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.
Keywords: BCG; IFN-γ; Immune response; Tuberculosis.
Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.