Bacille Calmette-Guérin, or BCG, vaccination is associated with a lower prevalence of latent tuberculosis infection in adult TB contacts and could protect against Mycobacterium tuberculosis infection, according to results published in Journal of Infectious Diseases.
TB is the leading cause of death from infectious disease worldwide, according to Anthea L. Katelaris, BMed, MD, MSc(dist), faculty of public health and policy at the London School of Hygiene and Tropical Medicine, and colleagues. The BCG vaccine, which is widely used, is the only licensed vaccine against Mycobacterium tuberculosis (Mtb).
“Infant BCG vaccination has shown consistently high efficacy of 70% to 80% against childhood TB, namely meningitis and miliary TB,” the researchers wrote. “The protective effect of BCG against adult pulmonary disease varies geographically, which may in part be associated with varying exposure to Mtb or environmental mycobacteria, which may mask or block protection induced by BCG.”
To determine whether BCG vaccination is associated with decreased prevalence of Mtb infection in adults, Katelaris and colleagues conducted a cross-sectional analysis of data from adult contacts of TB cases participating in the U.K. PREDICT study, a prospective cohort study that aimed to assess the prognostic value of interferon-gamma release assays in predicting the development of active TB among individuals with or at risk of latent TB infection (LTBI). Researchers assessed vaccine effectiveness of BCG against LTBI based on the presence of a scar or vaccination history using multivariable logistic regression and explored the effects of age at BCG vaccination and time since vaccination.
In total, 3,453 recent TB contacts from the PREDICT study were eligible for inclusion. Of these, 27.5% had LTBI. There was strong evidence of an association between BCG and LTBI ( adjusted OR = 0.70; 95% CI, 0.56-0.87), yielding vaccine effectiveness of 30%. In addition, although vaccine effectiveness declined with time, the researchers found evidence that LTBI prevalence was lower in vaccinated individuals compared with nonvaccinated participants, even when 20 years had passed since vaccination.
“Our study contributes to the growing evidence that suggests BCG can act partially by providing protection against Mtb infection as well as disease,” the authors concluded. “This has important implications for immunization programs, vaccine development and assessment, and TB control efforts worldwide.” – by Caitlyn Stulpin
Disclosures: Katelaris reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.