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Free Content Does the efficacy of BCG decline with time since vaccination?

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Objective: To investigate whether the protective efficacy of bacille Calmette-Guérin (BCG) against tuberculosis decreases with time since vaccination.

Design: A quantitative review of all 10 randomized trials of BCG against tuberculosis in purified protein derivative (PPD)-negative individuals, that presented data for discrete periods. For each trial, we derived log rate ratios for the annual change in the efficacy of BCG. We also compared efficacy in the first two years, and the first 10 years, to that in the rest of the trial.

Results: There was considerable heterogeneity between trials in the annual change in the efficacy of BCG. In seven efficacy decreased over time, while in three it increased. Average annual change in efficacy was not related to overall efficacy. Efficacy also varied between trials in the first two years after vaccination, at more than two years after vaccination and in the first tent years after vaccination. However the variation in efficacy between trials more than 10 years after vaccination was not statistically significant (P = 0.26). We therefore calculated that the average efficacy more than 10 years after vaccination was 14% (95% confidence interval −9% to 32%).

Conclusion: BCG protection can wane with time since vaccination. There is no good evidence that BCG provides protection more than 10 years after vaccination.
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Keywords: BCG vaccine; meta-analysis; review; tuberculosis

Document Type: Regular Paper

Affiliations: 1: Department of Public Health Medicine, United Medical and Dental Schools, St. Thomas's Hospital, London, UK 2: Communicable Disease Epidemiology Unit, Department of Epidemiology and Population Sciences, London School of Hygiene and Tropical Medicine, London, UK

Publication date: March 1, 1998

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  • The International Journal of Tuberculosis and Lung Disease (IJTLD) is for clinical research and epidemiological studies on lung health, including articles on TB, TB-HIV and respiratory diseases such as COVID-19, asthma, COPD, child lung health and the hazards of tobacco and air pollution. Individuals and institutes can subscribe to the IJTLD online or in print – simply email us at [email protected] for details.

    The IJTLD is dedicated to understanding lung disease and to the dissemination of knowledge leading to better lung health. To allow us to share scientific research as rapidly as possible, the IJTLD is fast-tracking the publication of certain articles as preprints prior to their publication. Read fast-track articles.

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