Measles vaccine exemption numbers in Boone County have jumped from 1% in 2020 to 2.6% in 2024, according to the Missouri Department of Health and Senior Services.
The statewide measles, mumps and rubella vaccine exemption rate is 5.2% as of 2024, an increase from 3.5% just a year prior, according to the department.
Measles is one the most contagious diseases in the world, spread by coughing, sneezing or rebreathing air that was breathed by someone with measles, according to the World Health Organization.
“I think it’s probably just part of the larger phenomena we’ve seen in society with overall vaccine hesitancy,” said Phillip Beck, an infectious disease specialist at Boone Health.
As of Monday, there have been no reported confirmed cases of measles in Boone County, according to the DHSS. In 2025, there have been confirmed measles cases in Cedar, New Madrid and Taney counties.
The most recent case, at St. Louis Lambert International Airport, was reported by the department on Feb. 17 in a news release.
“There’s been a handful of cases in Missouri, but none of those have been in Boone County,” Beck said. “But still in the next several years, (Boone County) has a potential to have cases and/or an outbreak, particularly in areas where a vaccination rate drops below the threshold for herd immunity.”
The herd immunity threshold is 95%; the state is currently at 90.14%, according to the DHSS website.
“The best way to prevent getting sick is to be immunized with two doses of a measles-containing vaccine, which is primarily administered as the combination measles-mumps-rubella or MMR vaccine,” according to release from the department. “Two doses of the MMR vaccine provide 97% protection from measles infections.”
There are two doses of the MMR vaccine that are administered at different times in a person’s life.
“The primary issue is in someone who’s not vaccinated or is under-vaccinated, where they only had one shot instead of two,” Beck said.
A person who is not vaccinated is at risk for contracting measles at any age, according to the DHSS measles fact sheet.
“If they are not immune, then the recommendation is to get the MMR vaccine within 72 hours of exposure and then quarantine for up to 21 days,” Beck said.
Measles symptoms
The symptoms of measles include cough, runny nose, red eyes, white spots in the mouth and a rash, according to the World Health Organization.
“The virus has a suppressive effect when people are sick early on inducing susceptibility to bacteria, you know, ear infection, pneumonia, and then the immune amnesia,” Beck said.
Beck explained immune amnesia is when a person’s immune system forgets immunization from previous vaccines and exposures which can last for several months or years.
Immune amnesia is not the only potential complication. According to the World Health Organization other complications can include blindness, an infection causing brain swelling and potentially brain damage, severe diarrhea, ear infections and breathing problems including from pneumonia.
The best way to prevent measles is to get vaccinated, Beck said.
