Published online August 1, 2005
PEDIATRICS
Vol. 116
No. 2
August 2005, pp.
562-563
(doi:10.1542/10.1542/peds.2005-0698GGG)
Influenza Vaccination in Children With Asthma: Randomized Double-Blind Placebo-Controlled Trial
Ariana D. Buchanan, MD and
Larry W. Williams, MD
Durham, NC
Bueving HJ, Bernsen RM, de Jongste JC, et al. Am J Respir Crit Care Med. 2004;169:488–493
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Purpose of the Study.
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To investigate if influenza vaccination in children with asthma
prevents asthma exacerbations provoked by influenza infection
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Study Population.
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Subjects were asthmatic children aged 6 to 18 years who had
no other chronic illness. There were 347 children assigned to
the vaccine group and 349 assigned to the placebo group.
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Methods.
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The primary outcome was the number of asthma exacerbations associated
with virologically proven influenza infection. Study subjects
and their families scored daily symptoms in a diary, and when
symptoms reached a predefined level, a pharyngeal swab for influenza
was taken. The symptom diary was maintained from the day after
administration of inactivated influenza vaccine or placebo on
approximately November 1 until April 1 of the following year.
Secondary outcomes included the duration and severity of the
asthma exacerbations, adverse effects of vaccination, and the
number, duration, and severity of all asthma exacerbations.
Influenza virus–specific antibody titers were measured
before vaccination, 14 to 21 days afterward, and at the end
of the influenza season.
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Results.
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In each group, 344 participants provided diary data for the
primary outcome. The groups were generally similar in baseline
characteristics, with almost 90% of children having used maintenance
medication for asthma in the previous 12 months. There were
486 reports of symptom scores that met the predefined criteria
for an asthma exacerbation (vaccine group: 251; placebo group:
235), with 42 of the resultant throat swabs testing positive
for influenza (vaccine group: 24; placebo group: 18). The difference
in the number of asthma exacerbations was not significant (95%
confidence interval: 34% reduction to 161% increase). There
were no significant differences found between the 2 groups for
any of the secondary outcomes measured. Antibody levels 14 to
21 days after vaccination were increased only in the vaccine
group. However, when comparing the 14- to 21-day titers to those
at the end of the season,
23% of subjects in the placebo group
and 10% in the vaccine group had a fourfold increase in influenza-specific
titers.
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Conclusions.
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The authors concluded that influenza vaccination was not more
effective than placebo in reducing the number of asthma exacerbations
caused by influenza infections in children.
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Reviewers’ Comments.
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Current guidelines that recommend the use of influenza vaccination
in asthmatics are based on epidemiologic evidence. A recent
Cochrane review on influenza vaccination in asthmatics found
insufficient evidence to make conclusions about the risks or
benefits of influenza vaccination, primarily because of a lack
of randomized trials. Although this study was a randomized trial,
the low attack rate of influenza (
6% of subjects tested positive
by pharyngeal swab) makes it difficult to draw conclusions from
the results. The study’s sample size was calculated based
on the assumption of a 30% influenza attack rate, leaving it
significantly underpowered to detect an effect at such a low
attack rate. If the question of efficacy of influenza vaccine
in reducing asthma morbidity is ever to be answered convincingly,
a large randomized trial, probably over several influenza seasons,
will be needed.
PEDIATRICS (ISSN 1098-4275). ©2005 by the American Academy of Pediatrics
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Purpose of the Study.
Study Population.
