Longterm damage from measles
Sufferers who escape without developing pneumonia, brain
swelling, or other serious complications may believe the worst is over.
Yet the measles virus has only gotten started.
The virus also damages the immune system,
leaving people vulnerable to other infections for up to five years.
“The rash and the fever, that’s the tip of the iceberg,”
Michael J. Mina, MD, PhD, coauthor of two seminal studies in Science on the effect of measles on the immune
system, told CIDRAP News. “The majority of the damage being done is under the
surface.”
The measles virus hijacks the immune system, using
specialized memory cells to make copies of itself before blowing them up, Mina
said. By deleting the body’s memory of earlier infections, measles causes a
condition called “immune amnesia.”
Without those memory cells, the body essentially forgets how
to fight off infections it defeated before. That leaves people newly vulnerable
to bacteria and viruses against which they were once protected, either through
infection or vaccination.
‘Thousands of additional medical clinic visits’
Immune amnesia “happens in 100% of measles-infected
individuals to some degree,” Mina said.
The condition causes more harm in some people than others,
depending on how much immune memory is deleted, which immune cells are
destroyed, and a person’s age and underlying health, Mina said.
A child whose immune system forgets how to fight off the
common cold, for example, may suffer the sniffles and sneezes of last year’s
respiratory viruses a second time.
But a baby who loses the protection provided by whooping
cough (pertussis) vaccines could end up hospitalized.
A woman who loses her immunity against chickenpox, which
causes much more severe disease in adults than in children, could develop
pneumonia, Mina said.
With more than 6,000 measles infections
in less than two years, immune amnesia could pose a real threat, Mina said.
“We will see thousands of additional medical clinic visits,”
said Mina, chief medical officer at Invivyd, a biotech company developing
experimental treatments for measles. “If your child gets measles, you have to
be looking over your shoulder” for years.
Children in poor health are especially vulnerable
Children who are sick or malnourished before contracting
measles are especially vulnerable to additional infectious diseases, said
Boghuma Titanji, MD, PhD, an infectious disease specialist and assistant
professor of medicine at the Emory University School of Medicine.
Titanji treated many children affected by immune amnesia in
Cameroon, which has one of the highest rates
of measles in the world. Those suffering from malnutrition were more likely to
be hospitalized, she said.
“After a child is admitted to the hospital for measles,
they're more likely in the year or two that follows to be readmitted multiple
times for a variety of viral, bacterial, or parasitic infections,” Titanji
said.
In West Africa, children who survived measles were more likely to be later infected with malaria, Titanji noted. “In general, they were just more sickly children,” she said.
But immune amnesia isn’t limited to developing nations.
Recent studies have found evidence of immune amnesia in
wealthy countries with strong healthcare systems, including Germany, Israel, Switzerland and the United Kingdom. Children in these
studies who had been infected with measles were more likely than others to need
antibiotics or visit the doctor.
“Immune amnesia is probably something that we're going to
encounter” in the United States, said C. Mary Healy, MD, an associate professor
of pediatrics and infectious disease specialist at Texas Children’s Hospital.
“We’re on the cusp of finding out just how significant immune problems may be.”
Pain seared into her memory
When Crystal Webster moved to Switzerland in 2008 at age 27,
she wasn’t aware that the country was experiencing its largest measles
outbreak in years.
Like most children born in the 1980s, Webster received a
single dose of measles-containing vaccine as a baby, which was standard
practice at the time. One dose of the measles, mumps, and rubella vaccine prevents 93% of
measles infections; two doses prevent 97%.
When Webster broke out all over in red pustules that looked
“almost like zits,” she looked up her symptoms online. She learned that her
itchy rash, fatigue, cough, runny nose, and pink eye were all classic symptoms
of measles.
The misery of measles is seared into Webster’s memory. She
felt a blaze of pain any time that one of the pustules came in contact with
something else.
“I remember lying on the wood floor, completely naked,
spread eagled, because I didn’t want any part of my body to touch any other
part of my body,” said Webster, now 44.
The summer heat made Webster’s skin feel even worse,
especially since her home had no air conditioning.
The following winter, Webster said, “I felt like I always
had a runny nose.” But she chalked her constant colds up to living in a new
environment with unfamiliar germs.
While it’s impossible for doctors to know for certain if
Webster’s symptoms were caused by immune amnesia, “her increased respiratory
infections in the year immediately following measles are certainly consistent
with what we know about this phenomenon,” Titanji said.
An unwelcome souvenir from her measles infection
A few years later, after Webster had returned to the United
States, she broke out in a red, painful rash around her waistline. A doctor at
an urgent care clinic confirmed Webster had shingles, which can afflict adults
who, like Webster, had chickenpox as a child.
Although chickenpox typically goes away after four to seven days,
the virus that causes the disease, called varicella-zoster, sticks around for
decades, hiding in nerve cells
of the spinal cord. The virus can re-emerge as people age or if they become
immune suppressed.
Shingles was just as painful as measles, Webster said. “I
wrapped my stomach in gauze so that my pants wouldn’t rub up against the
blisters,” said Webster.
Webster’s shingles infection also could have been caused by
immune amnesia, Mina said.
“It’s very likely her measles infection would have deleted
or drained a portion of her antibodies against varicella, driving her to have
increased susceptibility to [shingles] rearing its head early,” Mina said.
Webster said she assumed her infections were due to bad
luck.
“I was pretty young to have all these things,” Webster said.
“I thought I had done what I needed to do to be healthy.”
Difficult diagnoses to make
Like Webster, many people with immune amnesia don’t connect
their illnesses back to measles, said Pia Pannaraj, MD, MPH, vice chair of the
American Academy of Pediatrics’ (AAP) Committee on Infectious Diseases.
Measles amnesia “often goes undiagnosed,” said Pannaraj, who
has treated measles patients in the United States, Asia, and Africa. “People
get measles, and then afterwards they will have recurrent ear infections or
pneumonia, but they don’t tie it back to measles. They think, ‘Oh, this is just
bad luck that I happen to have this ear infection or that I got pneumonia.’”
Even doctors may be unfamiliar with immune amnesia, which
scientists have only truly begun to understand in the past 15 years, Pannaraj
said. Most doctors learned little about the condition during medical school or
residency.
Pannaraj is a member of the Measles Collaborative, a newly
formed coalition of healthcare providers and public health experts that aims to
strengthen measles prevention, response,
and education.
“The people who are getting measles now tend to be those
that are unvaccinated and may not interact with the medical system very often,”
she said.
A childhood of illness
Before vaccines became available, virtually all children
contracted measles.
Suzanne, 71, became severely ill with measles when she was 6
years old, two years before the measles vaccine was released.
“It’s been over 60 years, and I can still picture how sick I
was,” said Suzanne, a human resources consultant who lives in Fort Myers,
Florida, and asked to be identified only by her first name to protect her
privacy. Suzanne’s account of her illness was confirmed by her older sister.
Suzanne said she remembers lying in bed, with “big sheet around me like a tent” to
protect her eyes, which measles had made very sensitive to light.
“My mother put cold, damp clothes on my head, and everyone
was standing around like, ‘Is she going to die?’” Suzanne recalled. “My parents
said I was on the verge of being hospitalized when my fever broke.”
Although Suzanne remembers being healthy before contracting
measles, she said the virus left her very weak. She was too sick to return to
school for weeks.
“I was very sickly as a child after that,” Suzanne said. “I
seemed to get everything. I got every cold that went around. I was prone to
like urinary infections, kidney infections, respiratory infections.”
Six years after her measles infection, Suzanne and her two
siblings contracted chickenpox. Suzanne suffered the most, and still has scars
on her face from the blisters.
Suzanne said she learned about immune amnesia from her
sister, a nursing professor. She wonders if her sickly childhood—and continuing
immune problems as an adult—were caused by immune amnesia.
‘A shadow of death’
Doctors have known for hundreds of years
that measles can lead to later waves of disease.
After a measles outbreak, “there would be a shadow of death
that would linger for months,” Mina said. “Measles outbreaks were
extraordinarily predictive of the amount of death that would happen from all
other infectious diseases in a community.”
Yet doctors also reported sporadic cases in which measles
survivors benefitted from a less aggressive immune system, Mina said.
In the pre-vaccine days, doctors wrote letters to the
editors of medical journals about children with autoimmune disorders—which
result from a hyperactive immune system—whose disease went away after a measles
infection, Mina said.
Scientists have only recently begun to understand how
measles causes immune amnesia.
In 2012, animal studies showed the measles virus destroys immune cells called memory
T cells and memory B cells, which help the body recognize other infections.
Without memory cells to make antibodies, the immune system has no targeted
defense against diseases the body has seen before. The authors of the study, published in PLOS Pathogens,
coined the term immune amnesia.
We’re on the cusp of finding out just how significant
immune problems may be.
Even then, scientists believed that measles suppressed the
immune system only for weeks or months.
In 2015, Mina was part of a team of researchers who
discovered that children take two to three years to recover
antibodies lost to measles. Authors of a 2018 study based on a British medical
database found increased rates of infections
in measles survivors for up to five years.
In 2019, Mina and his colleagues showed that measles
survivors lose 11% to 73% of
the antibodies they had before getting sick. It’s not possible to predict who
will suffer the greatest harm.
Rebuilding the immune system
The good news is that people rebuild their immune systems
over time, as they are exposed to viruses and bacteria, Mina said. Those
exposures can act like a booster shot to children who keep some immunity to a
disease.
In Mina’s study, for example, blood tests revealed that some
children were accumulating antibodies against respiratory syncytial virus
(RSV). That virus, which circulates in fall and winter, can cause severe
disease in newborns but symptoms similar to the common cold in older children
and adults.
“It turns out that what we were witnessing in real time was
people rebuilding their immune repertoire,” Mina said. The children with
increasing RSV antibodies were all in the same classroom at school. “We saw a
silent RSV virus going through the class.”
No universal recommendations
Doctors still have many questions about immune amnesia, such
as whether children should be revaccinated after having measles, said Healy,
also a member of the Measles Collaborative.
Doctors can’t easily predict “which parts of the immune
system have been wiped out by the measles infection,” Titanji said
Doctors may weigh the benefits of booster shots for children
who develop multiple infections after a case of measles, Titanji said. “It’s
really on a case-by-case basis; a provider would have to make that call.”
There’s no universal recommendation about revaccinating
people after a measles infection, Pannaraj said.
“It’s a question we’ve been thinking about, but there’s not
yet enough data” to issue recommendations, Pannaraj said. “To be honest, we
haven’t had to think about it much until now.”
One shot that protects against multiple diseases
Understanding immune amnesia helps explain why measles epidemics are so deadly—both during an outbreak and years later—and why maintaining high levels of protection against measles saves so many lives, Mina said.
Before measles vaccines were available, measles immune
amnesia caused about half of all
child deaths from infectious diseases.
In recent decades, campaigns to protect children through
measles vaccination have reduced overall child
mortality by 30% to 50% in countries with limited resources, and up to
90% in the poorest nations.
Comprehensive vaccination could prevent the 95,000 annual
deaths from measles, as well as hundreds of thousands of additional deaths
caused by lasting damage to the immune system, Mina said.
“This is why,” he said, “it’s so important to protect
against measles.”
