Protective effect of BCG vaccination in a nursery outbreak in 2009: time to reconsider the vaccination threshold?

Background: In July 2008 a case of smear-positive pulmonary tuberculosis (TB) in a white UK-born nursery teacher was notified in London. The case had been symptomatic for 9 months while working in the nursery. The outbreak is described and the protective effect of BCG vaccination against latent Mycobacterium tuberculosis infection as measured by an interferon gamma release assay (IGRA) is assessed.