Novel 4-day outpatient Hymenoptera venom immunotherapy buildup protocol with low reaction rates

Hymenoptera stings can cause severe systemic reactions, including life-threatening anaphylaxis. Venom immunotherapy (VIT) remains the only disease-modifying treatment for Hymenoptera venom allergy. Conventional outpatient VIT buildup protocols are safe and well-tolerated but require prolonged buildup phases. In contrast, accelerated inpatient rush and ultrarush protocols are associated with higher costs due to inpatient hospitalization and may increase the risk of systemic reactions.

To evaluate the safety and efficacy of a novel 4-day outpatient VIT buildup protocol compared with established inpatient rush and ultrarush regimens.

In this retrospective, single-center cohort study, 566 VIT treatments (560 patients) with bee or vespid venom were analyzed. Patients received a 4-day outpatient (n = 363), an inpatient 3-day rush (n = 118), or an inpatient 2-day ultrarush (n = 85) buildup protocol. The primary outcome was the incidence of systemic allergic reactions requiring emergency intervention during buildup. Uni- and multivariable logistic regression was performed to identify factors associated with this outcome.

The novel outpatient protocol showed a lower rate of systemic reactions requiring emergency intervention (4.4%) than did the rush (9.3%) and ultrarush (12.9%) protocols. Multivariable analysis confirmed that use of the novel outpatient protocol independently reduced the risk of systemic reactions (odds ratio 0.33; 95% CI 0.17-0.66; P = .002). Maintenance VIT was well-tolerated across all 3 protocols, with a low incidence of systemic allergic reactions.

We report a novel 4-day outpatient VIT protocol that offers a rapid, safe, and accessible alternative to resource-intensive inpatient regimens. Prospective studies are required to confirm long-term efficacy and broader applicability.