R. Morrison state, "there are no basic differences between the physiology of laboratory animals and humans." According to Botting and Morrison, through animal testing, "[S]cientists have established causes of and vaccines for dozens of infectious diseases, including diphtheria, tetanus, rabies, whooping cough, tuberculosis, poliomyelitis, measles, mumps, and rubella." Researchers also gain knowledge of general surgical and transplantation techniques by using animal models.

The progression of medical science over the past two centuries might have slowed or stopped if every researcher's theories required experiments on human subjects first. As Carl Cohen states, testing new vaccines and drugs "unavoidably risks the well-being, sometimes even the lives of the first experimental subjects." Cohen concludes that "[h]uman health needs morally justify" using animals first. Countering concerns about testing on animals like dogs, cats, and primates, Cohen and Frederick K. Goodwin note that the overwhelming majority of animals used today are rodents bred for biomedical research.

Some argue that with new methods available, even rodents are unnecessary. According to Lawrence Corey, in the past 20 years, alternatives, including elegant cell culture models and computer models, have created "real changes" and reduced the need for animals. Some drugs may be tested first in bacteria developed for this purpose. Yet Corey says the results can be "imperfect at best." Cohen is less diplomatic, calling large-scale replacement of animals "a misleading fantasy." Though alternatives suffice in some cases, there is no substitute for testing the whole animal in others. As Cohen states, dangerous side effects may appear "only in the living organism and its complicated network of constituent organs, as they actually function." Without studying the entire system, researchers lose valuable information.

This thought makes Goodwin worry that researchers "made a very bad tactical error" by agreeing to reduce numbers, replace animals, or refine techniques, because it "suggested [they] might be doing something morally wrong." He thinks "human beings have the right to use animals for their purposes," if animals are treated humanely. Researcher Stuart Derbyshire thinks that deliberate mistreatment is unnecessary, but "further concern for the animals' wellbeing is beside the point." Researchers should not apologize for prioritizing human needs.

Human health depends on knowledge gained via experiments on animals. Current research on vaccines for diseases like AIDS and malaria, or studies on regeneration of nerve cells in the spinal cord, would slow or stop, because if research is not performed on animals, the potential subjects must be human.

Resources
Botting, Jack H., and Aaron R. Morrison. "Animal Research Is Vital to Medicine." The Rights of Animals. Ed. Auriana Ojeda. San Diego: Greenhaven Press, 2004.
Cohen, Carl. "Animal Experimentation Is Necessary." Animal Rights. Ed. Shasta Gaughen. San Diego: Greenhaven Press, 2005.
Corey, Lawrence. "Animal Testing Is Essential for Medical Research." Animal Experimentation. Ed. Cindy Mur. San Diego: Greenhaven Press, 2004.
Derbyshire, Stuart. "Animal Experimentation Is Justified." The Rights of Animals. Ed. Auriana Ojeda. San Diego: Greenhaven Press, 2004.
Goodwin, Frederick K. "The Animal Rights Movement Threatens Medical Progress." Animal Experimentation. Ed. Cindy Mur. San Diego: Greenhaven Press, 2004.

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