Addressing Parents’ Concerns: Do Vaccines Cause Allergic or Autoimmune Diseases?


Paul A. Offit and Charles J. Hackett

Excerpt:

Abstract

Anecdotal case reports and uncontrolled observational studies in the medical literature claim that vaccines cause chronic diseases such as asthma, multiple sclerosis, chronic arthritis, and diabetes. Several biological mechanisms have been proposed to explain how vaccines might cause allergic or autoimmune diseases. For example, allergic diseases might be caused by prevention of early childhood infections (the “hygiene hypothesis”), causing a prolongation of immunoglobulin E-promoting T-helper cell type 2-type responses. However, vaccines do not prevent most common childhood infections, and large well-controlled epidemiologic studies do not support the hypothesis that vaccines cause allergies. Autoimmune diseases might occur after immunization because proteins on microbial pathogens are similar to human proteins (“molecular mimicry”) and could induce immune responses that damage human cells. However, wild-type viruses and bacteria are much better adapted to growth in humans than vaccines and much more likely to stimulate potentially damaging self-reactive lymphocytes. Consistent with critical differences between natural infection and immunization, well-controlled epidemiologic studies do not support the hypothesis that vaccines cause autoimmunity.
Flaws in proposed biological mechanisms that explain how vaccines might cause chronic diseases are consistent with the findings of many well-controlled large epidemiologic studies that fail to show a causal relationship. 
Anecdotal reports and uncontrolled observational studies in the medical literature118 and stories in the news media and on the Internet allege that vaccines cause chronic diseases such as multiple sclerosis, diabetes, chronic arthritis, hay fever, and asthma. Because of these reports, some parents have chosen to delay or withhold vaccines for their children. In response to concerns by parents and health care professionals, the Institute of Medicine recently reviewed studies examining the relationship between multiple immunizations and immunologic dysfunction.19
We will discuss the pathogenesis of allergies, multiple sclerosis, type 1 diabetes, and chronic arthritis and the plausibility of biological mechanisms that explain how vaccines might cause these diseases. In addition, we will review well-controlled epidemiologic studies that investigate the relationship between vaccines and chronic diseases.





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