In the first three months of 2025, the U.S. had more measles cases than in all of 2024.

Measles outbreaks continue to spread in Texas, New Mexico, Kansas, Oklahoma, Ohio, according to the Centers for Disease Control. Cases have also been reported in Alaska, California, Colorado, Florida, Georgia, Kentucky, Maryland, Michigan, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island, Tennessee, Vermont and Washington.

A SciLine briefing in March included: Dr. Tina Tan, professor of pediatrics at the Feinberg School of Medicine of Northwestern University; Dr. Amy Winter, an assistant professor at the University of Georgia and the Department of Epidemiology and Biostatistics; and, Dr, David Higgins, practicing pediatrician and a health services researcher at the University of Colorado Anschutz Medical Campus. 

Measles is highly contagious. The virus can stay in the air for up to two hours after the infected person leaves the room. According to health officials, the measles vaccine is the only way to prevent and protect individuals against measles.

Thanks to widespread vaccination, the United States eliminated measles as of the year 2000. Elimination status requires are no transmissions for 12 months or more.

However, in recent years, due to widespread misinformation about vaccines, the U.S. again has experienced outbreaks of the virus.

“Humans are the only natural host of the measles virus, and persons of all ages can be infected, with the persons at the highest risk for developing severe disease being those that are too young to be vaccinated and those that are unvaccinated,” explained Dr. Tan.

“A measles infection starts with symptoms of fever, cough, runny nose, and redness of the whites of the eyes, known as conjunctivitis, that is followed three to five days later by the development of a red blotchy rash that begins on the face, usually around the hairline, and then spreads down the body and out toward the arms and legs,” she continued. “Persons are contagious from four days prior to the appearance of the rash through four days after the appearance of the rash, with immunocompromised patients staying contagious for a longer period of time.

“One thing about measles that makes it so serious is it is the most highly transmissible infection that a person can get. A person with measles can transmit the disease to as many as 18 other susceptible individuals with transmission in a household setting of 90% or higher. Infection also places a person at risk for severe complications like pneumonia, encephalitis, which is the brain swelling, with neurologic deficits and seizures. You can get permanent deafness, you can get permanent blindness, and you can die from the disease. And we also know that the infection significantly weakens a person’s immune system, which places them at very high risk for other potentially serious infections,” Dr. Tan added.

“Measles vaccine is safe, it’s effective. With one dose, it’s just 93% effective, and with two doses, it’s 97% effective. In fact, it’s also believed to offer lifelong immunity from disease,” said Dr. Winter.

“The MMR vaccine, which protects against measles in addition to mumps and rubella, is typically given in two doses. The first, as a pediatrician, I give to patients at 12 to 15 months old and the second around four to six years old,” said Dr. Higgins.

“There are patients who either cannot get the vaccine or for whom when they get the vaccine, it doesn’t give that protection that we hope it would. This includes people like infants, those with weakened immune systems, people who have cancer and are immune compromised,” he added. “When vaccination rates drop in a community, it is not a question of if, it’s a question of when measles is going to come because it is so incredibly contagious.

Dr. Higgins noted that recent some reports about using Vitamin A to lessen measles symptoms have been misleading. “Vitamin A does not prevent measles and it is not a substitute for vaccination,” he explained.  Vitamin A can play a role in reducing the severity of symptoms, especially in people who are Vitamin A deficient, he added.

“The MMR vaccine is incredibly safe. Decades of research confirming that it is incredibly safe,” Dr. Higgins said. “Like all vaccines, it can cause mild temporary side effects. A low-grade fever, it can cause a rash, soreness at the injection site. And serious side effects are extremely rare. What you will see in the headlines and what we’re all hearing a lot about right now is the MMR autism myth. This gained mainstream attention in the late 1990s after a fraudulent study was published. And this has been thoroughly disproven by numerous, dozens of large-scale studies, including millions of children. There is no link between the MMR vaccine and autism or other long-term health issues. It is a very safe vaccine.”

Dr, Higgins said the risk of measles transmission is just “one plane flight away” for any American who is unvaccinated. “If an American who is unvaccinated goes and travels to one of these countries where anywhere in the world where measles has increased, they bring it back,” he said. The virus can also be brought in by foreign travelers.

Dr. Winter pointed out that in 2019, 63% of cases of measles in the U.S. were directly linked to unvaccinated U.S. citizens who traveled outside the country and brought back the virus. She said school classrooms are still the primary conduit of mass infections, so focusing on vaccinating children before they enter school is important.

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