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.
Comments
RE: Flawed control
"Infants were randomized to receive 2-component diphtheria-tetanus-acellular pertussis vaccine; 5-component diphtheria-tetanus-acellular pertussis, diphtheria-tetanus-whole-cell pertussis; or diphtheria-tetanus (control group)"
The control group is useless in determining whether vaccines affect allergies since all 3 groups were given a vaccine. True control group would be unvaccinated
Vaccine safety: causal or coincidental associations
The story of a child who developed chronic arthritis following receipt of the varicella vaccine, while compelling, does not offer a formal proof of causality. At best, such an observation raises the hypothesis that vaccines may be a cause of immune-mediated disease. The only way to prove an association between receipt of a vaccine and the development of specific chronic diseases is by comparing the incidence of specific chronic diseases in vaccinated and unvaccinated groups. The hypothesis that vaccines might cause chronic allergic or autoimmune diseases has now been tested in many excellent, well-controlled studies. No evidence has been found to support the hypothesis. These clinical findings are consistent with important differences between immunologic events that occur after natural compared with those that occur after immunization.
A premise is mandatory: I strongly recommend all available immunizations in all infants and children; and the paper by Offit and Hackett on the concerns of parents about vaccinations is extremely convincing, but…
A brief report. AR was a healthy 18-month old girl with a family history completely negative for immunological diseases, except for an allergic rhinitis in the father. Growth and development were normal for age. She underwent all scheduled immunizations, without any side effect (DTaP, OPV, HBV, Hib, MMR) at the scheduled times. At the age of 18 months, she received varicella immunization. Two weeks later, a non-tender swelling of the left knee was noted. Because she was attending day care, an occult trauma while playing was thought to be involved. She did not refer pain, nor functional impairment was present. However, she was evaluated by a pediatric orthopedic and a pediatric radiologist, who made a diagnosis of “intra-articular effusion of unknown etiology”. No therapy was instituted. Eventually, an experienced pediatric rheumatologist saw the little girl and performed a needle aspiration of the joint effusion. A diagnosis of rheumatoid arthritis (pauciarticular, type 1) was made. As frequently seen in this disease, laboratory test resulted normal. The little girl was treated with intra-articular corticosteroids and, by 6 months, the effusion was resolved. She is currently doing well, and ophthalmological and rheumatologic follow-up are negative. Based on clinical and laboratory grounds, the rheumatologist firmly denied the possibility that the condition was a “reactive arthritis”, as those seen following natural varicella infection. Currently, the most important known risk factor for this baby is that she the relative of a doctor: actually, she is my beloved daughter.
Despite this, I still strongly recommend the varicella immunization…
Luca Rosti