Sir--In
his Oct 21 commentary,1 Roni Grad calls for more research into the
substantial increase in the prevalence of asthma over the past 30 years.
Atopic disorders such as allergic rhinitis, eczema, and asthma, as well as malignant
diseases are characterised by a predominant T-helper-2 (Th2) immune response. Better
housing and hygiene, the decline in infectious diseases, and current immunisation regimens
might have contributed to the increase in these diseases.2 There is, however,
also an increase in T-helper-1 (Th1)-mediated autoimmune diseases such as
insulin-dependent diabetes mellitus. But, of the environmental factors, early childhood
vaccinations might be the important contributing factor, leading to an increase in these
diseases of disordered immune regulation.
Thomas Ball and colleagues3 have shown that childhood infections, especially
in the first 6 months of life, seem to prevent asthma later in life. Cells infected with a
virus or intracellular parasites and tumour cells are destroyed by a Th1 response.
Non-replicating vaccines do not, however, cause a vigorous Th1 response because they do
not stimulate antigen presenting cells sufficiently in the maturing immune system of the
neonate.4 Early childhood vaccines could, therefore, cause a disturbance in the
immune regulation of the maturing immune system, priming it to react in a certain way.
Such an effect could explain the results of the International Study of Allergies and
Asthma in Childhood study,5 which shows that the prevalence of asthma, atopic
eczema, and allergic rhinoconjunctivitis is most consistently high in the UK, Ireland,
Australia, USA, and New Zealand. These countries have long established vaccination
programmes. Other obser-vations show that, although foodborne and orofecal microbes are
thought to protect against atopy, the prevalence of atopic diseases has increased in poor
African cities, where hygiene has not had the same effect on these microbes as in the
affluent countries. The imple-mentation of immunisation pro-grammes in these areas could
explain this rising trend.
As a family physician I am becoming increasingly uncomfortable with the diseases to
which vaccines might contribute later in life. I suggest the need for epidemiologial
studies to assess whether the currently perceived benefits still outweigh the long-term
dis-advantages. Consideration should be given as to whether vaccination should be
postponed until after the first 6 months of life. Especially in view of the increasing
number of childhood vaccines, should we investigate with some urgency whether they are
becoming too much of a good thing?
Wouter Havinga
St Luke's Medical Centre, Stroud, Glos GL5 4EX, UK (e-mail:havinga@globalnet.co.uk)
1 Grad R. Risk of asthma in children with exposure to mite and cat allergens. Lancet
2000; 356: 1369-70. [Text]
2 O'Byrne KJ, Dalgleish AG, Browning M, Steward WP, Harris AL. The relationship between
angiogenesis and the immune response in carcinogenesis and progression of malignant
disease. Eur J Cancer 2000; 36: 151-69. [PubMed]
3 Ball TM, Castro-Rodiriguez JA, Griffith KA, Holberg CJ, Martinez FD, Wright AL.
Siblings, day-care attendance, and the risk of asthma and wheezing during childhood.
N Engl J Med 2000; 343: 538-43. [PubMed]
4 Atkins B. T-cell function in newborn mice and humans. Immunol Today 1999; 20: 330-35. [PubMed]
5 The International Study of Asthma and Allergies in Childhood (ISAAC) Steering
Committee. Worldwide variation in prevalence of symptoms of asthma, allergic
rhinoconjunctivitis and atopic eczema: ISAAC. Lancet 1998; 351: 1225-32. [Text]
