Background53Basic science, epidemiological and interventional research supports a link between vitamin D and 54tuberculosis immunity, infection and disease. We evaluated the association between vitamin D 55levels and tuberculosis (TB) infection and disease in UK children recruited to the NIHR IGRA Kids 56Study (NIKS).57Methods58Children presenting between 2011-2014 were eligible if they had history of exposure to an adult 59case with sputum smear/culture-positive TB, or were referred and diagnosed with TB disease. 60Children were assessed at baseline and 6-8 weeks for immunological evidence of TB infection (IGRA 61and/or tuberculin skin test) and evidence of TB disease. Some centres routinely measured total 25-62hydroxy vitamin D levels.63Results64166 children were included. Median 25-hydroxy vitamin D levels were higher in uninfected children 65(45.5 nmol/l) compared to those with infection (36.2 nmol/l) and disease (20.0 nmol/l). The 66difference between TB infection and disease was statistically significant (p<0.001). By logistic 67regression, lower vitamin D levels were associated with TB disease among participants with 68infection/disease, with no evidence of confounding by age, sex, BCG status, ethnicity, non-contact 69referral, season or centre.70Conclusion71Children with TB disease had lower vitamin D levels than children with infection. Implications for 72prevention and treatment remain to be established.