Smallpox vaccination and risk of allergy and asthma

Background: It has been proposed that childhood vaccinations may influence the development of allergy. Atopy and allergic diseases have increased after routine smallpox vaccination was stopped in the 1970s. Objective: we examined whether administration of smallpox vaccination during childhood was associated with a decreased risk of atopy, allergic rhinitis, and asthma. Methods: The occurrence of atopy, allergic rhinitis, and asthma was studied in nearly 2000 women participating in a national birth cohort study. Detailed information on smallpox vaccination was available from school health records. Atopic status was assessed serologically by a specific response to 11 common inhalant allergens by using serum samples obtained from the women during the period 1997 to 2001. Information on allergic rhinitis and asthma was available from telephone interviews. Results: we found no association between having been vaccinated against smallpox in childhood and risk of atopy or allergic rhinitis. Smallpox vaccination was associated with a slightly decreased risk of asthma. There was no association between age at smallpox vaccination and risk of atopy, allergic rhinitis, or asthma. Adjusting for birth cohort, sibship size, age of the woman's mother at birth, and social class in childhood did not change these results. Conclusion: Our findings do not suggest that childhood vaccination against smallpox, even if given early in life, influences the development of atopy or allergic rhinitis. The association with asthma should be interpreted with caution and needs further study.