Benefits of MMR vaccine for children outweigh risks by nearly 5-1, reports research

The United States is in the midst of the second-highest year of measles cases since 2000, when the disease was declared eliminated in this country, meaning that cases within the United States originated outside the country. As of May 8, the U.S. Centers for Disease Control and Prevention (CDC) reported that in 2025, there have been over a thousand confirmed U.S. cases of measles and three confirmed deaths from measles. Because many cases go unreported, this number is considered an undercount. In contrast to the current outbreak, from the time the United States declared that measles was no longer endemic through last year (2000-2024), there’s been an average of about 180 measles cases a year.

While many Americans know how measles can spread, most cannot accurately estimate the prevalence of complications associated with measles such as hospitalization or the risks it presents during pregnancy, according to the latest Annenberg Science and Public Health (ASAPH) survey, which was conducted among 1,653 empaneled U.S. adults from April 15-28, 2025, by the Annenberg Public Policy Center (APPC) of the University of Pennsylvania.

The survey finds that more than 8 in 10 Americans (83%) are not worried that they or someone in their family will contract measles over the next three months. “Since the overwhelming number of individuals in this country, including children, either have had measles or have been vaccinated against it, it is unsurprising that few are worried about getting the virus,” said Kathleen Hall Jamieson, director of the Annenberg Public Policy Center and of the survey. “But with measles cases reported in 31 states and vaccination rates dropping, everyone should be knowledgeable about the symptoms, treatment, and the prevention of measles through the highly effective MMR (measles, mumps, and rubella) vaccine.”

The two doses of the measles vaccine – which are recommended at ages 12-to-15 months for the first dose and 4 to 6 years old for the second dose – are 97% effective at preventing measles among those who are vaccinated and exposed to it, the CDC reports.

Highlights

The Annenberg Public Policy Center’s April 2025 health survey finds that:

• Two-thirds of U.S. adults (67%) know that it’s false to say vaccines given to children, like the MMR (measles, mumps, and rubella vaccine), cause autism – but the number who know this is false declined significantly, from 74% in 2021.
• Americans overwhelmingly say the benefits of the MMR vaccine for children outweigh the risks (83% to 17%).
• Many more Americans (70%) think healthy children should be required to be vaccinated to attend public school because of the potential risk to others who are not vaccinated than think it should be a matter of parental choice (18%).
• Most Americans know the most common ways measles can be spread, but about half are not sure how common complications are – or what the risks are during pregnancy.

Preventing measles with the MMR vaccine

Although decades of research have established that the childhood vaccine for measles, mumps, and rubella (MMR) is the best way to protect against measles, some parents are hesitant to have their children vaccinated, in part because of the debunked claim that the MMR vaccine can cause autism. Two-thirds of Americans (67%) say the purported link between MMR and autism is a false one. While the proportion who say the MMR vaccine does not cause autism is sizeable, it is significantly lower than the 74% who said so in June 2021, when the ASAPH survey first asked this question. In the current survey, 1 in 7 people (14%) say it is true that the MMR vaccine causes autism, an increase of 5 percentage points from June 2021 (9%).

To most Americans, the benefits of the MMR vaccine for children outweigh the risks by a wide margin (83% vs. 17%). However, the percentage of Americans who believe the benefits outweigh the risks has dropped slightly but significantly from August 2023, when 89% said the benefits outweighed the risks. Further, 81% say it is true that medical professionals recommend that those who are able to be safely vaccinated take the MMR vaccine even if their chances of exposure are low. This proportion is significantly higher compared to April 2024, when 74% said this was true.

Most agree on vaccine requirements for children to attend public school

When asked about their views on MMR vaccine requirements for children attending school, vastly more people agree that healthy children should be required to be vaccinated to attend public school because of the potential risk to others who are not vaccinated (70%) than say parents should be able to decide, even if it creates risks for others (18%). These results show a significant uptick in support for school vaccine requirements in the 20 months since August 2023 (63%), and a significant decline among those supporting parental choice (22% in August 2023).

Measles risks during pregnancy not widely understood

For people who are pregnant and have not had the MMR vaccine, getting measles can lead to serious complications, such as delivering a low-birth weight baby and early delivery. When asked to select among a list of complications that could occur in someone with measles who is pregnant, a third of survey respondents correctly identify delivering a low birthweight baby (34%) or experiencing an early delivery (34%) as complications of having measles while pregnant. More people identify death as a possible complication this year (16%, significantly more than the 12% last year). A small number of people incorrectly indicate that diabetes (7%) and blurred vision (11%) are more likely to occur if you have measles while pregnant. They are not. Most Americans (57%) say they are not sure what the complications are.

The CDC recommends measles vaccination before but not during pregnancy for those who are unvaccinated; however, only 15% know this. The CDC notes: “Even though MMR is a safe and effective vaccine, there is a theoretical risk to the baby. This is because it is a live vaccine, meaning it contains a weakened version of the living viruses.” The CDC recommends the MMR vaccine be given a month or more before someone becomes pregnant, if that person was not already vaccinated against measles, mumps, and rubella.

Most know how measles spread, but few grasp risks

Amid the current measles outbreak, nearly 6 in 10 (58%) say there are more measles cases in the U.S. than in the comparable period last year. More than a quarter (27%) indicate that they are not sure whether there are more cases than last year, 5% think there are fewer cases, and 11% say the number of cases is about the same.

More people know how measles spreads: Most Americans can identify common ways measles spreads. Two-thirds (66%) correctly say that measles can be spread by touching a contaminated surface and then touching one’s nose, mouth, or eyes, a significant increase from last April when 59% indicated this as a means of spreading measles. Slightly fewer Americans (63%) correctly say that measles can be spread by coughing or sneezing, no statistical difference from last year.

Few know the measles incubation period: Very few of those surveyed know how long a person infected with measles can spread the virus before developing the signature measles rash. One in 7 (14%) correctly estimate that a person can spread the infection for four days before developing a rash, while 12% estimate that the period is one week. The majority of people (55%) report not being sure. These results are unchanged from April 2024.

Few accurately estimate symptoms and complications: Although a majority of respondents know common ways that measles can spread, about half of Americans express uncertainty about how often certain complications occur – and only a small percentage can accurately estimate them. Accuracy was determined for these symptoms if the respondent estimated the incidence within a range of ± 4 percentage points of the actual CDC incidence.

Respondents were asked to estimate the number of people who would experience specific symptoms and complications out of 100 people with measles.

• Hospitalization. The CDC reports that about 13% of people who got measles in 2025 were hospitalized, but just over 1 in 8 Americans (13%) estimate this incidence correctly. A third (33%) say they are not sure about the incidence and the remainder either overestimate (36%) or underestimate (17%) the incidence of those with measles who will become hospitalized. This represents no significant change from 2024.
• Diarrhea. According to the CDC, about 1 in 10 people who become infected with measles will experience diarrhea as a result. Fifty-four percent of Americans are not sure how many people out of 100 with measles would experience diarrhea, a significant increase in uncertainty of 6 percentage points since April 2024, when we last asked this question (48% unsure). Four percent estimate accurately, 33% overestimate the incidence (down significantly from 40% last year), and 7% underestimate the number.

Beliefs about non-vaccine treatments for measles

Visiting Texas during the measles outbreak in March of this year, U.S. Secretary of Health and Human Services Robert F. Kennedy Jr. said in a Fox News interview that doctors were getting positive results by treating measles with, among other things, cod liver oil, which contains “high concentrations of vitamin A and vitamin D.” Health experts grew concerned that the emphasis on vitamin A could be misheard to suggest that vitamin A could prevent the disease among those exposed to it. However, experts on infectious diseases emphasize that vitamin A cannot prevent someone from getting measles. And a recent New York Times story reports that Texas physicians treating measles patients say they have cared for “a handful of unvaccinated children who were given so much vitamin A that they had signs of liver damage.” (See our project FactCheck.org’s report on Kennedy’s recent, misleading statements about measles.)

The ASAPH survey asked about vitamin A and cod liver oil as a preventive measure against measles and found that a plurality says that taking a daily dose of vitamin A (46%) or a large amount of cod liver oil each day (47%) has no effect on whether one will get measles. An equal number are unsure about the effectiveness of each (45% and 48%, respectively). Just 9% say taking vitamin A daily helps protect one against getting measles and just 4% say taking large amounts of cod liver oil each day would do the same.

As for the general health benefits of taking a large amount of cod liver oil every day, 48% say they are unsure whether there are any health benefits or not. Just as many say cod liver oil improves a person’s health (16%) as say it harms (15%) one’s health. (A 2024 study suggests that fish oil supplements “might be a risk factor” among healthy people for atrial fibrillation and stroke.) A fifth (22%) say taking large amounts of cod liver oil every day has no effect on one’s health one way or the other.

The ASAPH survey

The survey data come from the 24th wave of a nationally representative panel of 1,653 U.S. adults, first empaneled in April 2021, conducted for the Annenberg Public Policy Center by SSRS, an independent market research company. This wave of the Annenberg Science and Public Health Knowledge (ASAPH) survey was fielded April 15-April 28, 2025. The margin of sampling error (MOE) is ± 3.4 percentage points at the 95% confidence level. All figures are rounded to the nearest whole number and may not add to 100%. Combined subcategories may not add to totals in the topline and text due to rounding.