Objectives: The impact of large-dose vitamin A supplementation given at intervals of 4 months on child mortality and morbidity was examined according to the time interval since dosing, number of doses received previously, and time of year.
Methods: Two double-blind, randomized, placebo-controlled trials of large doses of vitamin A administered at intervals of 4 months were conducted in adjacent populations in northern Ghana.
Results: While vitamin A supplementation significantly reduced the overall incidence of severe illnesses (especially diarrhea with dehydration), clinic attendances, hospital admissions, and mortality, there was no evidence that the impact of each dose of vitamin A was related to the number of doses the child had received previously. There was no evidence that the effectiveness of the supplement waned over the 3 to 5 months between doses. The impact on mortality did not differ significantly by the month in which the supplement had been given.
Conclusions: In the study population, there was no evidence that an interval between doses of less than 4 months would have had a greater impact on severe morbidity or mortality, and the effectiveness of supplementation did not vary by time of year.