Vitamin D Earns More than a Passing Grade

respiratory tract infections and pneumonia [4]. In this issue of the Journal, Mehta and colleagues [5] present data suggesting that infants born to human immunodeficiency virus (HIV)‐infected women with low vitamin D levels have an increased risk of acquiring HIV infection at each of the following stages: in utero, intrapartum, and during breast-feeding. In addition, HIVinfected mothers with low vitamin D levels and their infants, regardless of HIV status, are more likely to die than are those with adequate levels of vitamin D. At first glance, these data might be dismissed. Previous studies by this group of investigators were predominantly designed to investigate the benefits of multivitamin supplements and vitamin A on mother-to-child transmission (MTCT) of HIV as well as on maternal and child outcomes in Tanzania [6, 7]. The assessment of vitamin D levels was part of a secondary study and surely will need to be confirmed by other investigators. However, are these results biologically plausible? Having become a recent convert to believing in the benefits of vitamin D, I would argue that the data presented are not only plausible but provide insight into a potential approach to improving the outcomes of children born