Sir--In their Seminar, A E Tattersfield and colleagues (Oct 26, p 1313)¹ refer to the factors that can cause the immune system of children to polarise towards a Th2 rather than a Th1 lymphocyte phenotype. However, they do not mention any study exploring the incidence of childhood asthma in relation to immunisation protocols. BCG and other mycobacteria vaccines tend to facilitate this shift towards the Th1 phenotype, whereas most other commonly used vaccines tend to have the opposite effect.

We investigated the possible link between early vaccinations and asthma in two homogeneous populations of children. In the first group (n=446), all children (mean age 8 years) had been breastfed for more than a year and had received only breastmilk during the first 6 months.² In the second group, all 274 children were pupils of British Rudolf Steiner schools, and shared the same anthroposophic lifestyle. In both groups we found a significant correlation between pertussis vaccination and asthma.

However, we could not find the same correlation among the 210 pupils of a French Rudolf Steiner school that did not follow the same immunisation programme as the British one. Most French pupils who had received pertussis vaccination (and the vaccinations usually associated with pertussis) had previously received BCG. We postulated that diphtheria-tetanus-pertussis vaccination is a risk factor for asthma if it is not preceded by BCG.³ By combining the data from these three groups, we identified 214 children who had no vaccination at all: four were diagnosed as having asthma.

We conclude that, in the future, epidemiological studies of asthma should look at the immunisation status of the population under study.

*Michel Odent, Esther Culpin

Primal Health Research Centre, 72 Savernake Road, London NW3 2JR, UK (e-mail:modent@aol.com)

1 Tattersfield AE, Knox AJ, Britton JR, Hall IP. Asthma.  Lancet 2002; 360: 1313-22. [Text]

2 Odent M, Culpin EE, Kimmel T. Pertussis vaccination and asthma: is there a link?  JAMA 1994; 272: 592-93. [PubMed]

3 Odent M. Future of BCG.  Lancet 1999; 354: 2170-70. [Text]