Measles, a highly contagious viral infection, is most recognized by its red rash and is caused by the morbillivirus. Transmitted through the air, measles is so contagious that for every 10 unvaccinated people exposed, nine will contract the virus. While the majority of measles cases are mild, the disease can lead to serious complications, some of which are only seen months or even years after the initial infection. One such long-term consequence is a phenomenon called “immune amnesia.”
Before the measles vaccine was introduced in 1963, the U.S. faced millions of cases annually, with thousands of hospitalizations, deaths, and long-term disabilities. However, vaccination efforts have dramatically reduced these figures by over 99 percent. “In a sense, we are victims of our own success,” explains Luis Ostrosky, an infectious disease physician at UTHealth Houston. As measles cases became rare, many people began to view the disease as a non-issue. But the recent resurgence of measles due to declining vaccination rates is bringing new attention to its potential long-term effects.
Measles and Its Risks
Measles is characterized by fever, cough, runny nose, watery eyes, and the signature red rash. People infected with the virus are contagious for several days before and after the rash appears. While most recover without serious issues, measles can lead to complications, including pneumonia, encephalitis (brain swelling), and, in rare cases, subacute sclerosing panencephalitis (SSPE), a fatal neurological disorder that can develop years after the infection.
A study by the CDC reveals that one in five unvaccinated individuals who contract measles will require hospitalization, and one in 20 children will develop pneumonia, the leading cause of measles-related death. Brain inflammation, known as encephalitis, can also affect one in 1,000 children, leading to long-term neurological issues.
The Role of Immune Amnesia
Immune amnesia refers to the phenomenon where the measles virus destroys the body’s immune memory. Normally, our immune system remembers past infections, enabling us to fight off recurrent pathogens. However, when someone contracts measles, the virus damages the immune system’s memory cells, which are crucial for recognizing and responding to future infections.
This makes individuals more vulnerable to other infections, such as the common cold or flu, as their immune systems lose the ability to quickly recognize and fight off these pathogens. The immune amnesia effect is especially pronounced in the months following measles infection, though it can persist for years. “The measles virus doesn’t just suppress the immune system; it rewires it,” explains virologist Rik de Swart from Erasmus University Rotterdam. As a result, the body’s defenses are left weakened, and individuals are more prone to additional infections.
Why Does Immune Amnesia Matter Now?
In the context of the ongoing global health challenges, immune amnesia poses an alarming risk. Studies have shown that a decline in measles vaccination rates could exacerbate future pandemics by leaving populations more susceptible to other diseases. For example, a 2021 study suggested that even small reductions in vaccination rates could make it harder to contain an outbreak, as a weakened immune system could amplify the effects of new infectious diseases.
Miguel Muñoz, a professor at the University of Granada, notes that the impact of immune amnesia could be dramatic: “You can believe you have herd immunity, but because of a lack of measles vaccination, you don’t.” This highlights the critical need for high vaccination rates, not just to prevent measles but to maintain the broader immunity of the population.
The Effectiveness of the Measles Vaccine
The measles vaccine, which is administered in two doses, offers long-lasting protection. The first dose is given between 12 and 15 months of age, and the second between ages four and six. One dose is about 93 percent effective at preventing infection, while two doses provide 97 percent protection, which lasts a lifetime.
“This vaccine is one of the most effective vaccines available,” says Ostrosky. “It rarely needs to be administered again.” For those unsure about their vaccination status, immunity can be confirmed through laboratory testing or by receiving another dose of the vaccine.
Conclusion
Immune amnesia underscores the importance of maintaining high vaccination rates, not only to prevent measles but also to protect individuals from a range of other diseases. The resurgence of measles, fueled by vaccine hesitancy and misinformation, brings the long-term effects of the disease back into focus. By understanding and addressing these risks, we can better safeguard public health and reduce the threat of future outbreaks.
