WASHINGTON — Measles has a stealth side effect: New research shows it erases much of the immune system’s memory of how to fight other germs, so children recover only to be left more vulnerable to bugs like flu or strep.

Scientists dubbed the startling findings “immune amnesia.” The body can rebuild those defenses — but it could take years.

And with measles on the rise, “it should be a scary phenomenon,” said Dr. Michael Mina of Harvard’s school of public health, lead author of research published last week in the journal Science.

“This goes under the radar” because doctors wouldn’t necessarily connect a child’s pneumonia to measles they suffered a year earlier, Mina explained. “But would they have gotten it if they hadn't gotten measles?”

The Harvard team analyzed blood samples taken from 77 children before and after a measles outbreak in an unvaccinated community in the Netherlands. They looked for antibodies, which remember viruses and bacteria they encounter to guard against a repeat infection. After recovering from measles, the youngsters were left with plenty of antibodies against that virus — but ones they had previously harbored against other germs had plummeted.

In the most severe cases, “they’re just as vulnerable as if they were infants,” said study senior author Stephen Elledge, a Harvard geneticist.

A separate study, published Thursday in Science Immunology, supported the findings. Researchers from Britain’s Wellcome Sanger Institute used the Dutch blood samples to genetically test antibody-producing cells, and concluded measles is eliminating enough to reset the immune system to a baby-like state.

If protection against the misery — and sometimes life-threatening effects — of measles isn’t enough reason to vaccinate children, specialists said the two studies offer a powerful new rationale.

“There really are profound gaps and holes” in someone’s immunity after measles, said Dr. Anthony Fauci of the U.S. National Institutes of Health, which helped fund the Harvard work. “You ultimately recover but after a year or two or sometimes more.”

“It’s doubly important to vaccinate children,” agreed Dr. Mark Mulligan of NYU Langone Health, who wasn't involved with the new research.

Lauran Neergaard is an Associated Press writer.