BCG vaccination reduces risk of infection with Mycobacterium tuberculosis as detected by gamma interferon release assay.
OBJECTIVE
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).


CONCLUSIONS
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.
Eisenhut
Michael
M
Luton and Dunstable Hospitals NHS Foundation Trust, Luton LU4 0DZ, United Kingdom. michael_eisenhut@yahoo.com
Paranjothy
Shantini
S
Abubakar
Ibrahim
I
Bracebridge
Sam
S
Lilley
Mike
M
Mulla
Rohinton
R
Lack
Kay
K
Chalkley
Denise
D
McEvoy
Marian
M
D001500:BCG Vaccine / Q000008:administration & dosage*; D002648:Child; D004196:Disease Outbreaks / Q000517:prevention & control*; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D012307:Risk Factors; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000276:immunology / Q000517:prevention & control*
D001500:BCG Vaccine; D007371:Interferon-gamma