A CDC epidemiologist noted that no unique laboratory diagnosis or clinical syndrome has been identified for most of the rare, serious outcomes associated with vaccination. Without the ability to define uniquely such adverse events, it will be difficult to link them to specific genetic markers. He added, however, that such analysis is feasible for adverse events that are more common, such as seizures, with the use of the LLDB. By genetically analyzing tissue or blood samples from those individuals who developed seizures following vaccination with DPT, for example, and comparing them with samples from matched controls who did not react adversely to vaccination, researchers might discern a genetic marker for susceptibility to seizures following vaccination with DPT.

Fisher delineated five research areas that she felt, from a parent's perspective, were important to pursue. One was research to evaluate, on a molecular biology level, the impact over time of repeatedly manipulating the human immune system with single and multiple antigens. Parents who are being asked or required by law to vaccinate their children with increasing numbers of vaccines, she pointed out, want it known what exactly is happening in the human body at the molecular level when several vaccines are given simultaneously or over a short period of time, compared to physiologic responses to naturally-presented antigens, such as those found in the viruses or bacteria against which the vaccines are directed.

The way in which an antigen is presented to the body, including whether in a vaccine or through natural infection, could affect the immune response. The route of immunization with DNA vaccines, for instance, could influence the type of cytokine response elicited by the vaccine. 23 In addition, the immune response to multiple antigens given simultaneously could be different than the response to the same antigens given individually (Goldenthal et al., 1995). A representative of a vaccine manufacturer said that studies are being conducted to assess some of the short-term immunologic effects of vaccines given separately versus the effects of those given simultaneously.

Consumer advocates also question whether there are differences in long-term immunologic function and health status between children who receive vaccinations and those who do not. Several vaccine manufacturer representatives and biomedical researchers noted that it would be a challenge to conduct studies aimed at assessing the long-term immunologic effects of vaccination versus nonvaccination. It is difficult to find for such studies a group of nonvaccinated children who are similar in all relevant aspects to vaccinated children, an epidemiologist pointed out. Other researchers noted that even if immunologic differences are detected between vaccinated and nonvaccinated

23  

Based on data presented at the International Meeting on Nucleic Acid Approaches for the Prevention of Infectious Diseases, Bethesda, Md., February 5–7, 1996.



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