Does BCG vaccination reduce the risk of childhood asthma?

Published Online: September 30, 2013

Allergic asthma is very common in children and young people. BCG vaccination has the potential to modulate the developing immune system and research has suggested that this may be a possible preventive strategy for childhood asthma. Previous studies have however yielded conflicting results.

One such study, published in The Journal of Allergy and Clinical Immunology (JACI) in 2007, was the Manchester Community Asthma Study (MANCAS), which investigated this phenomenon in a cohort of young children born in an area of the UK where there was a vaccine dosing error and as a result neonatal BCG vaccination policy changed twice within a short timeframe. This work demonstrated a significantly lower prevalence of wheeze for children given neonatal BCG vaccination and this finding was supported in a subsequent JACI publication of a systematic review and meta-analysis, carried out in collaboration between researchers from the MANCAS team and The University of Edinburgh.

In a recent issue of the JACI, Linehan et al. now report the findings of the second phase of the MANCAS study (MANCAS 2) where they investigated if any protective effects of BCG vaccination extended into adolescence. The researchers analyzed the association between evidence of BCG vaccination as recorded on a health records database and parent reported wheeze. The researchers then updated their systematic review to identify any other relevant recent studies and then synthesized this evidence with data from MANCAS 2 in an updated meta-analysis.

MANCAS 2 did not identify any difference in the prevalence of wheeze between those with and without BCG vaccination. The updated meta-analysis which included data from MANCAS 2 and 3 additional studies indicated that any protective effect of BCG vaccination on the risk of developing asthma is likely to be only transient.

Taken together, the results of MANCAS2 and the updated meta-analysis provide the clearest evidence yet that BCG vaccination is unlikely to have any lasting or long-term effects on the risk of children developing allergic asthma.

The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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