estimated from actuarial data. No amyloid deposition was found in the one biopsy and four postmortem examinations performed.

Summary and conclusions on the Fort Detrick studies. There were no clinical sequelae (e.g., neoplasms, amyloidosis, autoimmune diseases) attributable to intense long-term immunization in this well-studied cohort. None of the subjects suffered unexplained clinical symptoms requiring them to take sick leave that could be attributed to the vaccination program. There was some evidence of a chronic inflammatory response, as characterized by certain laboratory test abnormalities: elevated levels of hexosamine (an acute-phase reactant), slightly abnormal white cell counts, slightly abnormal liver function test results, and polyclonal elevations in levels of gamma globulins. However, these changes cannot necessarily be attributed to the vaccinations, since the workers studied were occupationally exposed to a number of virulent microbes.

This series of longitudinal clinical studies had several shortcomings. There was no comparison cohort and no attempt to make the employees in the study representative of the broader population of workers. Further, the outcomes may be due in part to the healthy-worker effect since the subjects were selected for the intensity and length of their vaccination history, and individuals who either left employment or discontinued the vaccination program were not considered. Thus, the studies may have inadvertently focused on the most resilient individuals. However, the Fort Detrick study is valuable because careful monitoring did not disclose any evidence of serious unexplained illness in a cohort that received a series of intense vaccination protocols over many years.

Gulf War Veterans

Several studies of Gulf War veterans have looked for associations between health outcomes and exposure to a variety of agents, including vaccinations. The methodology and general results of these studies are described in Chapter 2.

U.K. Gulf War Veterans. Unwin and colleagues (1999) reported the results of a large cross-sectional postal survey on a random sample of U.K. Gulf War, Gulf War era, and Bosnia conflict veterans. The Gulf War and Bosnia troops were vaccinated against hepatitis A and B, yellow fever, typhoid, poliomyelitis, cholera, and tetanus (routine vaccinations), as well as against biological warfare agents (plague, anthrax administered simultaneously with the pertussis vaccine). Of the Gulf War cohort (n = 3,284; response rate = 70.4 percent), 31.8 percent reported that they had their vaccination records. The study found no difference between veterans with and without vaccine records regarding age, education, health outcomes, or rank, except that those with records were more likely to be reservists. A substantial fraction, 61.9 percent, of Gulf War veterans reported symptoms of the multisymptom syndrome (characterized by fatigue, mood or cognition, or musculoskeletal symptoms) using the CDC criteria (Fukuda et al., 1998). The study found that having received any routine vaccination



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