Some parents believe a 'mild' case of measles is preferable to vaccination. A calculated risk that might seem reasonable on the surface. What many don't realize is that even mild measles cases trigger something called 'immune amnesia,' a process where the measles virus systematically destroys your body's hard-earned disease-fighting memory.
(A note on the post we are sharing above: we are doing our best to move away from the term "natural" immunity and instead use phrases like "survivor immunity," which more correctly capture the risks of infection.)
Surviving measles (again, even mild cases) wipes out a portion of your immune memory and weakens your body's defenses, leaving you vulnerable to infections you were previously protected against through years of exposure or immunization. Your body essentially loses years of immune education, forgetting how to recognize and fight off old enemies. This concept of 'immune amnesia' is a scientific discovery that many practicing doctors and clinicians may not be familiar with, as it only became well-established in the research literature within the last decade. Let’s discuss…
How Your Immune System Builds Its Defense Library
Think of your immune system as an army of immune soldiers trained against every germ you've ever encountered. Chicken pox at age 5? Your immune system was trained and filed the essential combat strategies away for use at a later date. That cold from last winter? Also saved for future reference. Years of exposure train your immune system to build a memory-based playbook of defense strategies. Pretty cool, eh?
Then measles comes along and ambushes your immune system army
This isn't just theory anymore; scientists can actually measure it. After a measles infection, your blood shows dramatically fewer immune memory cells. Destroying immune memory causes your body to forget how to recognize and defeat old enemies. Studies following unvaccinated children for years after measles infection found they became much more susceptible to infections they should have been able to fight off due to immune memory from previous exposure.
The measles virus erases your body's hard-won defenses
Research shows measles erases 11-73% of your body's disease-fighting knowledge, making you vulnerable to germs you could have beaten easily if your immune memory still existed. This explains why communities would get hit by waves of other diseases after measles outbreaks.
The most eye-opening aspect of this is that it happens even with mild measles cases. While your child is recovering from the rash and fever, their immune system is quietly being dismantled by the measles virus. The measles virus targets and destroys the very cells that contain your immunological memories. Your memory B cells and T cells that remember past infections.
The Discovery That Changed Everything
The breakthrough came through pioneering research led by Dr. Michael Mina (whom we were honored to have on our podcast, linked below!), first published in Science in 2015, which revealed that measles had long-term effects on immune function lasting 2-3 years. This was followed by groundbreaking 2019 research that Mina led using a tool called VirScan that could measure the exact extent of immune memory loss by tracking antibodies to thousands of different pathogens in a single drop of blood.
These studies demonstrated that measles doesn't just cause temporary immune suppression; it actually deletes your immune memory. As Mina described it: "Imagine that your immunity against pathogens is like carrying around a book of photographs of criminals, and someone punched a bunch of holes in it."
Here's where it gets interesting
The measles vaccine saves far more lives than measles deaths alone would account for. Why? Because vaccinated kids don't lose their memory-based immune defenses. They keep all those hard-won defenses against everything else.
But there's more to the story
Research suggests that people who had the measles, mumps, and rubella (MMR) or tetanus, diphtheria, and acellular pertussis (TDaP) vaccines may have memory T cells that, when reactivated, help fight novel pathogens never seen before, like SARS-CoV-2, the virus that causes COVID-19. This interesting nugget would explain why the measles vaccine is associated with reduced deaths even in places where measles hasn't been actively spreading.
The Long-Term Impact You Can't See
This immune memory loss caused by measles infection can last for years. Studies show the vulnerability persists for 2-3 years after infection, during which time children remain at heightened risk for secondary infections. The immune system can rebuild itself, but only through re-exposure to all those pathogens, essentially having to relearn everything from scratch.
The MMR vaccine also prevents other devastating complications like subacute sclerosing panencephalitis (SSPE), a rare but fatal brain disorder that develops years after measles infection. SSPE is nearly always fatal within 1 to 3 years, and vaccination against measles is the only known prevention. There is no possibility of contracting SSPE after vaccination; it has been proven that a direct measles infection must occur.
The bottom line
Measles doesn't just cause a rash that goes away. It steals years of immune protection, leaving you vulnerable to everything else your body once knew how to fight. This highlights why getting the measles vaccine is so important. It's not just about preventing measles; it's about protecting the germ-fighting immune memory defenses your body has earned over your entire lifetime.
Hear directly from one of the researchers who discovered immune amnesia on our podcast:
Get key takeaways from our resident immunologist, Dr. Aimee Bernard, in our "Fun Size Science" series (in this video, we discuss why MMR vaccines are recommended for babies once they turn 6 months old):
Join Jen and Jess for an informal chat about immune amnesia in our "Breaking Brews" series, where we break down health science over coffee.
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I'm a Pediatrician. I was born in 1956. I remember having measles when I was about 5. All my siblings had it and were all miserably sick. I was the sickest. I remember the doctor coming to our house. I was in bed, the curtains were drawn. I had a fever to 105 for over a week. I could hear my mom talking to the doctor, and I remember thinking "they think I'm going to die".
THAT's Measles. It's about as sick as people get. And everybody got it. Everybody.
No one in the 60's hesitated to get the measles vaccine when it became available, because they had all seen what the measles could do.
This information needs to be shared with vaccine skeptics. It could be a game-changer!