rate tests by polymerase chain reaction assay, conducted at Charles River Tektagen, a commercial facility, showed no presence of mycoplasma DNA in any of the samples.
Some Gulf War veterans and others have expressed concerns about whether squalene might be present in the anthrax vaccine and whether it has the potential to cause health effects. Squalene is a hydrocarbon compound found in many natural sources, including olive oil and the human body. In humans it is a precursor in the synthesis of cholesterol and is also found in oils of the skin (Kelly, 1999; Final Report, 1982). In the 1970s the average dietary intake of squalene was calculated to be 24 milligrams (mg) per day in a 2,000-calorie diet (Liu et al., 1976). Among people whose diets include more olive oil, squalene consumption can range from 200 to 400 mg/day (Smith, 2000). Roughly 60 percent of the squalene consumed in the diet is absorbed through the gastrointestinal tract; much of what is absorbed is converted into cholesterol (Strandberg et al., 1990).
The IOM Committee on Health Effects Associated with Exposures During the Gulf War (IOM, 2000b) examined in detail evidence regarding the potential health effects of squalene, including those that might be related to its use as a vaccine adjuvant. In the United States, it has been tested in animal studies of anthrax vaccine and in human studies of other vaccines (GAO, 1999a; Ivins et al., 1995; Ott et al., 1995), but it is not used in any human vaccine currently in use in the United States. An influenza vaccine with squalene as an adjuvant has been approved and distributed in Europe and has not been associated with adverse health events. The prior IOM (2000b) review resulted in the conclusion that, in certain animals and under selected conditions, squalene has been found to produce arthritis and neuropathology, but it also resulted in the conclusion that the relevance of toxicity findings for animals to humans is uncertain, in part because humans absorb squalene differently from animals. The human studies testing a squalene-containing adjuvant in other vaccines found only transient acute effects.
DoD sponsored a study by SRI International, a private company, to assay AVA and other pharmaceuticals for squalene at the level of parts per billion. The study report, dated August 14, 2001, found that 1 lot of over 30 lots tested contained measurable levels of squalene. Three samples from that lot contained squalene at 7, 9, and approximately 1 parts per billion, respectively. Use of vaccine from that lot has not been associated with elevated rates of adverse events (see the discussion of the Special Immunizations Program in Chapter 6).