ERS: Flu Vaccine Possibly no Better than Placebo in Preventing
Exacerbations in Asthmatic Children
By Cameron Johnston
Special to DG News
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STOCKHOLM, SWEDEN -- September 16, 2002 -- Asthmatic children and other
groups are usually encouraged to receive the flu vaccine each year as
winter
approaches. However, according to one study, the flu vaccine may be no
better
than placebo for preventing influenza-induced asthma exacerbations among
children.
The study by practitioners at Erasmus University Medical Center, in
Rotterdam, the Netherlands was presented in a poster session here on
September 15th at the 12th Annual Meeting of the European Respiratory
Society
(ERS).
They began with a large cohort of 3220 asthmatic children aged six to18
years, whose names were drawn from family practices in the western
Netherlands. They enrolled a total of 696 of the children. The study was
randomised, double blind, and placebo-controlled.
One group of 347 subjects received a parenterally administered, inactivated
influenza vaccine (flu shot), while 349 received a placebo throughout the
winters of 1999-2000, and 2000-2001. Primary outcomes were number, duration
and severity of asthma exacerbations associated with virologically proven
influenza infection.
The children or their parents were asked to use a physician-derived
checklist
to keep track of exacerbations and to report any symptom score of four
points
or more. Those who had symptom scores of four or more points would be
invited
to the clinic to take part in further tests, mainly involving a throat
swab.
Forty-four subjects in total underwent throat swabs. Those swabs that were
positive for influenza were implicated in 42 asthma exacerbations. The
exacerbations occurred in 24 of the patients who had received the vaccine
and
17 who had received the placebo. Although more exacerbations were seen in
subjects receiving the study drug, the difference was not statistically
significant (p=0.44).
After adjusting for confounding factors such as length of the season,
presence or absence of pets in the house, and presence of antibody titres
for
influenza, the researchers determined that the average exacerbation lasted
3.9 days longer in the placebo group, although there were no differences in
the severity of the exacerbations recorded between the two groups.
According to Dr. Herman Bueving, of the Erasmus Department of Family
Medicine, these findings suggest that while the flu shot does not reduce
the
number or severity of exacerbations in asthmatic patients, it can lead to
exacerbations of a shorter duration.
Nonetheless, this data also suggests that extra care should be taken each
year when winter approaches because not all asthmatics will have a
favourable
reaction to the flu shot, and some might even be better off avoiding this
form of prophylaxis altogether.