Assessing the effect of foreign travel and protection by BCG vaccination on the spread of tuberculosis in a low incidence country, United Kingdom, October 2008 to December 2009

The contribution of travel to high incidence countries and the impact of the discontinuation of universal Bacillus Calmette-Guérin (BCG) vaccination to the recent rise in tuberculosis (TB) in the United Kingdom remain unclear. An outbreak in a college presented an opportunity to assess these. A cohort of students answered a questionnaire assessing risk factors for TB. Participants were screened with an interferon gamma release assay (IGRA). Unadjusted and adjusted odds ratios (OR) were calculated using logistic regression. Among 2,284 students, 400 (17.5%) were diagnosed with TB infection. A higher risk was noted for travel to a high incidence area in the past two years (OR: 1.39; 95% confidence interval (CI): 1.04-1.89) and among those with the greatest exposure to the index case (OR: 3.94; 95% CI: 2.60-5.97). There was no association between BCG and risk of infection (OR: 1.05; 95% CI: 0.80-1.39). The lack of a protective effect by BCG on TB infection supports the discontinuation of universal vaccination. The association with foreign travel suggests the need to assess the cost-effectiveness of serial IGRA testing and treatment of positive persons among returning travellers.