New Study Shows
How Measles Virus Infection Has Both Immediate And Lasting Impact As A
Cause Of Death
Mortality Burden is Astonishing
It is recognized from
epidemiologic studies that the risk of death from measles is increased
even after the acute phase of the illness. This has been perhaps most
notable in African children. The mechanism for this effect has not
been well understood. Now an international team of more than a dozen
researchers led by Michael Mina from Harvard’s School of Public
Health has provided evidence that measles virus (MV) infection
actually infects immune cells and causes immune suppression against a
much wider variety of pathogens than simply the measles virus itself.
Methods
Using an assay that
tracks the diversity of antibodies, the researchers examined blood
samples from children in the Netherlands before and after infection
with MV during a 2013 outbreak. They showed that infection caused an
11-73% loss in the pre-existing antibodies acquired by individuals
from past encounters with pathogens. Thus, the they show that the
impact of measles infection is both immediate and persists for an
extended period to make survivors more vulnerable to death from other
infectious diseases.
Astonishing Impact
In their paper
published in Science in November, the authors make the astonishing
suggestion that in the pre-vaccine era measles virus “may have been
associated with up to 50% of all childhood deaths from infectious
diseases, mostly from non-MV infections.” This is because it could
take measles survivors months or years to recover the kind and quality
of immune protection they had before MV infection.
Vaccine Safe &
Valuable
The good news from the
report is that infection with attenuated measles vaccine virus through
vaccination does not appear to produce the same immunosuppressive
effects. This means that an already valuable measles vaccine has now
been shown to be even more valuable because it can protect from a much
wider variety of infectious causes of death. In fact, the authors
offer the hypothesis that by preventing measles and what they call
“immune amnesia” the introduction of measles vaccine in the mid 1960’s
could have reset overall baseline morbidity and mortality rates to
lower levels.
Measles Control
According to the World
Health Organization (WHO), measles epidemics occurred every 2-3 years
in the prevaccine era and caused an estimated 2.6 million deaths each
year. We know from the WHO that the increased use of measles vaccine
between 2000-2017 when a new measles elimination initiative was
launched has succeeded in raising vaccination coverage with at least
one dose to 85%. (Two doses are optimal).
Associated with this
vaccination initiative, global measles deaths have decreased by 80%
from an estimated 545,000 in 2000 to 110,000 in 2017. Altogether, this
program has prevented an estimated 21.1 million deaths, according to
WHO.
However, measles has
been resurging more recently with declines in measles vaccination
since 2017 and it still causes over 100,000 deaths globally each year.
For example, last month the Epidemiology Monitor reported than an
ongoing outbreak in the Democratic Republic of the Congo has claimed
4,000 children’s lives because of failure to achieve adequate
vaccination coverage. Also, WHO reports that several countries have
recently lost their measles free-status. The results of the Harvard
study could reenergize efforts to increase coverage even higher to
help prevent not only measles deaths but also hundreds of thousands
more caused by MV infection. ■
|