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INTRODUCTION: A more effective tuberculosis (TB) vaccine is needed to eliminate TB disease. Many new vaccine candidates enhance the immunogenicity of the existing vaccine, Bacillus Calmette-Guérin (BCG). Understanding BCG induced immune variation is key to developing a new vaccine. AIMS: We aimed to establish if individual-level covariates were associated with cell-mediated immune response (interferon gamma (IFN-γ)) at vaccine trial enrolment (baseline) in a long-term retrospective analysis (LTR) and after BCG vaccination in a short-term prospective analysis (STP). METHODS: Four covariates were analysed: gender, country, BCG vaccination history and monocyte/lymphocyte cell count ratio. Univariable and multivariable linear regression were conducted on IFN-γ response at baseline for LTR, and area under the curve (AUC), 24 week and peak IFN-γ response for STP. RESULTS: Previous BCG vaccination was strongly associated with higher IFN-γ response at baseline (LTR analysis) (p-values < 0.05). Being male showed a weak association with higher baseline response (p-value = 0.1). BCG revaccination was strongly associated with a larger response increase than primary-vaccination (AUC & peak p-values < 0.01), but did not differ at 24 weeks (STP analysis). All other covariates were non-significant (p-values > 0.1). CONCLUSION: This analysis suggests that previous BCG vaccination and gender are associated with durable IFN-γ responses. Vaccine trials may need to stratify by BCG vaccination history and gender.

Original publication




Journal article


Tuberculosis (Edinb)

Publication Date





37 - 43


BCG, IFN-γ, Immune response, Tuberculosis, Adolescent, Adult, Area Under Curve, BCG Vaccine, Biomarkers, Cross-Sectional Studies, Enzyme-Linked Immunospot Assay, Female, Humans, Immunity, Cellular, Immunization Schedule, Interferon-gamma, Interferon-gamma Release Tests, Linear Models, Male, Middle Aged, Multivariate Analysis, Mycobacterium tuberculosis, Predictive Value of Tests, Prospective Studies, ROC Curve, Retrospective Studies, Sex Factors, Time Factors, Vaccination, Young Adult