In 1964, the U.S. Public Health Service made a short film about measles, which was infecting up to four million Americans a year and killing 400 to 500 of them. A vaccine had just been licensed, and officials were hopeful the disease could be eradicated. In 2000, the Centers for Disease Control and Prevention declared measles eliminated in the United States. By 2016, it was eliminated throughout the Americas.
Then people started to forget. In October 2025, the Americas lost measles elimination status after Canada lost its own. The U.S. is holding on, but barely: cases are approaching 5,000 this year, the worst total since 1991.
There is some irony in all the forgetting, because forgetting is a hallmark of measles itself. It can cause immune amnesia, according to Dr. Andrew Pavia, chief of pediatric infectious diseases at the University of Utah. While measles produces terrific immunity to measles, Pavia says, it also destroys a good chunk of your immune memory. You lose the ability to fight pathogens your body has already learned to defend against because the immune cells that carry that memory are destroyed.
That leaves a person vulnerable to illnesses they were once protected against, through vaccines or past infection. The effect lasts at least a year, and some researchers think up to three. Pavia says that means that recovering from a measles infection may not be the end of the story, for some people.
“Measles is, I hate to say it, a gift that will keep on giving,” Pavia says.
What can you do?
- Check your vaccine status. Adults who aren’t sure they’re protected should catch up.
- Plan ahead if you might become pregnant. The vaccine isn’t safe during pregnancy, so check your immunity and get two doses beforehand if needed.
- Stay alert after measles. Researchers don’t yet know how best to protect people whose immune memory has been wiped out. Boosters of earlier vaccines are one idea, but it needs study. Meanwhile, pneumonia months after measles could turn severe quickly.
- Support public health. Outbreaks are labor-intensive to stop, and health departments need the funding and staff that have been cut.
