This study was done to investigate Vespula VIT clinical efficacy after discontinuation and the kinetics of Vespula-specific IgE and IgG4. 686 consecutive patients we retrospectively selected and analysed a series of 23 patients with Vespula allergy that underwent a IT course, followed by a prolonged follow-up.

Clinical efficacy of VIT was assessed as number and severity of reactions to Vespula re-stinging events. The Vespula-specific IgE and IgG4 was also monitored over time.

Patients were protected, reporting no reactions or mild reactions in occasion of re-stinging events during the treatment. Protection was maintained during the follow-up, up to 8 years. Skin reactivity and circulating Vespula-specific IgE levels declined substantially. Notably, this reduction was maintained over time during the follow-up. All the patients were analysed for IgG4. A robust induction of Vespula-specific IgG4 was observed during the VIT course.

The study concluded through its findings that Vespula VIT is a clinically effective treatment, which induces long-term protection after discontinuation. The reduction of specific IgE, assessed by skin tests and RAST, closely matches the VIT- induced protection, while the IgG4 induction seems not to be associated with VIT clinical efficacy in the long term.