Children who receive routine childhood immunizations are not more likely to develop allergies later in life, despite contrary claims from parents, and are even protected against allergic disease, a cohort study indicates.
"What we hear from parents is that vaccination leads to more allergic reactions in later life," said Olf Herbarth, MD, from the University of Leipzig in Germany.
The study, which compared vaccinated with unvaccinated children, showed "a lower prevalence of allergic disorders if children had been vaccinated, even in children predisposed to allergies, so a higher risk of allergies is not a consequence of vaccination," he told Medscape Medical News.
Results were presented at the World Allergy Organization International Scientific Conference and Congress of the Brazilian Association of Allergy and Immunology in Rio de Janeiro.
Dr. Herbarth and colleagues looked at three separate birth cohorts, involving 2187 children 5 and 6 years of age. The first cohort came from a cross-sectional study of children born in 1988 and 1989, the second came from a multicenter birth study of children born in 1994 and 1995, and the third came from a study of children at increased risk for atopic disease because of parental history of atopy.
Researchers determined vaccination history with questionnaires, vaccination certifications, and vaccination titers. All vaccinations recommended by the German Standing Committee on Vaccination were considered.
Outcomes included the development of atopic eczema and any other symptoms of allergic disease.
In all three cohorts, the lower the vaccination rate, the higher the prevalence of allergic disease. In the pooled dataset, atopic eczema was more common in children who had not been vaccinated than in those who had (29.6% vs 22.1%).
Similarly, symptoms of other allergic diseases were more common in children who had not been vaccinated than in those who had (38.9% vs 32.7%)
Even in the birth cohort identified as being at high risk for atopic disease because of a parental history and high cord blood levels of IgE (>0.9 kU/L), vaccination was associated with a 26% lower risk for any allergic symptoms (odds ratio [OR], 0.74) and a 34% lower risk for eczema (OR, 0.66) after adjustment for all possible confounders, including cats, smoking during pregnancy, and history of renovation in the home.
An analysis limited to the presence of allergic disease and vaccination titers showed a significant 31% reduction in both eczema and allergic symptoms in vaccinated children (P = .002).
"The question we had was whether parental predisposition to allergic disease dominates the allergic profile," Dr. Herbarth explained. "We found that parental predisposition was stronger than other influences, so even children predisposed to develop allergies are protected against allergies through vaccination."
The linking of vaccination to allergies by parents has been going on for years, said Paul Offit, MD, from the Children's Hospital of Philadelphia. That thinking is likely related to the "hygiene hypothesis," he explained.
"If you look at children in the developing world — where they are much more likely to be exposed to infections earlier in life and where their intestines are often colonized by toxin-producing bacteria and parasites — the incidence of allergies and asthma is lower than in children in the developed world," he told Medscape Medical News.
This is what prompted the formulation of the hygiene hypothesis, which, in Dr. Offit's view, is not a hypothesis but a fact.
"I think the hygiene hypothesis is where this all comes from, but I think it has nothing to do with vaccines," he said. "All of the diseases that vaccines prevent have nothing to do with the level of sanitation in a country or hygiene in the home. You are not targeting agents with vaccines that are more prone to occur in one country or another."
In addition, the diseases that childhood vaccines prevent in the first years of life are but a small proportion of the diseases children are going to be exposed to over a lifetime, Dr. Offit explained. Not having children vaccinated still leaves them vulnerable to many other diseases that are not vaccine-preventable, he added.
Dr. Herbarth and Dr. Offit have disclosed no relevant financial relationships.
World Allergy Organization International Scientific Conference (WISC) and Congress of the Brazilian Association of Allergy and Immunology. Abstract 1014. Presented December 7, 2014.
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Cite this: Vaccination Protects Children Against Allergic Disease - Medscape - Dec 11, 2014.