D3.424 - Long-term efficacy and re-sting outcomes following venom immunotherapy discontinuation: A 978-patient analysis

This retrospective study evaluates the long-term efficacy of VIT after cessation, observing reactions to re-stings in 687 patients 3-23 years post a 5-year VIT regimen. 

Analysing data from 2217 identified patients who underwent VIT between 1995 and 2020, 1049 responded, leaving 978 after exclusions. We assessed re-sting reactions in 383 BVIT and 671 WVIT recipients, some treated for both. Reactions were graded by severity; emergency kit use post-VIT was tracked. Reaction rates post-re-sting were compared using the two-proportion Z-test. Relatives of 164 deceased patients were contacted to identify insect sting-related deaths, 64 responded with 1 confirmed sting-related death. 

687 (71.9%) reported re-stings during a follow-up period of 3-23 years post-treatment. Systemic allergic reactions were observed in 25.5% of re-stung BVIT patients and 15.5% of WVIT patients, with severe reactions in 11.3% and 5.3%, respectively. Hornet stings post-WVIT led to SARs in 29.5% of cases, with severe reactions in 15.9%. Statistical analysis revealed significant differences in the rates of systemic and severe reactions between BVIT and WVIT groups. Additionally, 13.3% of bee and 10.4% of wasp VIT recipients continued to carry auto-injectors post-VIT. 

This study provides insights into the long-term efficacy of VIT up to 23 years post- treatment, with a significant portion of patients experiencing re-stings. There was a slight expected increase in systemic allergic reactions compared to the frequency observed at the end of VIT treatment, with WVIT proving more effective than BVIT. Additionally, WVIT offers somewhat effective protection against hornet stings.