A number of excipients are used in the production of vaccines. These include:
Thimerosal (thiomersal in Europe), a mercury derivative used as a preservative, is a common cause of allergic or sensitivity reactions (Contact Dermat, 1989; 20: 173-6). Animal studies have also shown that mercury can cause immune suppression (Toxicol Appl Pharmacol, 1983; 68: 218-28). Since the mid 1990s, manufacturers have been under pressure to remove this chemical from their vaccines, but progress has been frustratingly slow. A recent review suggested that some infants receiving thimerosal preserved vaccines may be exposed to cumulative levels of mercury higher than those considered to be safe (Pediatrics, 2001; 107: 1147-54).Formalin is a dilute formaldehyde solution used to inactivate viruses and detoxify toxins. Nearly 50 studies have shown a link between formaldehyde exposure and leukaemia and cancers of the brain, colon and lymphatic tissues (Neustaedter R, The Vaccine Guide, Berkley, CA: North Atlantic Books, 1996).
Aluminium sulphate an adjuvant used to boost the effectiveness of a vaccine. Studies show that aluminium containing vaccines cause more reactions than others.
Also common are phenol, a disinfectant and dye; ethylene glycol, the main ingredient in antifreeze; benzethonium chloride, an antiseptic; and methylparaben, a preservative and antifungal known to have hormone disrupting qualities.
Last year, it was revealed that vaccines contain a new danger. Many vaccines manufactured in the late 1980s and early 1990s were made using bovine products obtained from countries where bovine spongiform encephalitis (BSE) was a substantial risk.
In the US, the FDA has repeatedly asked pharmaceutical companies not to use materials from cattle raised in countries where BSE is a problem. However, according to a recent report in the New York Times (8 February 2001), five companies, including GlaxoSmithKline, Aventis and American Home Products, were still using these ingredients in 2000 to make nine widely used vaccines, including those for polio, diphtheria and tetanus.
In the UK, the Daily Express (2 May 2000) reported that seven vaccines (including those for polio, diphtheria and tetanus) given to children during 1988-1989, and manufactured by SmithKline and Wellcome, were made from potentially contaminated bovine products. Later that year, the Mirror (21 October 2000) reported that the polio vaccine made by Medeva and in current use had been recalled due to possible contamination with bovine products.