A retrospective longitudinal study of children in Manitoba, Canada reveals that childhood asthma is reduced by half when the first dose of diphtheria, pertussis (whooping cough) and tetanus (DPT) vaccination is delayed by more than two months.

The investigators analysed data from the complete immunisation and healthcare records of a cohort of children born in Manitoba in 1995, from birth until the age of seven. Using multivariable logistic regression, they computed the adjusted odds ratio for asthma at the age of seven according to the timing of DPT immunisation.

Among 11,531 children who received at least four 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 two months.

Further study is vital, researchers say, 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 immunisation programmes.

Source: J Allergy Clin Immunol. 2008;121:626-631
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First Published in June 2008

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