Atopic disorders among Estonian schoolchildren in relation to tuberculin reactivity and the age at BCG vaccination

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Abstract
Published data about a relationship of atopic diseases to Bacillus Calmette-Guérin (BCG) vaccination and tuberculin responses are inconsistent. Our aim was to determine this association in a country with a low prevalence of allergies. A random sample of 10-11-year-old schoolchildren in Tallinn was studied by a parental questionnaire (n = 979) and skin-prick tests (n = 643), according to the International Study of Asthma and Allergies in Childhood. Data about BCG vaccinations and tuberculin tests were obtained from school records (n = 723). The prevalence of allergic symptoms and atopy was similar in children vaccinated during the first month of life and later. Positive tuberculin responses (> or =5 mm) were inversely related to symptoms of asthma [odds ratio (OR) 0.10 (95% confidence interval 0.00-0.68) for exercise-induced wheezing; OR 0.37 (0.12-0.99) for night cough], and eczema [OR 0.53 (0.28-0.98)] but not to atopy. However, among BCG-revaccinated children, atopy tended to be more common in tuberculin responders, and the atopic children were significantly more likely to have a positive tuberculin response after the revaccination than would be predicted by their first test. We found no protective effect of early BCG vaccination against atopy in school age, although tuberculin responses and allergic symptoms were inversely related.