volunteers (older than 65 years) received the adjuvanted vaccine, and 823 elderly volunteers received a conventional influenza vaccine. More than 20 percent of the volunteers who received the adjuvanted vaccine had local reactions. Myalgia was the only systemic effect to have been significantly more common in those receiving the vaccine with a squalene-containing adjuvant (3.9 percent) than those receiving the vaccine without the adjuvant (1.8 percent). All adverse events were recorded for 1 week after vaccination. Hospitalization and mortality were followed during the influenza season. The group receiving the adjuvanted vaccine had similar hospitalization rates and lower mortality than subjects receiving the conventional vaccine.
To date, clinical studies of the MF59 adjuvant that contains squalene have not shown any adverse health effects beyond transient acute effects.
A recent study by Asa and colleagues (2000) reports on the development of an anti-squalene antibody assay to detect antibodies to squalene in the circulation. Blood samples from 144 Gulf War era veterans or military employees, 48 blood donors, 40 patients with systemic lupus erythematosus (SLE), 34 patients with silicone breast implants, and 30 patients with chronic fatigue syndrome (CFS) were studied for squalene antibodies. The study reports that a blinded test of serum samples found antibodies to squalene in more than 95 percent of 38 veterans deployed to the Gulf War who developed chronic illness symptoms; in all of the 6 veterans not deployed to the Gulf War who developed chronic illness symptoms; and in none of 12 veterans deployed to the Gulf War who were healthy. In an unblinded test, the study reported antibody reactivity to squalene in 5 percent of blood donors, 10 percent of patients with SLE, 10 percent of patients with silicone breast implants, and 15 percent of patients with CFS.
This study has several shortcomings. The subjects were self-selected, rather than being chosen at random from a larger sample, which can introduce substantial selection bias and does not allow inferences to the broader population of Gulf War veterans. Sample sizes were small, and the study may suffer from misclassification errors since the group of Gulf War veterans categorized as healthy (n = 12) was not devoid of individuals with serious symptoms (1 had fibromyalgia, 1 had thyroid disease, 3 had memory loss, and 4 had chronic fatigue). Further, the report provides inadequate evidence that the assay is able to accurately detect antibodies to squalene. Many of the methods used in the study are not described; as a result it is not possible to fully assess the study’s methodology or to reproduce the assay. The study did not attempt to demonstrate that the substance giving the positive response in the assay was found in the immunoglobulin G (IgG) fraction of serum where antibodies are found. Further, the authors did not show that the assay was specific to squalene. To prove the specificity of the assay, the investigators would have had to show inhibition, in a dose–response manner, with squalene and no inhibition with other substances, as is seen in most reports of new enzyme-linked immunosorbent assays (ELISAs).