Mycobacterium tuberculosis infection in First Nations preschool children in Alberta: implications for BCG (bacille Calmette-Guérin) vaccine withdrawal.
BACKGROUND
On April 1, 2004, BCG (bacille Calmette-Guérin), a tuberculosis (TB) control vaccine, was discontinued in all but four high-risk communities in Alberta. To confirm the safety of vaccine withdrawal, and for future planning, the annual risk of infection (ARI) was determined in preschool First Nations children.


METHODS
First Nations children born into reserve communities in Alberta between April 1, 1998 and March 31, 2004, and still living on reserve in 2004-2005, were identified. Health centre TB histories were validated by cross-referencing the birth cohort with the provincial TB Registry. Children that were not BCG vaccinated and not known to be tuberculin skin test (TST) positive underwent a TST. Birth cohort children were grouped as follows: (i) BCG vaccinated; (ii) BCG non-vaccinated, no TST; (iii) BCG non-vaccinated, TST; (iv) BCG vaccination status unknown. The ARI was calculated and the age and community characteristics of the groups were compared.


RESULTS
There were 8447 children in the 6-year birth cohort, 4699 (55.6%) vaccinated, 2696 (31.9%) non-vaccinated, and 1052 (12.5%) whose vaccination status was unknown. Of the non-vaccinated children, 1921 (71.3%) were tested and only 2 were TST positive. No other TST positive, BCG non-vaccinated children were identified in the TB Registry cross-match. The prevalence of infection in 2004-2005 was 0.1% and the ARI was 0.03%. The community risk of TB exposure was comparable in tuberculin-tested and non-tested BCG non-vaccinated children.


CONCLUSIONS
In low BCG-uptake First Nations communities in Alberta, the ARI is low and it is safe to withdraw BCG.
Jacobs
Sandy
S
First Nations and Inuit Health Branch, Alberta Region.
Warman
Andrea
A
Roehrig
Natalie
N
Yacoub
Wadieh
W
Wijayasinghe
Chandrani
C
Richardson
Ruth
R
Benjamin
Elaine
E
Chong
Huey
H
Manfreda
Jure
J
Long
Richard
R
D000416:Alberta / Q000453:epidemiology; D001500:BCG Vaccine / Q000600:supply & distribution*; D002675:Child, Preschool; D005260:Female; D006303:Health Services, Indigenous; D006801:Humans; D015994:Incidence; D007198:Indians, North American / Q000706:statistics & numerical data*; D008297:Male; D009164:Mycobacterium Infections / Q000453:epidemiology* / Q000517:prevention & control; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D015995:Prevalence; D018570:Risk Assessment; D014374:Tuberculin Test
D001500:BCG Vaccine