Vitamin D Supplementation in TB Prevention

The goal of this clinical trial is to determine whether vitamin D supplementation reduces risk of acquiring latent tuberculosis infection (LTBI) in school age children in Mongolia. The investigators hypothesize that (1) vitamin D supplementation will reduce risk of acquisition of LTBI, (2) vitamin D supplementation will safely reduce risk of developing active TB and improve other secondary efficacy outcomes, and (3) children with the lowest vitamin D status at baseline will gain most from the intervention.