Tuberculin Response of Ethiopian Children After BCG Vaccination at Birth
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Date
1993-05
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Addis Abeba Universty
Abstract
In an attempt to evaluate the effectiveness of
neonatal BeG vaccination policy, a tuberculin survey was
conducted among different age groups of children in
Lideta awraja, Addis ababa who had received BeG
vaccination shortly after birth. The survey consisted of
assessing the immunization records and nutritional status
and conducting clinical histories and physical
examinations. Thereafter, each study subject's site of
BeG vaccination on the right shoulder was assessed and
the size of the scar graded. Tuberculin PPD tests were
also performed simultaneously, and
were read within 96-120 hours.
tuberculin reaction
A standard data
collection form was used to record address, age, sex,
body weight, BeG Scar and tuberculin response.
In addition, 60 children were revaccinated at the
age of 10 years (within the study period) and tuberculin
tests were performed 2 months after the second
vaccination.
Furthermore, 70 bacteriologically proven
tuberculosis patients were also tuberculin tested at the
beginning of the study, in order to check the potency of
tuberculin PPD test and to estimate the diagnostic value
of the test.
A total of 895 children were studied between October
1992 and February 1993. Of these 563 (63%) had a definite
BeG scar while the rest 331 (37%) were without a Scar.
The sex distribution in each group was similar. The
percentage of tuberculin non reactors in different age
groups was 39.5% at 2 months, 34.5% at 18 months, 39.1%
at 5-7 years, and 46% at 9-11 years. The number of
tuberculin non reactors initially showed a slight decline
from age 2 months and then an increase from age 18 months
onward; the overall pattern of induration si ze was
vi
statistically significant different between the age
groups (P< 0.001). Some 55% of the children without a
BeG scar showed no response to the tuberculin test, while
67% of those with a scar showed a positive tuberculin
response. A direct correlation was observed between
tuberculin reactivity and the size of BeG scar (P<O.OOl).
Meanwhile, a positive tuberculin reaction (>6 mm) was
observed in 11% of children despite the absence of the
BeG scar . Children without the BeG scar have 2.53 times
the risk of a negative tuberculin
those with a BeG scar (P<O. 001) .
reaction compared to
All the children
revaccinated at the age of 10 years showed a positive
tuberculin reaction and elicited a larger size of BeG
scar (> 4 mm). The tuberculosis patients showed
tuberculin reactions according to an unimodal
distribution. Of these 12% showed 10 -15mm induration.
A reaction of 10-15 mm were also observed in 3.3% of
children without a scar,ll% of children with a large scar
size( >5mm) and in 10% Of revaccinated children with out
tuberculosis infection. This revealed that the lack of
specificity of the test.
Overall, this finding emphasized the poor tuberculin
response in infants at the age of 2 months compared to 18
months after vaccination at birth and the waning effect
of tuberculin response at the age five years compared to
18 months. It indicates that the BeG induced allergy
tended to disappear in this age group and the need for
revaccination. Thus we suggest a further study in
deciding the age of first vaccination and revaccination
at the age of 5 years without tuberculin test.
In estimating coverage of vaccination, the presence
of BeG scar used as an indicator may overestimate by
almost a factor of two . Hence for accurate estimates we
recommend determining the rate of tuberculin reactors in
populations who have a BeG scar.
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Keywords
Tuberculin Response of Ethiopian Children After BCG Vaccination at Birth