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Resistance
To Whooping Cough Vaccine Growing
(Reuters Health) - The
bacterium that causes whooping cough is mutating to develop resistance to the
vaccine used to immunise Dutch schoolchildren against the disease,
researchers report.
"It seems like the bacterium is changing part of its coat, thereby
disguising itself'' from the immune system, according to Dr Audrey King of
the National Institute of Public Health and the Environment in the
Netherlands.
She presented the findings to the American Society for Microbiology.
Until the advent of the pertussis (whooping cough) vaccine in the early
1950s, the respiratory illness was a major cause of illness and death,
especially among infants and small children. Since the introduction of the vaccine
(usually administered as part of the diptheria-tetanus-pertussis combo
vaccine), rates for whooping cough have dropped dramatically in the developed
world.
However, in recent years whooping cough has been making something of a
comeback in the Netherlands, the United States and elsewhere. Comparing old
and new strains of the Bordetella pertussis bacterium under the microscope,
King and her colleagues found that, over time, ``at least two proteins
located on the outside of the bacterium have been changed.''
Since vaccines work by "priming'' the human immune system to recognise
(and attack) such proteins, these changes could explain why the pertussis
vaccine now provides Dutch children with weaker protection against whooping
cough than it did in years past.
This theory was supported by further studies in mice. After administering the
vaccine to a group of mice, King's team infected them with either an older or
present-day version of the whooping cough bacterium. The result? More mice
infected with current strains of pertussis showed signs of illness than those
infected with strains dominant in years past.
King stresses that the whooping cough vaccine remains "effective against
serious disease,'' and there is no cause for immediate alarm. And she said it
is difficult to say whether vaccines used in other countries share
deficiencies similar to the form of the vaccine used in the Netherlands.
"However, there is still room for improvement,'' King adds, because
whooping cough vaccines currently in use may not protect children from less
serious forms of illness.
She recommends children receive booster shots of new and improved vaccines
-that recognise the bacteria's altered "coat''- in those countries where
they are available.
24/05/01
Further reading
Whooping Cough
(Pertussis) - Xtra Health guide
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