Dear Editor:
We commend the authors of the March 2009 Pediatrics article titled
“Allergic Disease and Atopic Sensitization in Children in Relation to
Measles Vaccination and Measles Infection” for conducting an interesting
study and highlighting numerous potential confounders in their report.
However, we wish to highlight several issues that warrant further
discussion.
The first issue is the disconnect between subjective outcome measures
“allergic symptoms” and “diagnosis of allergy by a physician” reported by
parents versus the objective measure of atopic sensitization. While the
authors point out that excluding children with history of wheezing and/or
eczema during the first year of life revealed an inverse association
between measles infection and subjective outcomes allergic
symptoms/diagnosis of allergy, they do not point out in their conclusions
the absence of association with respect to the objective outcome of atopic
sensitization. It is hard to attribute this to the decreased sample size,
as the odds ratios are close to 1 even in the higher IgE level group.
Additionally, the authors do a nice job of pointing out that the
prevalence of allergic disease was higher among Steiner children who
provided blood specimens versus Steiner children who did not provide blood
specimens, and adjust the analysis to determine the magnitude of this bias
(results not presented). We are concerned about another possible bias,
that due to the reference group and the group with measles being composed
mostly of Steiner-school children. Study group was included in the models
developed, but there is no mention of possible interaction between study
group and allergy symptoms or diagnosis, or whether interactions were
assessed in the models. The authors note a lack of heterogeneity in
results when the study groups were analyzed separately, but they present
no data. It would be helpful to the reader, in assessing the extent to
which Steiner-school children dominated the analysis, to have results
(including raw data) for symptoms/diagnosis and atopic sensitization
presented separately by study group.
Finally, we believe that the authors neglected to discuss the
critical issues of plausible mechanism and risk/benefit analysis of the
associations reported. If the underlying immune mechanism can be
simplified to a Th1 versus Th2 skew, it is plausible that measles
infection and to a lesser extent [live-attenuated] measles vaccination
protects from atopic disease, as suggested by the analysis of all children
with larger sample size. Regardless of whether measles vaccination is
less protective than measles infection or if measles infection alone is
protective against atopy, the risk of having measles infection versus the
risk of having asthma, eczema, and rhinoconjuntivitis should be considered
and discussed.
Sincerely,
Jakub Simon, M.D., M.S.
Pediatric Infectious Disease Specialist
Center for Vaccine Development
University of Maryland, Baltimore
William Blackwelder, Ph.D.
Biostatistician
Center for Vaccine Development
University of Maryland, Baltimore
Conflict of Interest:
None declared
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