Tuberculin Response of Ethiopian Children after Big Vaccination at Birth
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Date
1993-05
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Addis Ababa University
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 tuberculin reaction ___ _
were read within 96- 120 hours. 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 bacter iologically 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 va lue
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 in durationstatistically significant different between the age
groups (P< 0.001). Some 55% of the children without a
BCG 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 BCG scar (P<O.OOl) .
Meanwhile, a positive tuberculin reaction (>6 mm) was
observed in 11% of c hildren despite the absence of the
BCG scar. Children without the BCG scar have 2.53 times
the risk of a negative tuberculin
those with a BCG scar (P<O. OOl) .
reaction compared to
All the children
revaccinated at the age of 10 years showed a positive
EUJ5erculin reac1:1on and---eric il:ed a larger size of-S-CG
scar (> 4 rom) . The tuberculosis patients showed
tuberculin reactions according to an unimodal
distributi on. Of these 12% showed 10 -15rom induration.
A reaction of 10- 15 rom were also observed in 3.3% of
children without a scar,ll% of children with a large scar
size( >5rom) 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 BCG induced a llergy
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 vacc ination, the presence
of BCG 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 BCG s car. size was In assessing the diagnostic value of tuberculin PPD
test, it was found less specific to determine the problem
of tuberculosis in the community at a cut-off point of
10mm. Therefore for a better estimate, a cut- off point
of 15mm and above should be considered.
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Keywords
Tuberculin Response of Ethiopian Children