Effectiveness of AZD7442 (Tixagevimab/Cilgavimab) for Pre-Exposure Prophylaxis Against COVID-19 Hospitalization in Israel During the Omicron Sub-Variant Time Period.

Introduction: The effectiveness of AZD7442 (tixagevimab/cilgavimab) against COVID-19 hospitalizations was determined at 3 and 6 months among immunocompromised individuals in Israel during different variant circulations.

Methods: This was a retrospective cohort study using data from Clalit Health Services in Israel. Immunocompromised individuals eligible to receive AZD7442 300 mg between 15 February and 11 December 2022 were identified. Immunocompromised individuals receiving AZD7442 300 mg as pre-exposure prophylaxis (PrEP) were propensity score (PS)-matched 1:1 to unexposed individuals using a "rolling cohort" approach. Calendar time Cox proportional hazards regression models were performed with adjustment for post-matched unbalanced covariates to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

Results: Overall, 2444 AZD7442-exposed immunocompromised individuals were PS-matched to unexposed individuals. In the matched population, up to 6 months of follow-up, AZD7442 300 mg presented an unadjusted HR (without adjustment for the unbalanced covariates) of 0.68 (95% CI 0.43-1.08) and covariate-adjusted HR of 0.64 (95% CI 0.40-1.03) against COVID-19 hospitalization. Covariate-adjusted instantaneous hazards plots showed that the effectiveness of AZD7442 300 mg waned from Day 90. Up to 3 months of follow-up, the unadjusted HR was 0.43 (95% CI 0.21-0.91) for AZD7442 300 mg against COVID-19 hospitalization in the matched population; there were insufficient events to allow covariate-adjusted analysis.

Conclusion: Our results suggest that AZD7442 300 mg reduced COVID-19 hospitalizations among immunocompromised individuals; however, the findings are limited by a lack of sufficient events to produce conclusive results.