BCG Revaccination Fails to Protect Against Persistent Tuberculosis Infection

Recent research has demonstrated that revaccinating with Bacille Calmette-Guérin (BGC) does not effectively prevent long-term Mycobacterium tuberculosis infection. A comprehensive study, published in the New England Journal of Medicine, examined whether BCG revaccination could reduce the risk of sustained infection as measured by persistent changes in QuantiFERON-TB (QFT) test results.

The study was a phase 2b, double-blind, randomized trial involving 1,836 HIV-negative adolescents who initially tested negative on the QFT test. Participants were randomly assigned to receive either the BCG vaccine or a placebo. After 30 months, it was observed that the rate of sustained QFT conversion was similar between both groups, with no significant protective effect from revaccination. Specifically, 62 out of 871 individuals in the BCG group and 59 out of 849 in the placebo group showed persistent infection, resulting in a hazard ratio of 1.04 and a vaccine efficacy estimate of -3.8%.

While adverse reactions were more common among those who received the BCG vaccine—mostly injection site reactions—the immunological response indicated that BCG revaccination could induce cytokine-positive helper T cells. Nevertheless, these immune responses did not translate into protection against ongoing infection.

Based on these findings, researchers concluded that BCG revaccination is unlikely to confer protection against persistent tuberculosis infection. Although the vaccine induces certain immune responses, its failure to prevent sustained infection suggests it may not be effective in tuberculosis prevention strategies.

This study emphasizes the need for new or improved vaccines to combat tuberculosis, which remains a significant global health challenge.

Source: https://medicalxpress.com/news/2025-05-bcg-revaccination-sustained-mycobacterium-tuberculosis.html