Measles is far more dangerous than most people realize, new research shows.

The disease itself can cause a severe and sometimes deadly illness, but two new studies published on Thursday found that even when patients recover, the virus can inflict lasting harm on their immune systems.

The weakened immunity leaves a child vulnerable for several years to other dangerous infections like flu and pneumonia. The damage occurs because the virus kills cells that make antibodies, which are crucial to fighting off infections.

Scientists call the effect “immune amnesia.” During childhood, as colds, flu, stomach bugs and other illnesses come and go, the immune system forms something akin to a memory that it uses to attack those germs if they try to invade again. The measles virus erases that memory, leaving the patient prone to catching the diseases all over again.

The findings make the need for measles vaccination even more urgent, because it protects children against much more than measles, the researchers said.