The medical establishment has been at pains lately to quell public fears about vaccinations. These fears have largely been aroused by researchers in the US, who have suggested that immunisation may induce diabetes in susceptible individuals (Infect Dis Clin Pract, 1997; 6: 449-54).
Keen to calm the concerns of the public which have been stirred up by excited media coverage several organisations, including the World Health Organisation, National Institute for Allergy and Infectious Disease and the Centre for Disease Control, reviewed the data from this controversial US study at a two day conference. The claims of the paper were rejected, and further research is ongoing.
Research examining the pros and cons of vaccination is plentiful and well documented, but has tended to focus on the short term effects. Recently, however, several papers have expressed a concern about the possible association between immunisation and the onset of long term chronic conditions, in particular, allergic diseases. Kemp et al (Epidemiology, 1997; 8: 678-80) presented data consistent with the hypothesis that some component of infant immunisation may increase the risk developing asthma in childhood.
Other allergic illnesses such as eczema, hay fever, Crohn's disease and IBS (Lancet, 1995; 345: 1071-4) have also been linked with immunisation, and there is growing concern about a possible relationship between vaccination and autoimmune diseases such as diabetes and rheumatoid arthritis.
The public may have good cause for concern. Immunisation is one of the most widely used methods of disease prevention. In 1990, it is estimated that approximately 1479 million immunisations were administered globally.
There is no doubt that allergic and autoimmune diseases are on the rise in the developed world. Thirty years ago, asthma was considered rare; today it affects 20-30 per cent of the population in Britain and the US, and kills 5000 people each year in the US alone. Studies in Britain have indicated an increase from 5 to 16 per cent in the incidence of childhood eczema, and an increase in hay fever from 9 to 15 percent (Clin Experi Allergy, 1993; 23, 484-92).
Doctors are reporting an increase in the number of children who develop insulin dependent (type-1) diabetes at a younger age.
The diseases recently linked to immunisation all have one thing in common: they are thought to stem from a misguided immune system response to a trigger. But beyond this, there is no straight forward cause and effect relationship, since factors triggering the response can be varied and complex. So far, the medical establishment seems reluctant to accept the suggestion that immunisation may be one of the triggers leading to a malfunction in the immune system, even though a strong theoretical link already exists.
Immune system function is controlled by what are known as Th1 and Th2 cells. When functioning correctly, Th1 cells send out messages instructing cells infected by a virus or bacteria to kill the infectious agent.
Th2 cells are responsible (among other things) for preventing parasites from entering the gut wall, which they do through the production of immunoglobulinE (IgE), histamines and mucus. Both Th1 and Th2 cells can be stimulated by allergens, but it is the Th2 cells which are responsible for the usual allergic response of tissue inflammation and excessive mucus production.
In order for the immune system to function properly, a balance between Th1 and Th2 cells must be made, as Th1 cells are needed to inhibit the action of Th2 cells.
However, all vaccines with the exception of the tuberculosis (BCG) jab stimulate only the part of the immune system responsible for the production of Th2 cells. So, it is theoretically possible that immunisation may contribute to the development of allergic disease by causing an imbalance in this ratio.
Several studies have found that vaccines produce a greater IgE response (Ped Allergy Immunol, 1994; 5: 118-23; Vaccine, 1995; 13: 669-73). One animal study showed that histamine release, which occurs during an allergic response, was enhanced by vaccination (Eur J Pharmacol, 1980; 62: 261-8).
Such relationships between vaccinations and subsequent ill effects raise complex issues, and more long term research is clearly needed, though in some quarters even the suggestion of research seems to meet with opposition.
An editorial in the British Medical Journal in July last year (317: 159-60) raised questions about the ethics of leaving a control group unvaccinated for the duration of the research. Such questions have not been asked with regard to the effects of vaccinating infants, knowing that such actions may be contributing to the onset of long term, chronic diseases.