Background: Evidence of protection from childhood Bacillus Calmette-Guerin (BCG) against tuberculosis (TB) in adulthood, when most transmission occurs, is important for TB control and resource allocation. Methods: We conducted a population-based case-control study of protection by BCG given to children aged 12-13 years against tuberculosis occurring 10-29 years later. We recruited UK-born White subjects with tuberculosis and randomly sampled White community controls. Hazard ratios and 95% confidence intervals (CIs) were estimated using case-cohort Cox regression, adjusting for potential confounding factors, including socioeconomic status, smoking, drug use, prison and homelessness. Vaccine effectiveness (VE=1 - hazard ratio) was assessed at successive intervals more than 10 years following vaccination. Results: We obtained 677 cases and 1170 controls after a 65% response rate in both groups. Confounding by deprivation, education and lifestyle factors was slight 10-20 years after vaccination, and more evident after 20 years. VE 10-15 years after vaccination was 51% (95% CI 21, 69%) and 57% (CI 33, 72%) at 15-20 years. Subsequently, BCG protection appeared to wane; 20-25 years VE=25% (CI -14%, 51%) and 25-29 years VE=1% (CI -84%, 47%). Based on multiple imputation of missing data (in 17% subjects), VE estimated in the same intervals after vaccination were similar [56% (CI 33, 72%), 57% (CI 36, 71%), 25% (-10, 48%), 21% (-39, 55%)]. Conclusions: School-aged BCG vaccination offered moderate protection against tuberculosis for at least 20 years, which is longer than previously thought. This has implications for assessing the cost-effectiveness of BCG vaccination and when evaluating new TB vaccines.
|Number of pages||9|
|Journal||International Journal of Epidemiology|
|Publication status||Published - 1 Feb 2018|
Bibliographical noteFunding Information:
This work was supported by the National Institutes of Health Research Health technology Assessment (NIHR HTA) grant no 08/ 17/01. Other funding included a National Institute for Health Research (NIHR) Senior Investigator award NF-SI-0611–10168 (J.S.) NIHR Senior Investigator award NF-SI-0616–10037 (I.A.) and support from the MRC (I.A., L.R., P.M.), NIHR (I.A.,L.R.), BBSRC (P.M.) and PHE (I.A.).
© The Author 2017; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association.
- BCG vaccine
- Bacillus Calmette-Guerin
- Prevention and control