Moreover, because vitamin A and iron have important roles in
the immune system [38–40] and the supplementation markedly
increased the vitamin A and iron status of the preschool children
[19], it appears likely that vitamin A and iron fortification also
contributed to the lower morbidity, although the comparison of
a synergistic interaction and/or combined effect of vitamin A and
iron to the solitary effect on the immune function needs more
clarification.
We believe that this randomized