In this issue of the Journal, the report by Banerjee et al. [1] on the postneonatal protective effect of a prior neonatal infection with G10P [11] rotavirus has important implications for rotavirus vaccinology. The protective efficacy of a neonatal rotavirus infection has been addressed previously by various investigators. In a 1983 Australian study, neonates with asymptomatic rotavirus shedding during the first 14 days of life developed fewer and lesssevere rotavirus-positive diarrhealillnesses postneonatally than did control children [2]. The available strains causing neonatal infection had identical electrophoretic patterns (in addition, 1 strain was identified as an "M-like" [G3] strain [3, 4]), whereas the strains causing postneonatal infection had varying patterns. Although serotypic characterization was not readily available at the time, evidence now indicates that asymptomatic neonatal G3 infections pro-