BCG vaccination reduces risk of infection with Myobacterium tuberculosis as detected by gamma interferon release assay

Michael Eisenhut, Shantini Paranjothy, Ibrahim Abubakar, Sam Bracebridge, Mike Lilley, Rohinton Mulla, Kay Lack, Denise Chalkley, Marian McEvoy

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AIMS: To investigate whether BCG vaccination, in addition to a reduction of active tuberculosis, leads to a reduction of Mycobacterium tuberculosis infection during an outbreak of tuberculosis. METHODS: Pupils (n=199) of a Junior School exposed to a pupil with active pulmonary tuberculosis were screened using a gamma interferon release assay for detection of M. tuberculosis infection (ex vivo ELISPOT assay). Relative risk of M. tuberculosis infection and pulmonary tuberculosis associated with BCG vaccination were calculated and adjusted for exposure risk. RESULTS: Twenty-nine percent of children with previous BCG vaccination had a reactive gamma interferon release assay compared with 47% of unvaccinated children (unadjusted RR 0.61, 95%CI 0.39, 0.96). The protective effect of BCG vaccination persisted following adjustment for other risk factors for infection like ethnicity and proximity to the source case reflected in membership of class and activity groups (corrected relative risk 0.26, 95%CI 0.09, 0.69 and risk reduction of 74%, 95%CI 31%, 91%). A higher proportion of unvaccinated children (11%) were diagnosed with active pulmonary tuberculosis compared with 5% of vaccinated children (RR 0.51 95%CI 0.15, 1.70). CONCLUSION: BCG vaccination was associated with a reduction of M. tuberculosis infection diagnosed by gamma interferon release assay testing in school children during a point source outbreak.
Original languageEnglish
Pages (from-to)6116-6120
Number of pages5
Issue number44
Publication statusPublished - 19 Oct 2009

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