BCG-induced increase in interferon-gamma response to mycobacterial antigens and efficacy of BCG vaccination in Malawi and the UK: two randomised controlled studies

• Published in: The Lancet (British edition) Vol. 20; pp. 1393 - 1401
• Main Authors: Black, G F, Weir, R E, Floyd, S, Bliss, L, Warndorff, D K, Crampin, A C, Ngwira, B, Sichali, L, Nazareth, B, Blackwell, J M, Branson, K, Chaguluka, S D, Donovan, L, Jarman, E, King, E, Fine, P E M, Dockrell, H M
• Format: Journal Article
• Language: English
• Published: 01.04.2002
• Subjects: Efficacy; Immune response; Malawi; Randomized controlled trials; Tuberculosis; Vaccines
• ISSN: 0140-6736

The efficacy of BCG vaccines against pulmonary tuberculosis varies between populations, showing no protection in Malawi but 50-80% protection in the UK. To investigate the mechanism underlying these differences, randomised controlled studies were set up to measure vaccine-induced immune responsiveness to mycobacterial antigens in both populations. The magnitude of the BCG-attributable increase in interferon-gamma responsiveness to M tuberculosis PPD, from before to one year post-vaccination, correlates better with the known levels of protection induced by immunisation with BCG than does the absolute value of the interferon-gamma or delayed type hypersensitivity response after vaccination. Suggests that differential sensitisation due to exposure to environmental mycobacteria is likely to be the most important determinant of the observed differences in protection by BCG between populations. (Original abstract - amended)