BACKGROUND: There is a need to establish the effectiveness, cost-effectiveness and safety of allergen immunotherapy (AIT) for the prevention of allergic disease.
METHODS: Two reviewers independently screened nine international biomedical databases. Studies were quantitatively synthesized using random-effects meta-analyses.
RESULTS: 32 studies satisfied the inclusion criteria. Overall, meta-analysis found no conclusive evidence that AIT reduced the risk of developing a first allergic disease over the short-term (RR=0.30; 95%CI 0.04 to 2.09) and no randomized controlled evidence was found in relation to its longer-term effects for this outcome. There was however a reduction in the short-term risk of those with allergic rhinitis developing asthma (RR=0.40; 95%CI 0.29 to 0.54), with this finding being robust to a pre-specified sensitivity analysis. We found inconclusive evidence that this benefit was maintained over the longer-term: RR=0.62; 95%CI 0.31 to 1.23. There was evidence that the risk of new sensitization was reduced over the short-term, but this was not confirmed in the sensitivity analysis: RR=0.72; 95%CI 0.24 to 2.18. There was no clear evidence of any longer-term reduction in the risk of sensitization: RR=0.47; 95%CI 0.08 to 2.77. AIT appeared to have an acceptable side-effect profile.
CONCLUSIONS: AIT did not result in a statistically significant reduction in the risk of developing a first allergic disease. There was however evidence of a reduced short-term risk of developing asthma in those with allergic rhinitis, but it is unclear whether this benefit was maintained over the longer-term. We are unable to comment on the cost-effectiveness of AIT. This article is protected by copyright. All rights reserved.