2439. The role of positive externalities in economic evaluations of new antibiotics: modeling the impact of reduced transmission in healthcare facilities

BACKGROUND: Positive externalities - beneficial spillover effects enjoyed by individuals who are not the primary consumers of a good - are rarely considered in cost-effectiveness analyses (CEAs) of antimicrobial drugs that could reduce person-to-person transmission of the target pathogen. We developed a compartmental model to simulate the effect of 2 hypothetical antibiotics targeting carbapenem-resistant Enterobacteriaceae (CRE) among hospital inpatients: one that treats bloodstream infections (BSIs) and one that decolonizes carriers. We assessed the contribution of positive externalities to the results of CEAs of these 2 antibiotics in the model. METHODS: Our model tracked patients according to CRE carriage, clinical infection, and detection status. Rates of CRE acquisition depended on transmissibility of carriers in different states and were calibrated to data from long-term acute care hospitals. For the BSI treatment scenario we assumed the new drug would decrease the death rate and transmissibility of patients after CRE BSI onset. For the decolonization scenario we assumed the new drug would increase clearance of CRE carriage after clinical detection. For each scenario, we quantified the drug’s effect on the number of BSIs and deaths among patients receiving the drug (direct effect) and among all patients (total effect, i.e., direct plus indirect effect) compared with usual care. For the CEAs, the effectiveness outcome was life-years (LYs) gained and we assumed the new drug cost of $4,000 per dose and cost of a CRE BSI of $24,788. RESULTS: For both the BSI treatment and decolonization scenarios, the total effect of introducing the new drug was greater than the direct effect alone, indicating the existence of positive externalities. Relative to usual care, the new drug led to a decrease in incremental cost and an increase in incremental effectiveness (see Figures 1 and 2). CONCLUSION: The inclusion of positive externalities in CEAs can have important effects on whether these new antibiotics are deemed cost-effective, due to their potential for interrupting chains of transmission. In our model, the inclusion of these effects reduced the incremental cost and increased the incremental effectiveness of these antibiotics. [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.