UK Health Radio - Medical News Update on the Hour
An alarming report recently from the BBC that has
highlighted the fact that whooping cough may be evolving to outsmart the
currently used vaccine, say researchers.
Analysis
of strains from 2012 shows the parts of the pertussis bacterium that the
vaccine primes the immune system to recognise, are changing.
It
may have "serious consequences" in future outbreaks, UK researchers
state in the Journal of Infectious Diseases. But experts have stressed the
vaccine remains highly effective in protecting the most vulnerable young
babies.
There
has been a global resurgence of whooping cough in recent years. In 2012, there
were almost 10,000 confirmed cases in England and Wales - a dramatic increase
from the last "peak" of 900 cases in 2008.
The
outbreak led to 14 deaths in babies under three months of age - the group who
are most vulnerable to infection.
Rising
figures prompted health officials to recommend vaccination of pregnant women so
immunity could be passed to their newborns - a strategy that a recent study has
shown is working well.
But
there has been much debate among experts about whether the introduction of a
new vaccine in 2004 has been a factor in rising rates of whooping cough.
One
issue is that immunity from the newer acellular vaccine - which contains
specific proteins from the surface of the bacteria - does not seem to last as
long as the previous whole cell version, leaving teenagers and adults lacking
protection.
In
the latest study, researchers analysed the genes coding for the proteins on the
surface of the pertussis bacterium responsible for the UK outbreak.
They
found proteins being targeted by the vaccine were mutating at a faster rate
than other surface proteins not included in the vaccine.
Potentially
it means the bacteria is changing quickly to get around immune system's
defences put in place with immunisation.
Whooping
cough mostly affects infants, who are at highest risk of complications and even
death. The earliest signs are similar to a common cold, then develop into a
cough and can even result in pneumonia. Babies may turn blue while coughing due
to a lack of oxygen. The cough tends to come in short bursts followed by
desperate gasps for air (the whooping noise)
Adults
can be infected - but the infection often goes unrecognised
But
the researchers are still trying to work out what the changes mean in reality -
for example do the mutations boost the ability of the bacteria to cause
infection?
"We
wanted to look at strains from the UK to see if there was anything sudden that
had occurred that had led to these really large outbreaks," said study
leader Dr Andrew Preston from the University of Bath, said.
Vaccine effectiveness
The
"million dollar question" he said was what, if anything, could be done
to improve the vaccine - which is still the best defence we have - and prevent
future outbreaks.
Options
to consider include adding more or different proteins to the vaccine, adding
novel adjuvants - chemicals which boost the immune response, or even revisiting
the old-style whole cell vaccine, he said.
"Pertussis
has a cyclical nature and other big question is are we going to see another
increase in late 2015?" he added
Prof
Adam Finn, a paediatric immunology expert at the University of Bristol said the
importance - or not - of the subtle changes found in the study was as yet
unclear.
"But
the control of pertussis is a significant worry," he added.
Only
60% of pregnant women have had the pertussis vaccine and we should be doing
more to raise awareness of its benefits, he said.
"There
is very good new evidence that vaccinating pregnant women protects their
babies. And the group we really want to protect is new-born babies," he
said.
Amanda Thomas
UK Health Radio - Medical News Update
on the Hour
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