version of this story, we incorrectly characterized Dr. Paul Offit’s status on the CDC’s Advisory Committee on Immunization Practices. He is a former voting member of the CDC’s advisory committee and a current member of the FDA’s vaccine advisory committee.