March 14, 2024 – Just over 2 months into 2024, measles cases in the United States aren't looking great.
The recent rise in cases across the U.S. is linked to unvaccinated travelers, lower than ideal vaccination rates, and misinformation, experts said.
The CDC has identified 45 cases of measles in 17 jurisdictions across the U.S. As of March 7, the federal health agency reported measles cases in Arizona, California, Florida, Georgia, Illinois, Indiana, Louisiana, Maryland, Michigan, Minnesota, Missouri, New Jersey, New York City, Ohio, Pennsylvania, Virginia, and Washington.
As for the 45 cases, “that's almost as many as we had for the entire calendar year of 2023,” said Sarah Lim, MD, a medical specialist at the Minnesota Department of Health. “So we're really not off to a great start.” (For context, there were 58 officially reported measles cases last year.)
Chicago is having a measles outbreak this week – with eight cases reported so far. All but one case has been linked to a migrant child at a city shelter. Given the potential for rapid spread – measles is relatively rare here but potentially very serious – the CDC sent a team of experts to investigate and to help keep this outbreak from growing further.
Sometimes Deadly
About 30% of children have measles symptoms and about 25% end up hospitalized. Complications include diarrhea, a whole-body rash, ear infections that can lead to permanent deafness, and pneumonia. Pneumonia with measles can be so serious that 1 in 20 affected children die. Measles can also cause inflammation of the brain called encephalitis in about 1 in 1,000 children, sometimes causing epilepsy or permanent brain damage.
Similar to long COVID, some effects can last beyond the early infection. For example, measles “can wipe out immune memory that protects you against other bacterial and viral pathogens,” Lim said at a media briefing sponsored by the Infectious Diseases Society of America. This vulnerability to other infections can last up to 3 years after the early infection, she noted.
Overall, measles kills between 1 and 3 people infected per thousand, mostly children.
Vaccine Misinformation Playing a Role
Vaccine misinformation is partly behind the uptick, and while many cases are mild, "this can be a devastating disease,” said Joshua Barocas, MD, an associate professor of medicine in the divisions of General Internal Medicine and Infectious Diseases at the University of Colorado School of Medicine.
“I'm a parent myself. Parents are flooded with tons of information, some of that time being misinformation,” he said at the media briefing. “If you are a parent who's been on the fence [about vaccination], now is the time, given the outbreak potential and the outbreaks that we’re seeing.”
Vaccine misinformation “is about as old as vaccines themselves,” Lim said. Concerns about the MMR vaccine, which includes measles protection, are not new.
“It does seem to change periodically – new things bubble up, new ideas bubble up, and the problem is that it is like the old saying that ‘a lie can get halfway around the world before the truth can get its boots on.’” Social media helps to amplify vaccine misinformation, she said.
“You don't want to scare people unnecessarily – but reminding people what these childhood diseases really look like and what they do is incredibly important,” Lim said. “It's so much easier to see stories about potential side effects of vaccines than it is to see stories about parents whose children were in intensive care for 2 weeks with pneumonia because of a severe case of measles.”
Barocas said misinformation is sometimes deliberate, sometimes not. Regardless, “our job as infectious disease physicians and public health professionals is not necessarily to put the counternarrative out there, but to continue to advocate for what we know works based on the best science and the best evidence.”
“And there is no reason to believe that vaccines are anything but helpful when it comes to preventing measles,” he noted.
Lifelong Protection in Most Cases
The MMR vaccine, typically given as two doses in childhood, offers 93% and then 97% protection against the highly contagious virus. During the 2022-to-2023 school year, the measles vaccination rate among kindergarten children nationwide was 92%. That sounds like a high rate, Lim said, “but because measles is so contagious, vaccination rates need to be 95% or higher to contain transmission.”
One person with measles can infect anywhere from 12 to 18 other people, she said. When an infected person coughs or sneezes, tiny droplets spread through the air. “And if someone is unvaccinated and exposed, nine times out of 10, that person will go on to develop the disease.” She said given the high transmission rate, measles often spreads within families to infect multiple children.
If you know you’re not vaccinated but exposed, the advice is to get the measles shot as quickly as possible. “There is a recommendation to receive the MMR vaccine within 72 hours as post-exposure prophylaxis,” Lim said. “That's a tight time window, but if you can do that, it reduces the risk of developing measles significantly.”
If you’re unsure or do not remember getting vaccinated against measles as a young child, your health care provider may be able to search state registries for an answer. If that doesn't work, getting revaccinated with the MMR vaccine as an adult is an option. “There is no shame in getting caught up now,” Barocas said.
Lim agreed. “There is really no downside to getting additional doses.”