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 The findings help to explain why children often catch other
infectious diseases after having measles, and underscore the dangers
of growing resistance to childhood vaccination in some countries,
according to two studies published simultaneously.
They show for the first time how measles - one of the most
contagious diseases - resets the human immune system back to an
immature state like a baby's, with only limited ability to fight off
new infections.
The findings have implications for public health globally, since a
decline in trust in vaccines, and so in vaccination rates, is
leading to outbreaks of measles - which in turn can allow a
resurgence of other dangerous diseases such as flu, diphtheria and
tuberculosis.
"This ... is a direct demonstration in humans of 'immunological
amnesia', where the immune system forgets how to respond to
infections encountered before," said Velislava Petrova of Britain's
Wellcome Sanger Institute and Cambridge University, who co-led one
of the studies.
Stephen Elledge, a geneticist and researcher at the U.S. Howard
Hughes Medical Institute who co-led the second study, said its
results constituted "really strong evidence that the measles virus
is actually destroying the immune system".
The measles virus causes coughing, rashes and fever, and can lead to
potentially fatal complications including pneumonia and an
inflammation of the brain known as encephalitis.
Measles can be prevented with two doses of a vaccine that has proven
safe and effective and has been in use since the 1960s, but World
Health Organization (WHO) experts warned three weeks ago of an
"alarming upsurge" of cases in pockets of unvaccinated people in all
regions of the world.
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In the first three months of this year, the number of cases
quadrupled from the same period in 2018, WHO data show.
"The (measles) virus is much more deleterious than we realized,
which means the vaccine is that much more valuable," Elledge said.
For this research, the two teams looked at a group of unvaccinated
people in the Netherlands to find out what measles does to the
immune system.
In one study, they sequenced antibody genes from 26 children, before
and then 40 to 50 days after measles infection, and found that
specific antibodies that had been built up against other diseases
had disappeared from the children's blood.
Results from the second study found that measles infection destroyed
between 11% and 73% of the children's protective antibodies - the
blood proteins that "remember" past encounters with viruses and help
the body avoid repeat infections - leaving them vulnerable to
infections they had previously been immune to.
(By Kate Kelland, Health and Science Correspondent, Editing by Kevin
Liffey)
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