Author:
Trauer James M,Kawai Andrew,Coussens Anna K,Datta Manjula,Williams Bridget M,McBryde Emma S,Ragonnet Romain
Abstract
RationaleThe heterogeneity in efficacy observed in studies of BCG vaccination is not fully explained by currently accepted hypotheses, such as latitudinal gradient in non-tuberculous mycobacteria exposure.MethodsWe updated previous systematic reviews of the effectiveness of BCG vaccination to 31 December 2020. We employed an identical search strategy and inclusion/exclusion criteria to these earlier reviews, but reclassified several studies, developed an alternative classification system and considered study demography, diagnostic approach and tuberculosis (TB)-related epidemiological context.Main resultsOf 21 included trials, those recruiting neonates and children aged under 5 were consistent in demonstrating considerable protection against TB for several years. Trials in high-burden settings with shorter follow-up also showed considerable protection, as did most trials in settings of declining burden with longer follow-up. However, the few trials performed in high-burden settings with longer follow-up showed no protection, sometimes with higher case rates in the vaccinated than the controls in the later follow-up period.ConclusionsThe most plausible explanatory hypothesis for these results is that BCG protects against TB that results from exposure shortly after vaccination. However, we found no evidence of protection when exposure occurs later from vaccination, which would be of greater importance in trials in high-burden settings with longer follow-up. In settings of declining burden, most exposure occurs shortly following vaccination and the sustained protection observed for many years thereafter represents continued protection against this early exposure. By contrast, in settings of continued intense transmission, initial protection subsequently declines with repeated exposure to Mycobacterium tuberculosis or other pathogens.
Funder
National Health and Medical Research Council
Subject
Pulmonary and Respiratory Medicine
Reference61 articles.
1. World Health Organization . Global tuberculosis report 2019, 2019.
2. World Health Organization . World immunization profile, 2020. Available: http://www.who.int/immunization/monitoring_surveillance/data/gs_gloprofile.pdf?ua=1
3. The efficacy of Bacillus Calmette-Guérin vaccination of newborns and infants in the prevention of tuberculosis: meta-analyses of the published literature;Colditz;Pediatrics,1995
4. Protection by BCG Vaccine Against Tuberculosis: A Systematic Review of Randomized Controlled Trials
5. Systematic review and meta-analysis of the current evidence on the duration of protection by Bacillus Calmette-Guérin vaccination against tuberculosis;Abubakar;Heal Technol Assess,2013
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