The measles vaccination rate among kindergarten-age children in Missouri has dropped from 95% to approximately 90% since 2017, according to state health officials.
Most people in the country receive a measles vaccine as part of a two-dose regimen of the MMR shot — which also protects against mumps and rubella.
Epidemiologists say the declining rate, which mirrors a trend happening nationwide, could put the state’s young children at risk.
“Whenever we have a measles outbreak, the vast majority of people that are infected by measles are unvaccinated people,” said Lynelle Phillips, the board president of the Missouri Immunization Coalition. The more people who aren’t vaccinated, the more will likely get sick.
Measles has a long incubation time — weeks could go by before someone knows they’re sick, and someone can transmit it days before and after the onset of the telltale rash.
Most people who get sick first experience fever, fatigue and a stuffy nose. Sometimes white spots develop in an infected person’s throat. A few days after symptoms appear, a red rash will appear on a patient’s body. Usually a very high fever accompanies the rash, doctors said.
Measles can be serious and even fatal for young children, according to the Mayo Clinic. The disease for decades was rarely encountered in the United States as vaccination rates surged. But each year, the virus kills tens of thousands of people, most of them children outside the United States.
The virus is highly transmissible, Missouri Department of Health and Senior Services epidemiologist Nathan Koffarnus said. One infected person can cause an outbreak, especially if others aren’t vaccinated.
“Once it's introduced, it gets into a population that's not vaccinated, and then we get kind of this explosion of cases, " Koffarnus said. “If a person with measles were walking into a room with 10 other people who haven't been vaccinated, we would expect nine of those people to get measles as a result.”
Because of its contagious nature, even a small percentage change in vaccination rates can be significant in "making sure that this is only a case or two cases, instead of an outbreak,” he said.
The vaccine was introduced more than a half-century ago, and 99% of children who receive two doses are protected from the virus.
Federal officials say the 64 measles cases reported in the U.S. so far this year has exceeded the entire case count for 2023.
Missouri health officials have seen a few measles cases this year, Koffarnus said, but didn’t specify how many. Those cases were all in the same household.
When measles vaccination rates fall below 95%, the entire community has a loss of herd immunity, said Phillips of the Immunization Coalition.
She called the drop in vaccination rates tragic.
“It’s leaving us vulnerable as a state, and we really need to step up our efforts,” she said. “I am most concerned about the infants 12 months and younger, who aren't eligible to be vaccinated at this point and are sitting ducks.”
The coronavirus pandemic amplified skepticism of vaccines and also disrupted vaccine schedules because children weren’t in physical schools and weren’t going to the doctor as much, Phillips said.
Phillips and Koffarnus said there will always be people who don’t want their children vaccinated, and public health officials will likely not be able to change their minds. But many people just need more information or need to be reminded of how important immunizations are.
“We can't can't stop people from sharing misinformation,” Koffarnus said. “But what we can do is try to make the real information as available as user friendly and easy to understand as possible.”
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