With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: The use of vitamin A during treatment is recommended to decrease the risk of blindness; however, it does not prevent or cure the disease. A systematic review of trials into its use found no reduction in overall mortality, but two doses (200 000 IU) of vitamin A was shown to reduce mortality for measles in children younger than two years of age. Zinc supplementation in children with measles has been shown to affect outcomes in some studies, but is unclear to what extent as it has not been sufficiently studied. There are no adequate studies on whether Chinese medicinal herbs are effective.
text_B: Can a researcher find enough studies that show the efficacy of zinc supplementation in children with measles?
NO.