Koppen S, de Groot R, Neijens HJ, et al. Vaccine. 2004;22:3375–3385
Purpose of the Study.
Because the prevalence of allergic disease has increased in the last decades and one theory for the increase is immune dysregulation associated with hygiene and reduced infection, the study sought to determine if healthy children vaccinated at an early age have an increased risk for the development of allergic disease.
Epidemiologic studies with original data on the correlation between vaccination with diphtheria, pertussis, tetanus (DPT), measles, mumps, rubella (MMR), and bacille Calmette-Guérin (BCG) immunizations in infancy and the development of allergic diseases were selected and reviewed for their quality and validity. To increase the likelihood of considering all relevant literature, Medline searches (from January 1966 to March 2003) were performed, bibliographic lists from retrieved articles were reviewed, and experts in the field were asked to identify relevant articles.
Methodologic design and quality varied markedly between the studies reviewed. Ethical issues regarding vaccination precluded randomized, controlled trials (only 1 such study was found). Many studies did not address possible confounders such as the presence of lifestyle factors, which resulted in bias. The studies offering the stronger evidence indicate that the investigated infant vaccinations do not increase the risk of developing allergic disease. Furthermore, BCG does not seem to reduce the risk of allergies.
The authors concluded that the reviewed epidemiologic evidence indicates that current infant vaccines do not cause allergic diseases.
In an effort to reduce the risk of development of allergies, families knowledgeable about the “hygiene hypothesis” sometimes worry that vaccination of their children will increase the risk of allergic disease. Although most pediatricians can easily point out that vaccination carries clear advantages for their use and that a concern for allergy would not be a good reason to defer immunization, this analysis of available data additionally supports the argument that there is no evidence to indicate that childhood vaccinations are the cause of the increase in allergic disease in Westernized countries. There is likely a complex interplay of environmental factors contributing to the apparent skewing toward an allergic, or T-helper 2–dominant, immune response and the resulting increased prevalence of atopic disease.