Delaying DPT Vaccination May Reduce Incidence of Childhood Asthma

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http://www.medscape.com/viewarticle/572891

Delaying DPT Vaccination May Reduce Incidence of Childhood

Asthma CME News Author: Laurie Barclay, MD

CME Author: Laurie Barclay, MD

Disclosures

Release Date: April 14, 2008; Valid for credit through April

14, 2009

Authors and Disclosures

Laurie Barclay, MD

Disclosure: Laurie Barclay, MD, has disclosed no relevant financial

relationships.

Brande

Disclosure: Brande has disclosed no relevant financial

information.

April 14, 2008 ­ Childhood asthma is reduced by half when the first dose

of diphtheria, pertussis, and tetanus (DPT) is delayed by more than 2

months vs given during the recommended period, according to the results

of a retrospective longitudinal study reported in the March issue of the

Journal of Allergy & Clinical Immunology.

" Early childhood immunizations have been viewed as promoters of

asthma development by stimulating a

TH2-type immune response or decreasing

microbial pressure, which shifts the balance between

TH1 and TH2

immunity, " write Kara L. Mc, MSc, from the University of

Manitoba in Winnipeg, Manitoba, Canada, and colleagues. " Differing

time schedules for childhood immunizations may explain the discrepant

findings of an association with asthma reported in observational studies.

This research was undertaken to determine whether timing of diphtheria,

pertussis, tetanus (DPT) immunization has an effect on the development of

childhood asthma by age 7 years. "

The investigators analyzed data from the complete immunization and

healthcare records of a cohort of children born in Manitoba in 1995, from

birth until age 7 years. Using multivariable logistic regression, they

computed the adjusted odds ratio for asthma at age 7 years according to

the timing of DPT immunization.

Among 11,531 children who received at least 4 doses of DPT, the risk for

asthma was halved in children in whom administration of the first dose of

DPT was delayed by more than 2 months. For children with delays in

administration of all 3 doses, the likelihood of asthma was 0.39 (95%

confidence interval [CI], 0.18 - 0.86).

" We found a negative association between delay in administration of

the first dose of whole-cell DPT immunization in childhood and the

development of asthma; the association was greater with delays in all of

the first 3 doses, " the study authors write. " The mechanism for

this phenomenon requires further research. "

Limitations of this study include possible ascertainment bias; findings

not yet confirmed with the diphtheria, acellular pertussis, tetanus

(DaPT) vaccine; and inability to refute the issue of early-life

infections as an explanation for the association between delayed

immunization and protection against the development of asthma.

" Further study is vital to gain a detailed understanding of the

relationship between vaccination and allergic disease, because a

perception that vaccination is harmful may have an adverse effect on the

effectiveness of immunization programs, " the study authors

conclude.

The Canadian Institutes of Health Research supported this study. Some

of the authors have disclosed various financial relationships with the

Western Regional Training Center for Health Services Research, the

National Training Program in Allergy and Asthma, the Canadian Institutes

of Health Research, Allergen, and/or Novartis.

J Allergy Clin Immunol. 2008;121:626-631.

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Sheri Nakken, former R.N., MA, Hahnemannian

Homeopath

Vaccination Information & Choice Network, Nevada City CA & Wales

UK

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