Correspondence The Elusive Mechanistic Link between Exclusive Breast-

To the Editor—Several studies have shown an association between exclusive breast-feeding by human immunodefi-ciency virus (HIV)-infected African wom-en and a reduced rate of postnatal mother-to-child HIV transmission (MTCT) [1–4]. However, to date searches for a mechanism for this association have proved unsuc-cessful. In association with the first of these studies [1], we investigated what seemed the most obvious mechanism, that mixed feeding damaged the intestinal mucosa, fa-cilitating infection of the infant [5]. We found no evidence that this mechanism was correct. Subsequently, we [6–8] and, mor