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BCG revaccination and tuberculin reactivity
N Kuyucu1, S Kuyucu, A Bakirtas
1Dr. Sami Ulus Children's Hospital, Telsizler, Ankara, Turkey. nkuyucu@yahoo.com
Insights
The number of BCG vaccines and scars impacts tuberculin reactivity in children. Indurations over 15 mm in high-prevalence areas warrant tuberculosis investigation, not just BCG assessment.
Area of Science:
- Pediatrics
- Immunology
- Infectious Diseases
Background:
- Tuberculin reaction interpretation in revaccinated children is debated.
- The influence of Bacillus Calmette-Guérin (BCG) vaccination schedules on tuberculin skin test (TST) reactivity requires clarification.
Purpose of the Study:
- To evaluate the effect of BCG vaccination number and scar concordance on tuberculin reactivity in children aged 7-14 years.
- To determine appropriate TST interpretation criteria in settings with high tuberculosis prevalence and routine BCG revaccination.
Main Methods:
- Purified protein derivative (PPD) testing was performed on 2810 healthy children.
- Children were stratified into four groups based on age (7-10 and 11-14 years) and concordance between vaccination records/scars.
- Tuberculin induration sizes were measured and analyzed in relation to vaccination history and time elapsed since the last dose.
Main Results:
- Mean induration sizes varied across groups, ranging from 8.0 mm to 10.9 mm.
- In groups with non-concordant vaccination/scar numbers, induration size decreased with increased time post-vaccination.
- In groups with concordant vaccination/scar numbers, induration size positively correlated with time post-vaccination.
Conclusions:
- BCG revaccination policies and time since vaccination influence TST results.
- An induration size of >= 15 mm should prompt further investigation for active tuberculosis in high-prevalence areas, rather than solely attributing it to BCG vaccination.
Abstract:
Interpretation of tuberculin reactions in revaccinated children is somewhat controversial among paediatricians. In this study, the effect of the number of BCG vaccines on tuberculin reactivity is evaluated. In 2810 healthy children aged 7 to 14 years with purified protein derivative (PPD) testing. Children were grouped according to the concordance of the number of the reported/documented vaccinations to the number of scars. Group 1 and 2 comprised of children 7 to 10 years of age and 11 to 14 years of age respectively, who had non-concordant scar numbers, and Group 3 and 4 included 7 to 10 and 11 to 14 years old children with concordant scar numbers. Mean tuberculin induration sizes were 8.0 +/- 5.7 mm for Group 1, 10.6 +/- 4.9 mm for Group 2, 9.8 +/- 4.9 mm for Group 3 and 10.9 +/- 4 mm for Group 4. As the time interval after the last dose of vaccination increased, mean induration sizes decreased in Group 1 and Group 3. In contrast, the mean reaction sizes of Group 2 and Group 4 showed a positive correlation with the period after the last dose of vaccine. It seems advisable that an induration size > or = 15 mm should not be attributed to BCG vaccination in countries with a high tuberculosis infection prevalence and routine BCG revaccination policies. A detailed investigation for tuberculosis infection and disease should be performed in those cases.