I remember learning back in medical school that both measles and tuberculosis were two very bad infections for children to get. Having both infections at the same time, I discovered while studying in the Philippines, leads to a disseminated, almost always fatal, form of tuberculosis: miliary TB. A new study, published in the journal Science, explains why it’s measles that hands down the death sentence.
It turns out that infection with the measles virus — still a major cause of childhood morbidity and mortality worldwide (145,000 deaths in 2013) — significantly damages the immune system for prolonged periods of time. Will Dunham cites the study’s importance in light of the recent outbreak of measles cases in the United States this past winter:
The research focused on a phenomenon called “immune amnesia” in which the measles infection destroys cells in the immune system, the body’s natural defense against disease-causing microbes, that “remember” how to fend off previously encountered pathogens.
Prior research had suggested “immune amnesia” lasted a month or two. The new study, based on decades of childhood health data from the United States, Denmark, England and Wales, showed the measles-induced immune damage persisted on average for 28 months.
During that period, children who got measles were more likely to die from other infections due to the long-lasting depletion of immune memory cells caused by the virus.
The end result is that vaccination with measles vaccine (MMR) prevents “measles-associated immune memory loss” — both at the individual level and the community (herd) level — that can lead to illness and death from other, common infectious diseases. Dunham spoke to the lead author:
“Our work reiterates the true importance of preserving high levels of measles vaccine coverage as the consequences of measles infections may be much more devastating than is readily observable,” Mina said.
The study showed preventing measles through vaccination lowered childhood deaths from pathogens that cause conditions like pneumonia, sepsis, bronchitis, bronchiolitis and diarrheal diseases.
The first MMR is given to children in the United States at 12-15 months of age, with a booster dose at 4-6 years. There is overwhelming evidence that the vaccine is safe and effective, and overwhelming consensus among pediatricians that the vaccine should be given without delay. Medical contraindications to this “live” vaccine are very rare; there are no other excuses for delaying or refusing an MMR vaccine for adults (if not already immunized) and children. And now we know why measles vaccine can protect children from getting sick and dying from other serious infections.
I hope that researchers look into “immune amnesia” with other viruses. I suspect we’ll find that getting sick with one virus lowers a person’s resistance to other infections, or sets them up for developing other medical conditions, such as autoimmune disorders, inflammatory conditions, and even cancer. For years we’ve been hearing about relationships between viruses and other, immune-mediated conditions: HPV and cervical and oral cancers; Epstein-Barr virus, HIV and Burkitt lymphoma; enteroviruses and type 1 diabetes.
Maybe now we know why.