2 weeks Ago By Sahan Weerasooriya
Just visualise the scenario where you spend years of your life building up a defence team in your body that remembers every invading enemy it has fought, from chickenpox to the flu, from pneumonia to skin infections and many, many, more. The body then goes on to build up a robust armamentarium to fight them the next time they attempt to cause trouble. This is what usually happens with our natural defence systems of the human body.
The memory of the attackers is the thing that leads to war being declared on them subsequently. Now, imagine a setting where disaster strikes in the form of some intruder who breaks in and erases those memories, leaving your body exposed and unprotected. We now know for sure that this is not a scene from a science fiction movie.
It is a real thing that takes place in the human body, called Immune Amnesia; the word amnesia being a glorified term for forgetting something. It is a situation where the body “disremembers” how to fight off diseases it once defeated. This kind of immune memory loss leaves the body wide open to catching infections that one was previously protected against.
It is not merely about getting sick again. It is about becoming vulnerable to a whole list of diseases, some of them serious, or even deadly. The human immune system is like an army that defends the body against harmful invaders like bacteria and viruses.
It has two main parts. One is the Innate Immune System, the first line of defence, a quick response team that is inherent in humans, which attacks anything unfamiliar. Humans are born with the capacity to direct this Innate Immune System to respond unreservedly to any harmful agent that invades the body.
The second line of resistance of the human defensive army is the Adaptive Immune System, which is the smarter component that specifically remembers past infections and builds explicit and precise weapons to fight them off more efficiently when the perpetrators try to attack the body a second time. These weapons include antibodies and immune memory cells. Thanks to this adaptive immune system, if you had chickenpox as a child, your body remembers how to fight it.
That is why one does not usually get it again. The flip side of the coin is that vaccines also work by training this adaptive memory system without one having to go through the actual disease. They are like military drills: safe practice sessions that teach the immune system to recognise and destroy certain pathogens before they get in and cause disease.
Think of your immune system as a vast library filled with records of every infection you have ever encountered. Each record contains information about the specific pathogen and instructions on how to fight it off. When you get a disease or receive a vaccine, new records are added to this library, ensuring that your body is prepared for future encounters.
This phenomenon of Immune Amnesia can occur after certain infections, most famously after contracting the measles virus. In recent years, scientists have come to understand this strange and troubling side effect of an illness that many once believed was simply “a childhood rite of passage.” Measles is not just a fever followed by a rash.
It is one of the most contagious diseases known to man, and it can have long-lasting effects on the immune system, even after recovery. Studies in the last decade have shown that measles can erase 20% to 70% of the immune system’s memory. In other words, if you’ve had 100 disease-fighting memory cells, measles might destroy even up to 70 of them.
As to how measles does it? Scientists believe that the virus attacks Immune Memory B cells and Memory T cells; these being the two types of specialised immune cells in the body that remember how to fight past infections. Once these cells are damaged or destroyed, your body has to start over from scratch, relearning how to fight infections it already knew how to handle before the “wiping out” of the process. The really creepy part is that Immune Amnesia does not make you feel sick right away.
You may feel perfectly fine after recovering from measles or a similar infection. But your immune system is now more vulnerable. A child who gets measles might recover from the rash and fever.
But in the months or years that follow, they could get pneumonia, ear infections, or diarrhoea far more easily than before. These secondary infections can be dangerous, even fatal. In fact, before widespread vaccination, measles did not just kill children through the measles virus itself.
Many died from other infections they caught in the months after measles had wiped out their immune memory. That is the reason why countries that introduced the measles vaccine not only saw a drop in measles cases, but also a drop in deaths from other diseases. It turns out that protecting against measles was protecting against a whole range of infections by safeguarding the memory of the immune system.
While measles is the best-known cause of immune amnesia, some scientists are exploring whether other infections might cause similar problems. There’s growing curiosity about whether certain viruses, like the flu viruses or even COVID-19, might temporarily reduce immune memory or even cause immune “confusion”, the latter term referring to a confused immune system attacking normal human tissues or exhibiting less effective responses against disease-causing organisms. While the research is still in early stages, one thing is clear: our immune systems are delicate.
Some infections do not just challenge the body, they even rearrange the entire system. This is where the conversation comes full circle. Vaccination is not just about avoiding a rash or a few days of fever.
It is about protecting the long-term memory of your immune system. If you prevent measles through vaccination, you do not just avoid one disease. You also prevent your immune system from being reset and losing its ability to fight off dozens of others.
This is why experts emphasise the importance of the measles, mumps, and rubella (MMR) vaccine. Despite its safety and effectiveness, some specific communities and groups of anti-vaxxers have become hesitant or sceptical about vaccines, often due to misinformation and disinformation. But studies have shown that in communities where vaccination rates drop, not only does measles come back, but so do many other infections.
It is just like pulling a thread and watching an entire sweater unravel and disintegrate. Immune amnesia also has consequences for entire populations, not just individuals. When a community is mostly vaccinated, herd immunity kicks in.
This means that even people who cannot get vaccinated, like little babies or those with weak immune systems, are protected because the disease has nowhere to spread. But when vaccination rates fall and diseases like measles spread, immune amnesia weakens the immune systems of those who get infected. This creates a ripple effect where many other infections spread more easily, even to people who never had measles.
In other words, immune amnesia can help fuel epidemics of other diseases. That is a very heavy price to pay for skipping a simple vaccine. Immune amnesia is not just a curious biological fact.
It is not just another strange scientific fact that might just blow away. It has very serious implications for public health. It could explain why some people get sick more often after recovering from certain infections, and it adds weight to the importance of vaccinations.
The good news is, immune amnesia can be prevented, and the solution is quite a bit straightforward. ONE CLEAR POSITIVE STEP IS TO GET VACCINATED AGAINST DISEASES, PARTICULARLY THOSE THAT ARE KNOWN TO INDUCE IMMUNE AMNESIA. This is particularly important against measles.
We need to educate the general public, and this article is a committed attempt to do just that. The society at large should intensely support the public health measures undertaken to facilitate satisfactory vaccination initiatives. If the general public has some concerns regarding vaccines and vaccination, they should promptly ask relevant questions from the proper authorities.
It would be most unwise to be guided by portals such as social media. The World Health Organisation (WHO) recently reported that measles cases in the European region more than doubled from 2023 to 2024, reaching about 127,000, the highest number since 1997. The increase has been linked to a lack of vaccination coverage.
It is estimated that half a million children across some parts of the world, which comprises 53 countries in Europe and Central Asia, missed their first dose of the measles vaccine in 2023. Children aged 5 years or younger accounted for about 2 out of 5 cases of the highly transmissible infectious virus. Immune amnesia is a powerful reminder of how interconnected our health profile really is.
One little bug can undo years of carefully crafted immune protection, making the body forget how to fight off old foes. Measles is the best-known example, but scientists are watching for other culprits. The takeaway message is very clear: diseases like measles are not harmless childhood illnesses.
They can cause long-term damage, even after the obvious symptoms are gone. Vaccines protect us not just from the disease, but from its deeper and widespread consequences, including Immune Amnesia. So, the next time you think of measles as just a spotty rash, remember that it also can wipe the slate clean, leaving your immune system defenceless and your body at woeful risk.
BY Dr B. J. C.
Perera MBBS(Cey), DCH(Cey), DCH(Eng), MD(Paed), MRCP(UK), FRCP(Edin), FRCP(Lond), FRCPCH(UK), FSLCPaed, FCCP, Hony. FRCPCH(UK), Hony. FCGP(SL) Specialist Consultant Paediatrician and Honorary Senior Fellow of the Postgraduate Institute of Medicine, University of Colombo, Sri Lanka.
Joint Editor, Sri Lanka Journal of Child HealthSection Editor, Ceylon Medical Journal.
