Vaccines against the SARS-CoV-2 virus were authorized for use by the Food and Drug Administration (FDA) in the United States and have proven effective for the prevention of morbidity and death from COVID-19. Certain immunosuppressant medications prevent the development of protective immunity following COVID-19 vaccination. In December 2021, the FDA issued an emergency use authorization (EUA) for a monoclonal-antibody combination of tixagevimab and cilgavimab, under the brand name Evusheld, for pre-exposure prophylaxis (PrEP) against COVID-19 for individuals with moderate-to-severe immune compromise. While a 77% reduction in symptomatic COVID-19 was observed in the PROVENT study, the trial was conducted prior to emergence of the B.1.1.529 Omicron variant. We suspected reduced efficacy of PrEP against Omicron subvariants. We conducted a retrospective cohort study comparing the prevalence of symptomatic COVID-19 infections between 1 January 2022 and 1 July 2022 in eligible patients treated with PrEP versus untreated using a questionnaire administered with the REDCap survey tool. Responses from 235 participants were included in the final analysis, with 176 untreated respondents and 59 in the PrEP cohort. Symptomatic COVID-19 infections were reported in 50 (28.4%) untreated participants and only 9 (15.3%) of those who received PrEP (p = 0.0557; OR 0.4536; 95% CI 0.2046 to 0.9599). Only two participants were hospitalized for COVID-19 infection, both in the untreated cohort. The reduction in COVID-19 infections did not achieve statistical significance, indicating diminished efficacy against Omicron variants.
Keywords: COVID-19; Omicron; cilgavimab; multiple sclerosis; tixagevimab.