Measles Vaccines and Misinformation in the Courts: A Snapshot From the KFF Health Misinformation Tracking Poll

As part of KFF’s ongoing effort to identify and track the prevalence of health misinformation in the U.S., the latest KFF Health Misinformation Tracking Poll examines misinformation related to the measles vaccine and the public’s views of the U.S. government and social media companies’ role in moderating false claims online. This research builds on the Health Misinformation Tracking Poll Pilot, which found that adults across demographics were uncertain about the accuracy of many health-related false and inaccurate claims, such as the false claim that the measles, mumps, rubella (MMR) vaccine causes autism.

In 2000, measles was declared eliminated from the U.S. However, measles is now on the rise again with multiple states reporting cases this year including an outbreak in a Florida elementary school. Experts suggest this is largely the result of a decrease in childhood vaccinations due to missed vaccines during the COVID-19 pandemic from 2020 to 2022. Compounded with these circumstances, views and refusal of childhood vaccines have shifted and become more partisan over the course of the COVID-19 pandemic. While health misinformation and disinformation long preceded the pandemic, the pervasiveness of false and inaccurate information about COVID-19 and vaccines has renewed the focus on the role misinformation can play in distorting public health policy debates and impacting the health choices individuals make.

Misinformation About the Measles Vaccine

This KFF Health Misinformation Tracking Poll explores the prevalence and salience of one specific false claim related to the measles vaccine: “Getting the measles vaccine is more dangerous than becoming infected with measles.” Overall, most adults (82%) say they have not heard or read this claim, though one in six U.S. adults (18%) have heard or read it somewhere. Adults under age 30 – the group most likely to use social media for health information and advice – are most likely to report having heard this claim, though three in four (74%) in this age group have not heard it.

The survey also gauges whether people think this false claim is definitely true, probably true, probably false, or definitely false. Regardless of whether they have heard or read the claim, a fifth of adults (19%), including one quarter of parents, say this claim is “definitely” or “probably true.” Combining these measures, six percent of U.S. adults – including about one in ten (9%) parents of children under age 18 – say they have heard the claim and say it is definitely or probably true.

 

While most of the public correctly view the false claim that “The measles vaccine is more dangerous than the disease itself” as false, the findings echo previous KFF research showing that a majority express at least some uncertainty in their beliefs related to health claims. More than half of U.S. adults say this claim is either “probably false” (41%) or “probably true” (16%). Few (3%) say it is “definitely true” while four in ten (38%) are confident that the claim is “definitely false.”

Across partisans, levels of educational attainment, and race and ethnicity, fewer than five percent of adults say the claim is “definitely true,” meaning there are few ardent believers of this piece of misinformation. However, independents (37%) and Republicans (21%) are less likely than Democrats (59%) to be certain that the claim is “definitely false.” Those without a college degree (29%) are also less likely to say that the claim is definitely false than those with a college degree (55%).

While few adults say that this piece of misinformation is true, the public is split between saying it is “probably false” (41%) or “definitely false” (38%). Parents of children under age 18 are especially likely to say that this piece of information is “probably false” (50%). Having such a sizable group lean towards the correct answer, but be uncertain, may present an opportunity for intervention. Clear, accurate messaging from trusted sources, such as pediatricians, regarding the safety of the measles vaccine may solidify the public’s — and parents’ — correct inclination that the measles vaccine is not more dangerous than contracting the disease. This would allow parents to be more confident in their decisions when it comes to vaccinating their young children.

 

Social Media and Misinformation

The KFF Health Misinformation Tracking Poll Pilot found social media use is correlated with both exposure and inclination to believe health misinformation. While many adults reported frequently using social media, few said they would trust health information they may see on these platforms. However, those adults who frequently use social media to find health information and advice are more likely to believe that certain false statements about COVID-19 and reproductive health are true.

Building on that research, this KFF Health Misinformation Tracking Poll shows the public overall views the spread of health misinformation on social media as a bigger problem than the censorship of health speech on these platforms, with some divisions by partisanship. By more than a two to one margin, U.S. adults say, “people being allowed to say harmful or misleading things about health topics” (68%) is a bigger problem on social media than “people being prevented from sharing alternative viewpoints on health topics” (31%). Large shares of Democrats (85%) and independents (64%) say it is a bigger problem that people can say harmful things about health topics on social media, while Republicans are split with half (52%) saying the former is a larger problem and half (48%) saying the latter is a larger problem.

 

When asked about potential actions to prevent the spread of harmful and misleading health information on social media, a slightly larger share of the public supports action by social media companies rather than the U.S. government. This difference is largely driven by Republicans, as majorities of Democrats and independents are supportive of action by either social media companies or the U.S. government, but Republicans are more likely to be supportive of social media companies intervening as a solution for restricting false information.

About two thirds (66%) of adults overall say, “Social media companies should take steps to restrict false health information, even if it limits people from freely publishing or accessing information,” while one third instead say, “People’s freedom to publish and access health information should be protected, even if it means false information can also be published.” There are partisan differences on this question, but notably a large majority of Democrats (82%) along with smaller majorities of independents (57%) and Republicans (56%) agree that social media companies should act.

 

The public is more divided when asked about potential action by the U.S. government. About six in ten adults overall (57%) say, “The U.S. government should require social media companies to take steps to restrict false health information, even if it limits people from freely publishing or accessing information,” while about four in ten (42%) say, “People’s freedom to publish and access health information should be protected, even if it means false information can also be published.” Again, partisans divide, with a majority of Democrats (73%) and independents (60%) supportive of government intervention on this issue. Republicans (38%) are much less likely to say the U.S. government should intervene in this way.

 

This KFF Health Misinformation Tracking Poll was designed and analyzed by public opinion researchers at KFF. The survey was conducted February 20-28,2024, online and by telephone among a nationally representative sample of 1,316 U.S. adults in English (1,226) and in Spanish (90). The sample includes 1,036 adults (n=51 in Spanish) reached through the SSRS Opinion Panel either online (n=1,011) or over the phone (n=25). The SSRS Opinion Panel is a nationally representative probability-based panel where panel members are recruited randomly in one of two ways: (a) Through invitations mailed to respondents randomly sampled from an Address-Based Sample (ABS) provided by Marketing Systems Groups (MSG) through the U.S. Postal Service’s Computerized Delivery Sequence (CDS); (b) from a dual-frame random digit dial (RDD) sample provided by MSG. For the online panel component, invitations were sent to panel members by email followed by up to three reminder emails.

Another 280 (n=39 in Spanish) interviews were conducted from a random digit dial telephone sample of prepaid cell phone numbers obtained through MSG. Phone numbers used for the prepaid cell phone component were randomly generated from a cell phone sampling frame with disproportionate stratification aimed at reaching Hispanic and non-Hispanic Black respondents. Stratification was based on incidence of the race/ethnicity groups within each frame.

Respondents in the phone samples received a $15 incentive via a check received by mail, and web respondents received a $5 electronic gift card incentive (some harder-to-reach groups received a $10 electronic gift card). In order to ensure data quality, cases were removed if they failed two or more quality checks: (1) attention check questions in the online version of the questionnaire, (2) had over 30% item non-response, or (3) had a length less than one quarter of the mean length by mode. Based on this criterion, no cases were removed.

The combined cell phone and panel samples were weighted to match the sample’s demographics to the national U.S. adult population using data from the Census Bureau’s 2023 Current Population Survey (CPS), September 2021 Volunteering and Civic Life Supplement data from the CPS, and the 2023 KFF Benchmarking survey with ABS and prepaid cell phone samples. The demographic variables included in weighting for the general population sample are sex, age, education, race/ethnicity, region, civic engagement, frequency of internet use, political party identification by race/ethnicity, and education. The sample of registered voters was weighted separately to match the U.S. registered voter population using parameters above plus recalled vote in the 2020 presidential election by county quintiles grouped by Trump vote share. Both weights account for differences in the probability of selection for each sample type (prepaid cell phone and panel). This includes adjustment for the sample design and geographic stratification of the cell phone sample, within household probability of selection, and the design of the panel-recruitment procedure.

In addition, the sample of parents (n=283) includes adults from the SSRS opinion panel who say that they are a parent or guardian of a child 18 years or younger living in their home was weighted separately to the Census Bureau’s 2023 Current Population Survey (CPS) and the 2023 KFF Benchmarking survey. The demographic variables included in weighting for the parent sample are sex, age, education, race/ethnicity, and political party.

The margin of sampling error including the design effect for the full sample is plus or minus 3 percentage points and for registered voters is plus or minus 4 percentage points. Numbers of respondents and margins of sampling error for key subgroups are shown in the table below. For results based on other subgroups, the margin of sampling error may be higher. Sample sizes and margins of sampling error for other subgroups are available by request. Sampling error is only one of many potential sources of error and there may be other unmeasured error in this or any other public opinion poll. KFF public opinion and survey research is a charter member of the Transparency Initiative of the American Association for Public Opinion Research.