Mass drug administration (MDA) of azithromycin to children aged 1–59 months reduced infant (1–11 months) mortality by 23% compared to placebo.
Adding azithromycin treatment for older siblings (12–59 months) provided an incremental mortality reduction among infants beyond direct treatment alone.
Spillover benefits from treating siblings accounted for roughly three-quarters of the observed mortality reduction.
Although the interaction between sibling treatment and infant mortality was not statistically significant, there was a trend toward lower mortality in infants living with treated older siblings.
