Background Tuberculosis (TB) control requires the understanding and disruption of TB transmission. We describe prevalence, incidence and risk factors associated with childhood TB infection in Cape Town.

Methods We report cross-sectional baseline and prospective incidence data from a large trial among primary school children living in high TB-burden communities. Prevalent infection was defined as QuantiFERON-TB Gold Plus (QFT-Plus) positivity as assessed at baseline. Subsequent conversion to QFT-Plus positivity was measured 3 years later among those QFT-Plus-negative at baseline. Multivariable logistic regression models examined factors associated with TB infection.

Results QuantiFERON-positivity at baseline (prevalence: 22.6%, 95% Confidence Interval [CI]: 20.9 – 24.4), was independently associated with increasing age (adjusted odds ratio [aOR] 1.24 per additional year, 95% CI: 1.15 – 1.34) and household exposure to TB during the participant’s lifetime (aOR 1.87, 95% CI: 1.46 – 2.40). QFT-Plus conversion at year 3 (12.2%, 95% CI: 10.5-14.0; annual infection rate: 3.95%) was associated with household exposure to an index TB case (aOR 2.74, 95% CI: 1.05 to 7.18).

Conclusion Rates of QFT-diagnosed TB infection remain high in this population. The strong association with household TB exposure reinforces the importance of contact tracing, preventative treatment and early treatment of infectious disease to reduce community transmission.

ARM declares receipt of funding in the last 36 months to support vitamin D research from the following companies who manufacture or sell vitamin D supplements: Pharma Nord Ltd, DSM Nutritional Products Ltd, Thornton & Ross Ltd and Hyphens Pharma Ltd. ARM also declares receipt of vitamin D capsules for clinical trial use from Pharma Nord Ltd, Synergy Biologics Ltd and Cytoplan Ltd; support for attending meetings from Pharma Nord Ltd and Abiogen Pharma Ltd; receipt of consultancy fees from DSM Nutritional Products Ltd and Qiagen Ltd; receipt of a speaker fee from the Linus Pauling Institute; participation on Data and Safety Monitoring Boards for the VITALITY trial (Vitamin D for Adolescents with HIV to reduce musculoskeletal morbidity and immunopathology, Pan African Clinical Trials Registry ref PACTR20200989766029) and the Trial of Vitamin D and Zinc Supplementation for Improving Treatment Outcomes Among COVID-19 Patients in India (ClinicalTrials.gov ref NCT04641195); and unpaid work as a Programme Committee member for the Vitamin D Workshop. All other authors declare that they have no competing interests.

NCT02880982

This research was funded by the UK Medical Research Council (refs MR/R023050/1 and MR/M026639/1, both awarded to ARM). RJW was supported by Wellcome (104803, 203135). He also receives support from the Francis Crick Institute which is funded by Cancer Research UK (FC2112), the UK Medical Research Council (FC2112) and Wellcome (FC2112).

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Ethics committee/IRB of University of Cape Town Faculty of Health Sciences gave ethical approval for this work Observational/Interventions Research Ethics committee/IRB of London School of Hygiene and Tropical Medicine gave ethical approval for this work

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