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You are working on the postnatal ward of a busy maternity hospital. While doing a routine discharge check of a newborn baby, the mother asks you about the availability of BCG vaccination. Her two older children have severe eczema, asthma and food allergies, and she has read on the internet that BCG may reduce the risk of allergic disease.
Structured clinical question
In a newborn infant (patient), does BCG vaccination (intervention) prevent the development of allergic disease in later life (outcome)?
Search strategy and outcome
Medline and Embase were searched (1946 to current date) using the keywords ((bacille Calmette-Guérin) OR (BCG)) AND (allergy OR asthma). Restrictions were human subjects, randomised controlled trials, systematic reviews and meta-analyses. This search yielded 64 articles. A search of the Cochrane Library revealed a further five articles. Of these 69 articles, one randomised controlled trial and four systematic reviews (three with meta-analyses) of observational studies were relevant and selected for full text review. Excluded articles included 10 randomised controlled trials of BCG as an immune therapy for asthma and allergic rhinitis in childhood as they did not relate to the question of prevention.
The hygiene hypothesis proposes that diminished microbial exposure in early life prevents the switch from the T helper 2 (Th2) immune response that predominates in neonates to a T helper 1 (Th1) response.1 A persistent …