https://www.nejm.org/doi/full/10.1056/NEJMoa2109682
an excerpt:
Among household members who were confirmed to be both uninfected and without a recent history of infection, subcutaneous REGEN-COV prevented both symptomatic and overall SARS-CoV-2 infections, and the majority of participants who received this agent had minor or no adverse events. The relative risk reduction between the REGEN-COV group and the placebo group in the incidence of symptomatic SARS-CoV-2 infection was approximately 81%. Within 1 week after the initiation of REGEN-COV or placebo, the relative risk reduction was approximately 72%, which increased to approximately 93% after the first week. The relative risk reduction in high-viral-load infections (>104 copies per milliliter) was approximately 86%, and the relative risk reduction in all infections (symptomatic and asymptomatic) was approximately 66%. In participants in whom SARS-CoV-2 infection developed, those in the REGEN-COV group had a lower likelihood of symptoms than those in the placebo group. In the participants who became infected after receiving REGEN-COV or placebo and in whom symptomatic infection was confirmed, the duration of symptoms was 2 weeks shorter in the REGEN-COV group (in whom laboratory-confirmed symptomatic infection developed in 1.5%) than in the placebo group. Moreover, in participants in whom either symptomatic or asymptomatic infection developed, the magnitude and duration of detectable RNA (i.e., the peak viral load and weeks of RT-