A Cochrane review [Abstract] 2 included 51 studies with a total of 2871 subjects, each receiving on average 18 injections. Duration of immunotherapy varied from three days to three years. Symptom score data from 15 trials were suitable for meta-analysis and showed an overall reduction in the immunotherapy group (SMD -0.73; 95% CI -0.97 to -0.50, P < 0.00001; n=1063). Reduction was seen in nasal symptoms (SMD -1.59, 95% CI -2.28 to -0.89; 8 trials, n=633), ocular symptoms (SMD -1.80, 95% CI -3.28 to -0.31; 3 trials, n=345), and brochial symptoms (SMD -0.59, 95% CI -1.06 to -0.11; 5 trials, n=429). Medication score data from 13 trials showed an overall reduction in the immunotherapy group (SMD of -0.57 (95% CI -0.82 to -0.33, p<0.00001)). Clinical interpretation of the effect size is difficult. Adrenaline was given in 0.13% (19 of 14085 injections) of those on active treatment and in 0.01% (1 of 8278 injections) of the placebo group for treatment of adverse events. There were no fatalities.
A systematic review 1 including 43 rhinitis studies with a total of 2,001 subjects and 25 asthma studies with a total of 726 subjects was abstracted in DARE. Nine of thirteen studies on ragweed allergy and 14 of 15 studies on grass-pollen allergy proved efficacy. Six of nine studies on other pollen allergy proved efficacy. In the 43 rhinitis studies no efficacy was documented in 10 studies, low efficacy in 13 studies, moderate efficacy in 14 studies and high efficacy in 6 studies. The mean clinical improvement was a 45% reduction in symptom/medication score compared with placebo. The best results were obtained in grass-pollen allergy. Three of five studies on cat and/or dog immunotherapy documented a reduction in challenge test or improvement in exposure tests. The efficacy of immunotherapy in many studies was higher than for results obtained by antihistamines (one study) and equivalent to the reduction in clinical symptoms obtained by standard doses of intranasal or inhaled corticosteroids (7 studies).
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