Infusion of a broadly neutralizing antibody (bnAb) does not prevent overall HIV-1 acquisition more effectively than placebo, according to a study of two trials published in the New England Journal of Medicine. Researchers randomly assigned 2,699 at-risk cisgender men and transgender persons in the Americas and Europe in the HVTN 704/HPTN 085 trial and 1,924 at-risk women in sub-Saharan Africa in the HVTN 703/HPTN 081 trial to receive either infusions of a bnAb (VRC01; low dose [10 mg/ kg] or high dose [30 mg/kg]) or placebo for 10 infusions. Within each trial, adverse events were similar in number and severity among the treatment groups. In the HVTN 704/HPTN 085 trial, the incidence rates of HIV-1 infection were 2.35 and 2.98 per 100 person-years in the pooled VRC01 groups and the placebo group, respectively (estimated prevention efficacy, 26.6%; 95% confidence interval [CI], −11.7 to 51.8; P = 0.15); in the HVTN 703/HPTN 081 group, the corresponding incidence rates were 2.49 and 3.10 (estimated prevention efficacy, 8.8%; 95% CI, −45.1 to 42.6; P = 0.70). In prespecified analyses pooling data across trials, the incidence rates of infection with VRC01- sensitive isolates were 0.20 and 0.86 per 100 person-years among VRC01 and placebo recipients, respectively (estimated prevention efficacy, 75.4%; 95% CI, 45.5 to 88.9)