BACKGROUND: Vitamin D deficiency is associated with progression of latent tuberculosis (TB) infection to active disease. The impact of preventive therapy on this association is unknown.METHOD: Serum 25-hydroxyvitamin D (25(OH)D) levels were retrospectively linked to adults diagnosed with latent TB between April 2010 and January 2019 in a hospital in London, UK. Individuals in the cohort who progressed to active TB were identified by matching to a national notification register. A logistic regression model was used to examine baseline vitamin D deficiency and use of preventive therapy with subsequent incidence of TB disease.RESULTS: Of 1509 latently infected individuals with 3902 patient-years of follow-up, 687 (45.5%) were identified as vitamin D deficient and 691 (45.8%) individuals had a LTBI regimen prescribed. There were 29 (1.9%) instances of TB reactivation. On multivariate analysis, profound (<25 nmol/L) vitamin D deficiency (aHR 5.68, 95%CI 2.18-14.82; P = 0.0003) and the absence of preventive therapy (aHR 3.84, 95%CI 1.46-10.08; P = 0.006) were associated with progression to active TB disease. There was no evidence that preventive therapy modified the association between vitamin D status and TB reactivation.CONCLUSION: Our results show an independent association between vitamin D deficiency and progression from latent TB infection to active disease.