Measles Resurgence: The Hidden Toll of Immune Amnesia and the Urgent Need for Vaccination
A quick post on measles induced immune amnesia and the Texas outbreak.
Once considered nearly eliminated in many developed countries, measles is back. And with it, a subtle but important threat to our immune system, immune amnesia. This is the phenomenon by which a measles infection wipes away the immune memory that has been built up over years. This leaves survivors susceptible to a range of other infectious diseases that they may have been less susceptible to had they not been infected with measles. The recent outbreak in Texas has given us a stark reminder of measles’ potential to spread in communities that have declining vaccine coverage. In this post we’ll look into the biology of measles, including the groundbreaking studies that exposed how the virus undermines the immune defense. We’ll end with a review of the vaccine’s safety profile and benefits.
Measles is more than just a rash
Before widespread vaccination, measles was basically an inevitable childhood infection. This was in part due to its ability to stay around in the environment for extended periods of time after an infected person leaves the room. Historical records show that in the pre-vaccine era nearly every child contracted the virus with about 2.6 million deaths around the globe every year. While its clinical manifestations (rash, fever, cough) are well known, the real danger of measles is found in its ability to disturb our immune systems.
Arguably, the most critical and underappreciated consequence of a measles infection is immune amnesia. In a groundbreaking 2015 study, Michael Mina and colleagues [1] showed that the measles virus infection diminishes the preexisting antibodies that fight against other pathogens. A follow up in 2020 showed that the immune suppression leads to long term gaps in immunological memory [2]. In a complementary finding, researchers found that the recovery of B-cell diversity post-infection is incomplete, leaving survivors with a lessened ability to fight off later infections [3].
The discovery of immune amnesia reshaped our understanding of measles. It was no longer a self contained illness. Measles acts as a reset button for the immune system as it actively reduces levels of the preexisting antibodies that we build up over a lifetime of vaccines and infections. This means that individuals lose as much as 40% of their acquired protection from other pathogens. The process involves the depletion of memory B cells, critical components that allow the immune system to quickly detect and respond to pathogens it recognizes. The follow up work by Mina’s group in 2020 on macaques demonstrated that the virus induces broad suppression that persists long after the clinical symptoms of infection have cleared [2]. The findings were confirmed by the WHO’s technical report on measles induced immune amnesia [11].
There are also the severe complications beyond immune amnesia that can be devastating. Yes, most cases resolve without major incident, but complications like pneumonia and encephalitis are major contributors to its global mortality burden statistics. Of particular note is subacute sclerosing panencephalitis. This rare but fatal progressive neurological disorder occurs in roughly 1 in 10,000 to 1 in 100,000 measles cases. The CDC clinical guidelines provide a detailed account of these complications, noting that higher income countries typically fall between 0.1 and 0.2%. This can surge in settings with less healthcare access [4].
Historical observations, like those by Panum in 1846 during the Faroe Islands epidemic give us early epidemiological insights into measles’ complex transmission dynamics [5]. The impact of measles on communities and the needed public health response were changed forever when the attenuated measles vaccine was introduced in the 1960s [6]. The breakthrough brought in a new era of measles control, with drastic reductions in both incidence and mortality while preventing the longterm immunological harm that comes with a natural infection in the form of immune amnesia. Vaccines were already averting the hidden threat.
Vaccine efficacy and measles control
The introduction of the measles vaccine has arguably been one of the most remarkable success stories in public health history. The effectiveness of the vaccine has been confirmed over decades, with the data showing dramatic declines in measles incidence following immunization practices.
Vaccine Safety and adverse event rates
Concerns about the vaccine’s safety are understandable. Extensive research confirms that the measles vaccine is exceptionally safe. The The Institute of Medicine reviewed the literature and found no causal link between MMR vaccines and autism, identifying only rare and rather mild adverse events [7]. Fever was found to happen in about 5-15% of recpients, a transient rash in about 5%, and febrile seizures in about 1 in 3000 doses. The Cochrane Review, in an analysis of 138 studies and over 23 million children also found no link between the MMR vaccine and autism, asthma, or leukemia. It also determined that serious adverse events are extremely rare, happening in less than 1 per 100,000 doses. Global safety data from the WHO reported anaphylaxis rates of 1-3 cases per million doses and thrombocytopenia in about 1 per 30,000 doses, with the adverse events typically resolving without need for treatment [9]. The CDC’s report on the subject documents more than 20 years of the measles elimination effort in the Americas. During this time more than 500 million doses were administered without any vaccine derived cases of measles or fatal adverse events. Contrary to the common myths, the measles vaccine’s benefits severely outweigh the minimal risks. Especially when considering the vaccine’s safety profile to the dangers of natural infection.
The Texas outbreak has become a natural experiment in vaccine hesitancy
In communities where vaccine hesitancy has taken root, the re-emergence of measles has become a present day crisis in the making. Local health departments in Texas have reported clusters of measles cases in areas with particularly low immunization rates, a pattern that aligns with predictions made by outbreak tracing systems [12, 13]. We’re approaching 300 cases across 15 states on 3/20/2025 as I write this.
The Texas outbreak has unfolded quickly, spreading across states and impacting both school age children and young adults. The situation is made much more difficult because of the challenges associated with communicating the long term impacts measles comes with. Many members of the public see it as a benign illness of childhood, and who can blame them when most people before the 60s caught it and lived. But the newly discovered phenomenon of immune amnesia, which can wipe away decades of acquired immunity, shows us the importance of vaccination regardless of how mild the visible symptoms seem.
The outbreak in Texas also has similarities to challenges seen in other regions, like Brazil and Venezuela, as reported by the Pan American Health Organization [14]. The convergence of vaccine hesitancy and gaps in healthcare access create a perfect scenario for measles to re-emerge.
A bridge between science and policy
Public health policy has the challenge of translating research into actionable strategies. This is no easy process. The extensive body of evidence demonstrates that measles is not just a benign childhood illness. It triggers a long lasting decline in immune memory which has been described by Dr. Michael Mina as a “hidden cost” of infection, due to the physical symptoms being most well known. Moving forward, policy makers, healthcare providers, and science communicating community leaders need to translate these new insights into action. Keeping vaccination coverage high prevents not only measles, but helps to preserve our precious immune systems. Let the lessons of immune amnesia and the Texas outbreak remind us that coordinated community health initiatives and clear science communication are key to protecting public health.
References.
Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens" (https://doi.org/10.1126/science.aay6485)
Measles virus immune suppression: Lessons from the macaque model" (https://doi.org/10.1371/journal.ppat.1008095)
Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles” (https://doi.org/10.1126/sciimmunol.aay6125)
"Measles (Rubeola): For Healthcare Providers" (https://www.cdc.gov/measles/hcp/index.html)
"Observations Made During the Epidemic of Measles on the Faroe Islands"(https://jamanetwork.com/journals/jama/fullarticle/333027)
"Studies on an Attenuated Measles Virus Vaccine"(https://doi.org/10.1056/NEJM196205242662103)
"Adverse Effects of Vaccines: Evidence and Causality"(https://doi.org/10.17226/13164)
MMR Vaccine Safety and Efficacy" (https://doi.org/10.1002/14651858.CD004407.pub4)
"Measles Vaccines: WHO Position Paper"(https://www.who.int/publications/i/item/weekly-epidemiological-record-92-17-205-228)
"Measles Elimination in the Americas (2000–2020)"(https://www.cdc.gov/mmwr/volumes/70/wr/mm7023a1.htm)
"Measles and Immune Amnesia: Current Evidence"*](https://www.who.int/immunization/sage/meetings/2019/april/2_Previous_meetings_Immune_amnesia_final.pdf)
"Measles Outbreak Archive" (https://promedmail.org/)
"Measles in Europe" (https://www.ecdc.europa.eu/en/measles/surveillance/atlas)
"Measles in Venezuela and Brazil (2018)"*](https://iris.paho.org/handle/10665.2/55126)