title: BCG: the challenge continues.
abstract: It is widely recognized that BCG provides inconsistent and often inadequate protection against tuberculosis; however, simple estimates of efficacy fail to reflect the complexity of protection within, let alone between, populations. A decline in protection with an increase in age at vaccination has been seen in many studies. This may reflect 2 things: (i) that as people age they are exposed to a variety of mycobacterial challenges which may interfere with, or mask, the protection of BCG; and/or (ii) that the vaccine is better at protecting against primary disease than against either reactivation- or reinfection-type disease. These factors need to be taken into consideration when interpreting the results obtained with screening vaccines in animal models, as most of these models mimic acute primary-type disease. In addition, we have no evidence that the protection induced by BCG lasts for > 15 y, in any population. Recent data from South India indicate a complex interaction of age and time effects: BCG imparted consistent protection in children, but no protection for subjects > 15 y old, and may even have imparted negative protection among these older individuals. If true, these findings have important implications for efforts to develop a vaccine against adult pulmonary tuberculosis.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, UK.
authors.forename: P E
authors.initials: PE
authors.lastname: Fine
mesh_terms: D000328:Adult; D000367:Age Factors; D001500:BCG Vaccine / Q000008:administration & dosage*; D002648:Child; D006801:Humans; D007194:India; D013997:Time Factors; D014376:Tuberculosis / Q000517:prevention & control*; D014397:Tuberculosis, Pulmonary / Q000517:prevention & control; D014611:Vaccination
chemical_list: D001500:BCG Vaccine