Most US research on chimpanzees is unnecessary and should be strictly limited in the future, an independent panel of medical experts said Thursday, stopping short of urging an outright ban. While Europe ended research on great apes in 1999, the United States has continued to allow medical studies on chimps in areas ranging from HIV/AIDS vaccines, hepatitis C, malaria, respiratory viruses, brain and behavior. While controversial, these studies are also quite rare, making up just 53 of the 94,000 active projects sponsored by the National Institutes of Health in 2011, or 0.056 percent of all federally funded US research. An NIH proposal to reintroduce several dozen retired chimpanzees into research colonies last year caused mounting public outcry and led to the review of chimp research by independent medical experts at the Institute of Medicine. \"The committee concludes that while the chimpanzee has been a valuable animal model in the past, most current biomedical research use of chimpanzees is not necessary,\" said the IOM in its report. The NIH should therefore limit the use of chimps to biomedical research in which there is no other model available, that could not be performed ethically on humans, and would hinder progress against life-threatening conditions if halted. Chimps are still necessary in the development of vaccines against hepatitis C, for short-term continued study of monoclonal antibody research against bacteria and viruses, and for comparative genome studies and behavioral research, the IOM said. When chimpanzees are used for these ends, the studies should \"provide otherwise unattainable insight into comparative genomics, normal and abnormal behavior, mental health, emotion, or cognition,\" the report said. In addition, all experiments must be performed \"in a manner that minimizes pain and distress, and is minimally invasive.\" US research on chimps is mainly conducted at four facilities: the Southwest National Primate Research Center, the New Iberia Research Center at the University of Louisiana-Lafayette, the Michale E. Keeling Center for Comparative Medicine and Research of the University of Texas MD Anderson Cancer Center, and the Yerkes National Primate Research Center at Emory University. As of May, there were 937 chimpanzees available for research in the United States. The US government supports 436 of them, and the rest are owned and used for research by private industry. The IOM noted that since the NIH called for a moratorium on breeding chimps for research back in 1995, the US federally funded research population will \"largely cease to exist\" by 2037. European Union facilities have not conducted any research on chimps since 1999, and a formal ban on using great apes in research -- including chimpanzees, gorillas, and orangutans -- was issued last year.