What is immune amnesia, and how does it relate to measles?
Your immune system is like your own private army, and like any army, there are distinct roles that different cells have. Memory cells, which are your B cells and T cells, are like your special forces — they’re well trained for specific tasks. In this case, when you are exposed to infections, whether it’s through a vaccine or natural exposure, these memory cells develop specialized abilities to attack and kill the infected cells when they enter your system. That’s the premise of vaccines — that you have these cells that wait until you need them, and you have other immune cells that circulate in your body all the time. When you’re exposed to an infection, the special forces cells are called in to win the battle.
With measles, researchers have done studies on immunity in macaques, a type of monkey, and they found that if you infect a macaque with measles, then these special forces — the memory B cells and T cells — get infected by the virus and are eliminated. A few studies have looked at this in humans with measles and found this happens to them as well.
Immune amnesia means that all the things you had developed protection against no longer exist. Your body doesn’t remember that it knew how to kill these different infections because all these memory cells were wiped out. You basically have to start over and retrain your special forces, which takes a long time. You will have immunity against measles, but you can no longer protect yourself against the other infections that you may have encountered over the years.
How can measles cause immune amnesia?
All viruses have the ability to modulate your immune system. There are cell receptors on the surface of our cells, which are like landing ports, that allow a virus to invade. In the case of measles, your memory B and T cells have a landing port that measles, specifically, can attach to and infect. Your body will have to kill these infected memory cells to get rid of the disease, making them collateral damage.
Other viruses don’t necessarily attack your memory B and T cells, but measles attacks them specifically. Interestingly, this does not happen with vaccines. When you get the measles vaccine, you will develop a protection against measles and will keep your protection against other infections that you’ve been exposed to or have been vaccinated against. This shows that there is a downside to having “natural immunity” for measles instead of being protected via vaccination, because you’re at risk of immune amnesia.
How common is immune amnesia among people sick with measles, and does its commonality differ between adults and children?
Virtually everyone who gets measles experiences some level of immune amnesia, but the extent can vary. However, children with severe measles seem to be impacted more than adults.
Is immune amnesia more serious for adults or for children?
It’s hard to say as there are many variables that also may be in play — including underlying disease states like malnutrition — that can impact a person’s immunity. These conditions, compounded with immune amnesia, may make someone more susceptible to other infections.
What are the main dangers or health risks of immune amnesia?
It makes you more susceptible to other types of infections. Even if you have survived measles and didn’t end up hospitalized or developing serious complications, you’re now defenseless in terms of other common infections that you might encounter. This is especially true for children, who can face much more severe and complicated infections.
By not having that extra immunity, you may be more at risk of a secondary infection. You could be more susceptible to chickenpox or the bacteria that causes pneumonia or meningitis. All these extra protections against bacteria or other viruses are now gone.
If you have immune amnesia, are you at risk of potentially losing your immunity to any virus you have been exposed to throughout your life, or does it eliminate immunity from only certain diseases?
You potentially can lose antibody protection to any viruses or bacteria that you have encountered in your life, but the degree of this loss may vary significantly.
How long does immune amnesia last?
I’ve seen two different studies. One found that it can last two to three years, and another study found that it can last up to five years.
Think of when young children go to daycare and regularly become sick because they don’t have immunity to infections yet. But when they get older, they get sick less often because they’ve already been exposed, and their memory cells are now able to combat the infections. When you lose that with immune amnesia, you’re basically starting over. It’s like starting daycare over again.
Are there ways to treat immune amnesia?
No. It takes time and effort to retrain your memory cells. There is no way to hurry it up. It’s not something your body can suddenly do.
Are there ways to prevent immune amnesia from happening?
Don’t get measles — and the best way to not get measles is to get vaccinated. This allows your immune system to develop that protection from measles without facing the consequences of it, like immune amnesia. Natural immunity is not better than vaccination.
Immune amnesia appears to be a lesser-known potential harm of getting measles. What are other health risks associated with getting measles that people should be aware of?
People can develop pneumonia, which is why people often get hospitalized. You can get a secondary bacterial infection on top of that, which is problematic because your lungs are already distressed, and it can make you very sick. You can also experience brain swelling, which is called encephalitis, and that can be incredibly dangerous.
According to the U.S. Centers for Disease Control and Prevention, about one out of five people who get measles will be hospitalized, and one to three out of 1,000 people with measles will die.
What should people do to best protect themselves from measles?
There is nothing that has been shown to prevent measles besides vaccines, which are very safe and effective. I recommend checking your immunization records. If you were born between 1963 and 1989, it’s possible that you only got one vaccine dose instead of two, which is the standard today. If you’re unsure if you got two doses, you can get another vaccine — getting an extra vaccine poses no issues or consequences — or you can ask your provider to get a blood test and see if you’re already immune. If you have any concerns or questions, ask your provider.
Keep in mind that the safety of vaccines has been well established. These are not new vaccines. They were developed in the late 1950s and approved in 1963. There are potential side effects, just like with other vaccines or medications, but we’ve figured out how to mediate those risks. Vaccines are protective, they’re safe, and when you consider the side effects like potentially having a sore arm or a fever the next day, those are much less problematic than the long-term consequences of getting measles and potentially having immune amnesia or a secondary infection.
