The phenomenon is known as immune amnesia, and it can leave people vulnerable to other infections for several weeks to months. Research has shown that it can take two to three years after a measles infection for protective immunity to fully return.

“The measles virus is strongly immunosuppressive, meaning that it will interfere with the normal function of many white cells in the body that fight against other infections,” Fennelly says.

One of those infections is bacterial pneumonia, which causes inflammation and fluid buildup in the lungs. About one in five people who get sick with measles in the US is hospitalized, and one in 20 will develop pneumonia. In some cases, patients may need supplemental oxygen or intubation and ventilator support.

In a February 28 press briefing, Ron Cook, chief health officer at the Texas Tech University Health Sciences Center in Lubbock, described the hospitalized patients as having severe symptoms, with many of them also experiencing dehydration and low oxygen levels due to inflammation in the lungs.

“Pneumonia is the most common cause of death for measles in young children,” says Edith Bracho-Sanchez, an assistant professor of pediatrics at Columbia University Vagelos College of Physicians and Surgeons.

Measles can also cause a severe complication called encephalitis, or swelling of the brain, which can be fatal. Encephalitis can happen during an infection if the virus travels to the brain, or after an infection if the brain becomes inflamed because of an overactive immune response. About one child out of every 1,000 who get measles will develop encephalitis. The condition can cause convulsions and in rare cases, deafness or intellectual disability.

The measles, mumps, and rubella (MMR) vaccine is the best way to protect against these complications. One dose of the vaccine is 93 percent effective against measles, and two doses is 97 percent effective. The first dose is recommended for children ages 12 to 15 months old, and the second dose is typically given between the ages of 4 and 6.

There are no antiviral treatments available for measles, and while vitamin A is often given to people with an infection, it does not prevent measles or kill the virus. “The infection itself can deplete levels of vitamin A in the body,” Bracho-Sanchez says. Both the World Health Organization and the American Academy of Pediatrics recommend two doses of vitamin A to children who are hospitalized with measles, since vitamin A deficiency can increase the risk of serious complications. However, large doses of vitamin A can be toxic.

Secretary of health and human services Robert F. Kennedy Jr. has suggested that treatment with cod liver oil, which contains vitamin A, is showing “very, very good results” in measles patients. But health experts caution that cod liver oil supplements can contain more vitamin A than the recommended daily amount and can also make children sick if they take too much.

Bracho-Sanchez says the best way to have adequate levels of vitamin A is to eat a diet rich in fruit and vegetables. Vaccination, she says, remains the best way to protect against measles.

Updated 3-11-2025 7:37 pm GMT: A misidentification of a quote from Glenn Fennelly was corrected.