• Posted April 23, 2026

ER Study Finds Major Gaps in Measles Immunity

As measles cases in California hit a seven-year high, new research suggests many adults are walking around without the protection they need.

A nationwide study reveals that emergency departments are seeing a high volume of patients who are under-vaccinated, uninformed or hesitant about the measles-mumps-rubella (MMR) vaccine.

Measles is notoriously easy to spread through simple actions like coughing or sneezing. Because it is so contagious, even a tiny dip in community vaccination rates can trigger a massive outbreak.

The study — publishing in the July issue of The American Journal of Emergency Medicine — looked at survey data from nearly 2,500 adults across 10 U.S. emergency departments to see who is falling through the cracks.

The survey, which ran from mid-April 2024 until Dec. 31, 2024, included eight U.S. cities (Chicago, Detroit, Los Angeles, Philadelphia and San Francisco, as well as Fresno and Sylmar, both in California; and Durham, North Carolina).

The findings were eye-opening for public health officials. 

About 25% respondents had never heard of the MMR vaccine, and 44% were not up to date on their shots. This lack of awareness often leads to vaccine hesitancy, where people avoid the shot due to myths about its safety.

“We found that a substantial portion of emergency department patients lack accurate knowledge about measles and the MMR vaccine,” co-lead author Alexandra Eftimie, a medical student at the University of California - Riverside (UCR), said in a news release. “Many participants were either unsure of their vaccination status or reported not receiving the vaccine at all.”

Researchers found that the gaps weren't random. Specific groups were much more likely to be unvaccinated due issues such as limited insurance, language barriers or a lack of a regular family doctor.

African-American and Hispanic patients, men and non-English speakers were less likely than others to be unvaccinated, the study showed.

“These disparities specifically emphasized how systemic barriers shape both access to vaccines and health literacy among diverse populations,” said co-lead author Sahithi Malireddy, a medical student at UCR.

Among those who were not up to date on the measles vaccination, 36.5% were willing to receive it if offered in the ED, the study found.

While most emergency rooms aren’t designed for routine shots, the research suggests ERs are perfectly positioned to act as a safety net. For many marginalized people, a visit to the ER is the only time they interact with the health care system.

Senior author Dr. Robert Rodriguez, associate dean for clinical research at UCR, noted that while ERs might not always give the shot on the spot, they can play a huge role in screening. 

“They can inform patients about the importance of the MMR vaccine and direct them to accessible options, such as clinics and pharmacies, where they can receive it,” he said.

Without a centralized U.S. vaccine database, researchers relied on self-reported information for the vaccine status of each participant.

More information

Learn how to protect yourself from measles at the U.S. Centers for Disease Control.

SOURCES: University of California – Riverside, news release, April 17, 2026; The American Journal of Emergency Medicine, July 2026