When is research on children ethical?

Is it ever ethical to do research on human subjects without their consent? The Nuremberg Code, written in the aftermath of the atrocities perpetrated by Nazi doctors, makes the voluntary consent of the human subject “absolutely essential”. Understandable as the desire for so absolute a barrier may be, it comes at a high cost, for it blocks research with the potential to help many children. Hence in 1964 the World Medical Association, in the Declaration of Helsinki, took a different stance, allowing research on human beings without the capacity to consent, if consent can be obtained from a legally authorised representative.