Higher frequency of early local side effects with aqueous versus depot immunotherapy for hymenoptera venom allergy.

Venom immunotherapy has proven a very effective method for the treatment of allergy to Hymenoptera venom. Aqueous instead of depot extracts are prevalently used for this immunotherapy. The advantage of using aqueous extracts has not been fully investigated. We made an open, non-controlled study on 45 subjects sensitized to either Apis mellifera or Vespula spp. Patients were assigned to either a depot (N=27) or an aqueous (N=18) immunotherapy regimen, and side effects were monitored during the induction and the 3-year maintenance phase. The effect of naturally occurring stings during the treatment and after its interruption was recorded as well. Side effects were less frequent with the depot extract both on a "per patient" (22.2% versus 50.0%) and on a "per dose" (2.9% versus 10,2%) basis (p=0.026 and p<0.000, respectively). Better tolerance was mainly due to the lower frequency of local side effects occurring at early times after vaccination. The efficacy of vaccination was comparable in the 2 cohorts, as expected. We conclude that depot immunotherapy to Hymenoptera venom should be preferred to aqueous immunotherapy for the lower occurrence of local side effects. This might influence a better compliance with this potentially life-saving treatment.