Background WHO recommends isoniazid preventive therapy (IPT) for young children in close contact with an infectious tuberculosis (TB) case. No models have examined the cost effectiveness of this recommendation.

Methods A decision analysis model was developed to estimate health and economic outcomes of five TB infection screening strategies in young household contacts. In the no-testing strategy, children received IPT based on age and reported exposure. Other strategies included testing for infection with a tuberculin skin test (TST), interferon γ release assay (IGRA) or IGRA after TST. Markov modelling included age-specific disease states and probabilities while considering risk of re-infection in a high-burden country.

Results Among the 0–2-year-old cohort, the no-testing strategy was most cost effective. The discounted societal cost of care per life year saved ranged from US$237 (no-testing) to US$538 (IGRA only testing). Among the 3–5-year-old cohort, strategies employing an IGRA after a negative TST were most effective, but were associated with significant incremental cost (incremental cost-effectiveness ratio >US$233 000), depending on the rate of Mycobacterium tuberculosis infection.

Conclusion Screening for M tuberculosis infection and provision of IPT in young children is a highly cost-effective intervention. Screening without testing for M tuberculosis infection is the most cost-effective strategy in 0–2-year-old children and the preferred strategy in 3–5-year-old children. Lack of testing capacity should therefore not be a barrier to IPT delivery. These findings highlight the cost effectiveness of contact tracing and IPT delivery in young children exposed to TB in high-burden countries.