ERS: Flu Vaccine Possibly no Better than Placebo in Preventing Exacerbations in Asthmatic Children
By Cameron Johnston
Special to DG News
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.