WITHDRAWN Cost-Utility Analysis of Tixagevimab and Cilgavimab for Pre-Exposure Prophylaxis of COVID-19 in Costa Rica

OBJECTIVES: Immunocompromised people who cannot be vaccinated against COVID-19 remain at risk for severe disease. Tixagevimab and cilgavimab are monoclonal antibodies obtained from persons infected with SARS-CoV-2. Therefore, the cost-utility ratio of tixagevimab and cilgavimab was evaluated in people with primary and secondary immunodeficiencies to prevent COVID-19.

METHODS: Model structures are a decision tree during the acute phase (29 days) and a Markov model for the post-acute phase. In the acute phase, tixagevimab and cilgavimab were compared vs. standard of care (SoC). During the acute phase, infected people have five options to be treated: ambulatory, hospitalized without oxygen, hospitalized with low flow oxygen, hospitalized with non-invasive ventilation, and hospitalized with mechanical ventilation or extracorporeal membrane oxygenation. Patients could recover, suffer long COVID, or die in every outcome. Patients with long COVID move to a Markov model that presents three stages: long COVID, recovery, or death. The time horizon for long-term outcomes is a life with an expectancy of 33,2 years after entering the model. Costs and healthcare values were discounted by 3.5%; efficacy was based on the pivotal clinical trial. An advisory board estimated direct and indirect healthcare costs; this ad-board included intensivists, internists, pulmonologists, cardiologists, and neurologists from Costa Rica. The willingness-to-Pay (WTP) threshold was three times the gross domestic product per capita (USD 36,230).

RESULTS: In a cohort of 1,000 patients, tixagevimab and cilgavimab avoided 99 cases of COVID-19, 54 long-COVID cases, five deaths, and saved 377 bed days vs. SoC, as well as providing 672 more Quality-Adjusted-Life-Years (QALYs) and 61.5 life-years more than SoC. The incremental cost-effectiveness ratio is USD 1,993 per QALY gained; tixagevimab and cilgavimab have a 100 % probability of being the best therapeutic option vs. SoC.

CONCLUSIONS: Tixagevimab/cilgavimab is a highly cost-effective option to prevent COVID-19 in patients with immunodeficiencies in Costa Rica.