Why carry out this study?

Long-acting monoclonal antibodies may provide protection for individuals who respond suboptimally to coronavirus disease 2019 (COVID-19) vaccines and are at risk of severe disease, hospitalization, and death.

What did the study ask?

The PROVENT study assessed the efficacy and safety of pre-exposure prophylaxis with a single intramuscular injection of 300 mg AZD7442 (tixagevimab/cilgavimab) versus placebo in adults without prior severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection who were at appreciable risk of exposure to a SARS-CoV-2-infected individual and/or likely to respond suboptimally to vaccination.

The STORM CHASER study assessed the efficacy and safety of post-exposure prophylaxis with a single intramuscular injection of 300 mg AZD7442 versus placebo in adults without prior SARS-CoV-2 infection who had reported exposure to a SARS-CoV-2-infected individual in the previous 8 days, and were therefore at appreciable risk of developing COVID-19.

What was learned from the study?

The final 15-month analysis of the PROVENT study confirmed the efficacy of AZD7442 in reducing the risk of symptomatic COVID-19 over 6 months, and also suggested a reduction in severe and critical COVID-19 through 12 months.

The final 15-month analysis of STORM CHASER confirmed the findings of the primary analysis; although the study did not meet its primary efficacy endpoint of reducing symptomatic COVID-19 following post-exposure prophylaxis with AZD7442, a reduction in symptomatic COVID-19 was observed in participants who had SARS-CoV-2 reverse transcription-polymerase chain reaction status negative or missing at baseline.

In the final analysis of both trials, the overall safety profile of AZD7442 was consistent with that observed in previous studies with shorter follow-up time.

These analyses provide a proof of concept supporting the long-term safety of intramuscularly administered AZD7442 for the prevention of symptomatic and severe COVID-19.