Evidence of protection from childhood BCG against tuberculosis (TB) in adulthood, when most transmission occurs, is important for TB control and resource allocation.
We conducted a population-based case-control study of protection by BCG given to children aged 12 to 13 years against tuberculosis occurring 10 to 29 years later. We recruited UK-born white subjects with tuberculosis and randomly sampled white community controls. Hazard ratios and 95% confidence intervals were estimated using case-cohort Cox regression, adjusting for potential confounding factors, including socio-economic status, smoking, drug use, prison and homelessness. Vaccine effectiveness (VE=1-hazard ratio) was assessed at successive intervals more than 10 years following vaccination
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, 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%).
School-age BCG vaccination offered moderate protection against tuberculosis for at least 20 years which is longer than previously thought. This has implications for assessing the costeffectiveness of BCG vaccination and when evaluating new TB vaccines.
- BCG Vaccine
- Bacillus Calmette-Guerin
- prevention and control