a new study published in BMC Medicine by Santa Fe Institute
Omidyar Fellows Ben Althouse and Sam Scarpino. Their research points to a
different, but related, source of the outbreak -- vaccinated people who
are infectious but who do not display the symptoms of whooping cough,
suggesting that the number of people transmitting without symptoms may
be many times greater than those transmitting with symptoms.
In the 1950s, highly successful vaccines based on inactivated
pertussis cells (the bacteria that causes whooping cough) drove
infection rates in the U.S. below one case per 100,000 people. But
adverse side effects of those vaccines led to the development and
introduction in the 1990s of acellular pertussis vaccines, which use
just a handful of the bacteria's proteins and bypass most of the side
effects. (Currently given to children as part of the Tdap vaccine.)
The problem is, the newer vaccines might not block transmission. A January 2014 study in PNAS
by another research team demonstrated that giving baboons acellular
pertussis vaccines prevented them from developing symptoms of whooping
cough but failed to stop transmission.
Building on that result, Althouse and Scarpino used whopping cough
case counts from the CDC, genomic data on the pertussis bacteria, and a
detailed epidemiological model of whooping cough transmission to
conclude that acellular vaccines may well have contributed to -- even
exacerbated -- the recent pertussis outbreak by allowing infected
individuals without symptoms to unknowingly spread pertussis multiple
times in their lifetimes.
'There could be millions of people out there with just a minor cough
or no cough spreading this potentially fatal disease without knowing
it,' said Althouse. 'The public health community should act now to
better assess the true burden of pertussis infection.'
What's worse, their model shows that if the disease can be spread
through vaccinated, asymptomatic individuals essentially undetected, the
level of vaccination needed to protect those that are unvaccinated
(so-called 'herd immunity') is over 99 percent, impractically high at a
time when anti-vaccine campaigns are turning people away from
vaccination.
Their results also suggest that a practice called cocooning, where
mothers, fathers, and siblings are vaccinated to protect newborns, isn't
effective. 'It just doesn't work, because even if you get the acellular
vaccine you can still become infected and can still transmit. So that
baby is not protected,' Althouse says.
Does this mean the current vaccine is useless? Not at all, the pair
says. Until researchers can develop a new pertussis vaccine that blocks
transmission, the protection the acellular vaccine offers to individuals
is vital.
'It's the symptoms of pertussis infection that kill people,' Scarpino
says, 'and the existing vaccine prevents the most debilitating effects
of whooping cough.'
In that sense, the research underscores the importance of getting
vaccinated, especially for children. 'There are lots of people out there
who may be transmitting pertussis unknowingly,' Scarpino says. 'Not
vaccinating your own child puts her or him at increased risk of severe
disease, even death.'
https://www.youtube.com/watch?v=8qR8evyK5RA
https://www.pnas.org/content/111/2/787
https://shore-215.blogspot.com/2018/12/distinguished-ucla-professor-admits.html
https://www.scientificamerican.com/article/baboon-study-reveals
No comments:
Post a Comment