Effects of childhood infections and vaccination on development of atopy

Sir,

Are infections in infancy protection factors against atopy? Is childhood vaccination a risk factor for the development of atopy?

Aiming to provide for consideration of the homeopathic community scientific answers for the important questions above, I presented a systematic review of all Medline (1993–2004) papers which could provide direct epidemiological evidence on the subject. The conclusion of this review was a double negative answer, i e:

• infections in infancy are not protection factors against atopy,

• vaccination is not a risk factor for the development of atopy.[ ¹ ]

These results engendered some debate not only in past issues of Homeopathy, but also at the 60th Congress of the Liga Medicorum Homeopathica Internationalis, Berlin, where this review was presented in the form of a lecture. Unprejudiced debate about childhood infections and their vaccines seems an important step for a Homeopathy accustomed to act in accordance to observations ‘empirically cited over the centuries by homeopathic physicians’.[ ² ]

Childhood infections have been hypothesized as protective against allergy by indirect clues. For instance, there are consistent associations between allergic manifestations and urban, smaller and wealthier families.[ ³ ] If that hypothesis proved to be true, vaccination—avoiding childhood infections might be allergenic. However, studies in humans populations on the direct effect of infections or vaccines on atopy development have pointed to the opposite conclusion, i e, in the light of present knowledge, childhood infections promote atopy and most of the common vaccines are neutral or even protective against atopy.[ ^3–7 ]

There are probably still unclear anti-allergic factors that were initially miscomprehended as infectious diseases in early infancy. For instance, in the debate featured in the October 2005 issue of Homeopathy, concerning the results of the review by Flohr et al, Teixeira mentioned that the ‘results showed that there was prospective evidence to support an inverse relationship between atopic dermatitis and endotoxins, early day care and animal exposure’.[ ⁸ ] Unfortunately, Teixeira did not mention that, according to the conclusion of Flohr et al, that relationship is not due to any childhood infection, like measles or pertussis: ‘Although population-based studies have suggested a consistent inverse relationship between atopic dermatitis and increasing family size, this does not seem to be explained by a straightforward increased exposure to a single environmental pathogen. The effect seen with early day care, endotoxin, and animal exposure may be due to a nonpathogenic microbial stimulus of a chronic or recurrent nature.’[ ⁹ ] Acute childhood infectious diseases cannot be classified as ‘nonpathogenic microbial stimulus of a chronic or recurrent nature’. Helminths or intestinal flora could be responsible for this chronic stimulus and protection against atopic dermatitis, as stressed by my review and many studies since the 1970s.[ ¹⁰ ]

Teixeira also quoted one of the conclusions of Koppen et al in their review on vaccination and atopy: ‘at this moment there is insufficient evidence to accept or reject a causal relation between early BCG vaccination and the development of allergic diseases’.[ ⁸ ] However, he did not quote the final conclusions of the article: ‘Based on the best available epidemiological evidence, however, we conclude that there is no convincing evidence that these immunological mechanisms translate into a contribution of infant vaccinations against diphtheria, pertussis, tetanus, mumps and rubella to the development of atopic diseases. Therefore, our review of current evidence strengthens earlier conclusions that these infant vaccinations do not increase their risk of development of allergic diseases.[ ¹¹ ]

Eskinazi proposes a workshop to further discuss vaccination and atopy.[ ¹² ] His standpoint: ‘the real issue is not whether vaccines are good or bad in general’ agrees with mine: ‘Vaccines are heterogeneous products, each one with their specific immunogenic characteristics, which should be separately analyzed’.[ ¹ ] In spite of that, up to the present, ‘the best available epidemiological evidence’ shows us that childhood infections—and not common vaccines—are to be feared in regard to atopy sensitization or disease. Until new epidemiological data contest these findings, I see no reason for a workshop, unless we decided to discuss why Homeopathy has not taken in consideration Hahnemann′s observations, he emphasized the benefits of Jenner's vaccination[ ¹³ ] and the risk that epidemics represented for the development of chronic diseases.[ ¹⁴ ]

• References

• 1 Adler U.C. The influence of childhood infections and vaccination on the development of atopy: a systematic review of the direct epidemiological evidence. Homeopathy 2005; 94 (03) 182-195.
• 2 Teixeira M.Z. Is there scientific evidence that suppression of acute diseases in childhood induces chronic diseases in the future?. Homeopathy 2002; 91: 207-216.
• 3 Prescott S.L. Allergy: the price we pay for cleaner living?. Ann Allergy Asthma Immunol 2003; 90 (03) 64-70.
• 4 Kemp A., Björkstén B. Immune deviation and the hygiene hypothesis: a review of the epidemiological evidence. Pediatr Allergy Immunol 2003; 14 (02) 74-80.
• 5 Karmaus W., Botezan C. Does a higher number of siblings protect against the development of allergy and asthma? A review. J Epidemiol Community Health 2002; 56 (03) 209-217.
• 6 Koppen S., de Groot R., Neijens H.J., Nagelkerke N., van Eden W., Rümke H.C. No epidemiological evidence for infant vaccinations to cause allergic disease. Vaccine 2004; 22 (25/26) 3375-3385.
• 7 Rottem M., Shoenfeld Y. Vaccination and allergy. Curr Opin Otolaryngol Head Neck Surg 2004; 12 (03) 223-231.
• 8 Teixeira M.Z. The hygiene hypothesis revisited. Homeopathy 2005; 94 (04) 248-251.
• 9 Flohr C., Pascoe D., Williams H.C. Atopic dermatitis and ‘hygiene hypothesis’: too clean to be true?. Br J Dermatol 2005; 152: 202-216.
• 10 Kim S.D., Drake-Lee A.B. Infection, allergy and the hygiene hypothesis: historical perspective. J Laringol Otol 2003; 117 (12) 946-950.
• 11 Koppen S., de Groot R., Neijens H.J., Nagelkerke N., van Eden W., Rümke H.C. No epidemiological evidence for infant vaccinations to cause allergic disease. Vaccine 2004; 22: 3375-3385.
• 12 Eskinazi D. Vaccinations: for or against. Homeopathy 2005; 94 (04) 252-253.
• 13 Hahnemann S. Organon der Heilkunst: aude sapere. 6th edn. Richard Haehl, Leipzig, Schwuabe, 1921, Heidelberg, Haug, 1988, paragraph 46.
• 14 Hahnemann S. Die chronischen Krankheiten, ihre eigentüml. Natur u. homöopath. Heilung. Vol 1, 2nd edn. 1835. Heidelberg, Haug, 4th print, 1988, p166.