Summary: A recent national survey found that 24% of U.S. adults mistakenly believe the MMR (measles, mumps, rubella) vaccine causes autism, despite clear guidance from the Centers for Disease Control and Prevention (CDC) that no such link exists. This persistent misconception is tied to growing vaccine hesitancy and coincides with a notable rise in measles cases.
The survey underscores the ongoing need for clearer, evidence-based public education about vaccine safety and the real risks posed by declining immunization rates.
Key Facts:
- 24% of U.S. adults incorrectly believe the MMR vaccine causes autism.
- Measles cases in the U.S. have risen sharply, with 146 confirmed cases in 2024 as of May 30.
- The CDC and decades of research confirm there is no link between the MMR vaccine and autism.
Source: University of Pennsylvania
Overview
As measles cases increase and MMR vaccination coverage declines, a new survey from the Annenberg Public Policy Center (APPC) at the University of Pennsylvania finds that roughly one in four American adults rejects the established scientific conclusion that the MMR vaccine does not cause autism. An additional 3% said they were unsure.
The CDC states there is no evidence linking the measles vaccine and autism. Nevertheless, the belief in a connection remains entrenched among a substantial portion of the public—reflecting the long-term impact of discredited claims that originated in a 1998 Lancet paper later retracted.
APPC’s April 18–24, 2024 survey of more than 1,500 U.S. adults shows continuity with earlier findings: sizeable shares of the public either accept the false claim that MMR causes autism or are unsure. Similar patterns were recorded in APPC and NORC surveys before and during the COVID-19 pandemic, indicating the belief has been persistent for years.
“The persistent false belief that the MMR vaccine causes autism continues to be problematic, especially given the recent rise in measles cases,” said Kathleen Hall Jamieson, director of the Annenberg Public Policy Center. APPC research also ties this misconception not only to reluctance about the measles vaccine but to broader vaccine hesitancy.
The growth in measles cases
The CDC reports increasing measles activity both globally and in the United States. By May 30, 2024, health authorities had confirmed 146 U.S. cases across 21 jurisdictions, including 11 outbreaks involving three or more linked cases. From January 1, 2020, through March 28, 2024, the CDC recorded 338 confirmed cases, with nearly a third of those (97 cases) occurring in the first quarter of 2024—a dramatic rise compared with previous years.
Children are particularly affected: the median age of patients in these cases was three years. Most infections occurred in people who were unvaccinated or whose vaccination status was unknown. Public health experts have linked part of the increase to declines in childhood vaccination coverage during the COVID-19 pandemic.
Measles knowledge
How Measles Spreads
Most respondents correctly identified common routes of measles transmission: about 59% said measles can spread through coughing and sneezing, and a similar share recognized surface-to-face contact as a potential route. However, more than one in five people (22%) mistakenly believed measles can be transmitted through unprotected sexual contact, underscoring gaps in basic awareness about how the virus spreads.
Measles Incubation Period
Awareness of the measles incubation period and infectious window is limited. Only 12% correctly estimated that a person can spread measles up to four days before the characteristic rash appears; another 12% guessed a one-week period. A majority—55%—said they were not sure.
Measles complications for pregnant people
Survey participants were asked which complications are associated with contracting measles during pregnancy. Fewer than 40% correctly identified two known risks: delivering a low-birth-weight baby (38%) and preterm delivery (37%). Small percentages mistakenly believed that diabetes (7%), blurred vision (11%), or death (12%) are direct, increased risks tied specifically to measles in pregnancy.
Measles vaccination (MMR) while pregnant
Most respondents (57%) were unsure whether pregnant people who have not been previously vaccinated should receive the MMR vaccine. Nearly a third (32%) incorrectly thought medical professionals recommend vaccinating during pregnancy, while only 12% correctly reported that health authorities do not advise MMR vaccination for pregnant individuals. The reason is that the MMR vaccine is a live, attenuated vaccine; although it is safe and effective for most people, public health guidance errs on the side of caution because of the theoretical risk to the fetus.
The CDC advises that people who need MMR protection should receive the vaccine at least one month before becoming pregnant if they were not immunized as children.
APPC’s ASAPH survey
These findings come from the 19th wave of the Annenberg Science and Public Health Knowledge (ASAPH) survey, a nationally representative panel of 1,522 U.S. adults first empaneled in April 2021. Fielded April 18–24, 2024 by SSRS for the Annenberg Public Policy Center, this wave has a margin of sampling error of ±3.5 percentage points at the 95% confidence level. Figures are rounded and may not total 100% due to rounding.
APPC has been tracking public knowledge, beliefs, and behaviors about vaccination, COVID-19, flu, maternal health, climate, and other public health topics for several years. The survey team for this wave included Kathleen Hall Jamieson, Shawn Patterson (data analyst), Patrick E. Jamieson (question developer), and Ken Winneg (survey fielding supervisor).
About this reporting
Author: Michael Rozansky
Source: University of Pennsylvania
Contact: Michael Rozansky – University of Pennsylvania
Image: The image is credited to Neuroscience News