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MMR vaccine medical misinformation still prevalent

Medical misinformation about the MMR vaccine comes as measles cases are on the rise in the U.S., experts say.

Medical misinformation about the MMR vaccine is still rampant, with a new survey from the Annenberg Public Policy Center (APPC) showing that a quarter of Americans do not accept scientific evidence that there's no link between the shots and autism.

While 24% of the 1,522 U.S. adults surveyed said they believe the CDC's statement that the MMR vaccine, which protects against measles, mumps and rubella, does not cause autism, another 3% said they are not sure.

"The persistent false belief that the MMR vaccine causes autism continues to be problematic, especially in light of the recent increase in measles cases," said Kathleen Hall Jamieson, director of the Annenberg Public Policy Center, in a press release. "Our studies on vaccination consistently show that the belief that the MMR vaccine causes autism is associated not simply with reluctance to take the measles vaccine but with vaccine hesitancy in general."

These findings come amid a wave of new measles cases nationwide.

Per CDC figures, there were 338 new confirmed measles cases between January 1, 2020, and March 28, 2024, a third of which occurred during the first quarter of 2024. That's a 17-fold increase over the mean number of cases reported in the first quarters of 2020 through 2023.

CDC said most of the cases were among patients who were unvaccinated or whose vaccination status was unknown.

While patients may decline to receive certain vaccinations for various reasons, vaccine hesitancy driven by medical misinformation is a key factor, and the APPC survey shows misinformation is still common.

According to the survey, fewer than half (41%) of respondents fully agreed with the CDC statement clarifying no connection between the MMR vaccine and autism. Another 32 percent said it was somewhat accurate.

Public sentiment about the MMR vaccine is mostly unchanged from October 2018, when 24% of respondents said the CDC statement was at least somewhat inaccurate. In that survey, 37% said the CDC statement was somewhat accurate, and 35% percent said it was very accurate.

Public knowledge of measles is varied

It's not just limited knowledge about MMR vaccine safety that's pervasive, the survey showed. Public knowledge about measles as an illness, between its spread and its incubation period, is variable.

For example, only six in 10 respondents could correctly state that measles can be spread through coughing and sneezing and by touching a contaminated surface and then touching one's nose, mouth or eyes. However, about a fifth of survey respondents incorrectly identified unprotected sexual contact as a way measles spreads.

What's more, respondents admitted to being unsure of the measles incubation period, or how long a person who is infected can spread the disease before developing a measles rash.

More than half (55%) said they were unsure of the measles incubation period. Only 12% correctly stated that an individual can spread measles for four days before developing a rash.

MMR recommendations in pregnancy unclear

The survey revealed a particular blind spot regarding MMR vaccination while pregnant, as well as the risks of contracting measles while pregnant.

Around four in 10 respondents correctly identified low baby weight (38%) and early delivery (37%) as potential birthing complications resulting from perinatal measles.

A smaller proportion incorrectly identified diabetes (7%), blurred vision (11%) and death (12%) as complications should a pregnant person contract measles. However, experts say those are not likely to occur.

Respondents were also unsure about MMR vaccination recommendations during pregnancy, with 57% reporting as much. About a third (32%) incorrectly said healthcare providers would recommend an unvaccinated, pregnant person to get the MMR vaccine. Only 12% correctly identified that a pregnant person should not get the MMR vaccine due to its use of a weakened, live form of the virus.

Although the MMR virus is safe and effective, use of the weakened, live virus could pose a "theoretical risk" to the baby, the CDC says.

Sara Heath has been covering news related to patient engagement and health equity since 2015.

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