Whooping cough bacteria are becoming smarter
at colonizing and feeding off unwitting hosts, strengthening calls for a new
vaccine, according to UNSW researchers.
Australia needs a new whooping cough vaccine
to ensure our most vulnerable are protected from the emergence of superbug
strains, new UNSW research has shown.
The current vaccine, widely used since 2000,
targets three antigens in the bacteria of the highly contagious respiratory
disease which can be fatal
to infants.
All babies under six months old—in
particular, newborns not protected by maternal immunization—are
at risk of catching the vaccine-preventable disease because they are either too
young to be vaccinated or have not yet completed the three-dose primary vaccine
course.
Australia's whooping cough epidemic from 2008
to 2012 saw more than 140,000 cases—with a peak of almost 40,000 in 2011—and
revealed the rise of evolving strains able to evade vaccine-generated immunity.
In a series of UNSW studies, with the latest published
today in Vaccine, UNSW researchers took this knowledge further and showed, in a
world-first discovery, that the evolving strains made additional changes to
better survive in their host, regardless of that person's vaccination status.
They also identified new antigens as potential vaccine targets.
First author and microbiologist Dr. Laurence
Luu, who led the team of researchers with Professor Ruiting Lan, said whooping
cough's ability to adapt to vaccines and survival in humans might be the answer
to its surprise resurgence despite Australia's high vaccination rates.
"We found the whooping cough strains
were evolving to improve their survival, regardless of whether a person was
vaccinated or not, by producing more nutrient-binding and transport proteins,
and fewer immunogenic proteins which are not targeted by the vaccine," Dr.
Luu said.
"This allows whooping cough bacteria to
more efficiently scavenge nutrients from the host during infection, as well as
to evade the body's natural
immune system because the bacteria are making fewer proteins that our body
recognizes.
"Put simply, the bacteria that cause
whooping cough are becoming better at hiding and better at feeding—they're
morphing into a superbug."
Dr. Luu said it was therefore possible for a
vaccinated person to contract whooping cough bacteria without symptoms
materializing.
"So, the bacteria might still colonize
you and survive without causing the disease—you probably wouldn't know you've
been infected with the whooping cough bacteria because you don't get the
symptoms," he said.
"Another issue with the vaccine is that
immunity wanes quickly—so, we do need a new vaccine that can better protect
against the evolving strains, stop the transmission of the disease and provide
longer lasting immunity."
Vaccination still key but new vaccine needed
Prof Lan said while he would like to see a
new vaccine developed and introduced in the next five to 10 years, the research
team's important discovery did not render Australia's whooping cough vaccine
redundant.
"It is critical that people are
vaccinated to prevent the spread of whooping cough—the current vaccine is still
effective for protecting against the disease—but new vaccines need to be
developed in the long-term," Prof Lan said.
"We need more research to better
understand the biology of the whooping cough bacteria, how they cause disease
and what proteins are essential for the bacteria to cause infection, so that we
can target these proteins in a new and improved vaccine.
"This will all help to future-proof new
vaccines against the evolving whooping cough strains."
Dr. Luu agreed it was crucial that Australia
maintained its high vaccination coverage for whooping cough.
"Although the number of whooping cough
cases has increased during the past decade, it's still nowhere near as high as
what it was before the introduction of whooping cough vaccines," Dr. Luu
said.
"Therefore, we emphasize that Australia
must maintain its high vaccination coverage to protect vulnerable newborns who
are not protected by maternal immunity and cannot complete the three-dose
primary vaccine course until they are six months old.
"So, vaccination is especially important
for children, people who are in contact with children and pregnant women who
need the vaccine to produce antibodies to protect their newborns from
developing whooping cough in the first few weeks of life."
In addition to babies under six months having
a high risk of catching the disease, the elderly, people living with someone
who has whooping cough and people who have not had a booster in the past 10
years, are also most at risk.
Whooping cough is characterized by a
"whooping" sound and sufferers find it difficult to breathe.
The disease is more common during spring and
spreads when an infected person coughs or sneezes and other people breathe in
the bacteria.
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