Age at bacille Calmette-Guérin vaccination and risk of allergy and asthma

Background: It has been proposed that early age at bacille Calmette-Guérin (BCG) vaccination protects against the development of allergy. Objective: To study whether early age at BCG vaccination was associated with a decreased risk of atopy, allergic rhinitis, and asthma compared to BCG vaccination at later ages in childhood. Methods: The occurrence of atopy, allergic rhinitis, and asthma was studied in nearly 2000 women participating in the Danish National Birth Cohort study. Detailed information on age at BCG vaccination (age 0-15 years) was available from school health records. Atopic status was assessed serologically by a specific response to 11 common inhalant allergens using serum samples obtained from the women during the period 1997-2001. Information on allergic rhinitis and asthma was available from telephone interviews. Results: Approximately 85% of the women had been BCG-vaccinated. Age at BCG vaccination was not associated with risk of atopy, allergic rhinitis, or asthma. The odds ratio of atopy, allergic rhinitis, and asthma associated with being vaccinated during the first year of life was 1.05 (95% CI 0.71-1.56), 1.42 (95% CI 0.85-2.36), and 1.71 (95% CI 0.91-3.20), respectively, compared with being vaccinated at the age of 7 years. Adjustment for birth cohort, sibship size, age of the woman's mother at birth, and social class in childhood did not affect the results. Conclusion: Our findings suggest that age at BCG vaccination in childhood does not influence the development of allergy or asthma.