Measles Outbreak Fuels Vaccine Misinformation as Americans Face Uncertainty

As measles cases surge to 800 across multiple states this year, a new KFF Tracking Poll reveals widespread uncertainty among Americans about vaccine safety and measles misinformation. The survey shows most adults and parents have encountered at least one false claim about measles, with many unsure what information to believe.

The poll assessed public awareness and belief in three false statements circulating during the current outbreak, some of which have been amplified by Health and Human Services Secretary Robert F. Kennedy Jr. These include claims that MMR vaccines cause autism, that the measles vaccine is more dangerous than the disease itself, and that vitamin A prevents measles infections.

While fewer than 5% of adults consider any of these claims “definitely true,” the concerning finding is that fewer than half label them as “definitely false.” This leaves at least half of Americans expressing some uncertainty about each claim, describing them as either “probably true” or “probably false.”

Of the three falsehoods, the purported link between MMR vaccines and autism is most pervasive, with 63% of adults and 61% of parents reporting they’ve heard this claim. A third of both groups say they’ve encountered the false assertion that the vaccine is more dangerous than measles itself—a significant 15 percentage point increase since March 2024. The vitamin A prevention claim has reached about one-fifth of adults and parents.

Despite widespread scientific consensus rejecting these claims, a quarter of adults (25%) and a third of parents (33%) believe it’s “definitely” or “probably” true that MMR vaccines and autism are linked. The real-world impact of such beliefs is evident in vaccination decisions: 24% of parents who believe at least one of the false claims report delaying or skipping recommended childhood vaccinations—more than double the rate among parents who reject all three claims (11%).

The poll reveals significant partisan divides in vaccine confidence. While large majorities of adults (83%) and parents (78%) express confidence in MMR vaccine safety, this trust is much higher among Democrats (96%) and Democratic-leaning parents (95%) compared to Republicans (79%) and Republican-leaning parents (69%). Nearly one-third of Republican-leaning parents (31%) explicitly say they lack confidence in the vaccines’ safety.

Awareness of the current outbreak also follows partisan lines. Overall, about half of Americans (51%) express concern about the ongoing measles outbreak, with worry highest among Democrats (76%), Hispanic adults (62%), and Black adults (61%). While most adults (56%) and about half of parents (48%) recognize that measles cases have increased compared to recent years, Democrats and Democratic-leaning parents are significantly more likely to be aware of this trend than their Republican counterparts.

The findings come at a critical time as public health officials work to contain the measles outbreak. Measles was declared eliminated in the United States in 2000, but vaccine hesitancy and declining immunization rates have contributed to periodic outbreaks in recent years. The current spike in cases represents one of the more significant resurgences of the disease, which can cause severe complications including pneumonia, encephalitis, and death, particularly in young children.

Public health experts emphasize that the MMR vaccine has been extensively studied and repeatedly found to be safe and effective, with no scientific evidence linking it to autism. The benefits of vaccination far outweigh the minimal risks of side effects, which are typically mild and temporary.

The KFF survey was conducted between April 8-15, 2025, with a nationally representative sample of 1,380 U.S. adults in both English and Spanish. The margin of sampling error is plus or minus 3 percentage points for the full sample, with potentially higher margins for subgroups.