Biomedical research still relies on laboratory animals to conduct basic research and to be able to continue developing effective and safe medicines, vaccines, and other treatments. Clinical and applied research in turn relies on the findings from basic research. In addition, there are scientific questions that cannot currently be researched using alternative methods.
Despite claims to the contrary, animal experiments provide more certainty. Without them, for example, drugs whose effects have been studied in cell cultures or computer models would have to be tested directly on humans. Drug testing is primarily about gaining information about the mode of action and behaviour of an active substance in a living being that is similar to humans. For ethical reasons, it is forbidden to expose humans to the risk of such tests. The risk of an undesirable effect of a substance is very high for humans if it has not been tested in animal experiments for its safety to prove that it is harmless.
Only if there is sufficient information on the effect and harmlessness, which is also based on studies in several animal species, can reasonably reliable conclusions be drawn about the effect in humans. Although this does not give a 100% guarantee for the safety of a substance in the human body, it will with a high probability protect human test subjects from unacceptable, severe side effects.
Besides, which doctor would want to take the risk of causing life-threatening damage in a human being when testing a new substance? Which test subjects would be willing to take a drug whose safety and efficacy had not first been tested in another living organism, i.e. in animal experiments? To protect humans, such steps are required by law. New medicines and surgical treatments must first be tested on animals before they can be tested on humans under high safety standards. These worldwide ethical principles of human medicine were established after the Second World War (Nuremberg Code; today: of Helsinki) so that human experiments as were carried out in concentration camps in Nazi Germany would never be possible again.
Only partial aspects of the effect of a drug can be investigated in cell or tissue cultures. These partial aspects are also investigated with such in vitro methods within the framework of drug research and development. However, this is usually not sufficient. The body is highly complex; the various organs, cells, metabolic or hormonal systems are interconnected in an infinite number of "feedback loops". For the safety of patients and for the development of better treatment methods, it is therefore important that a drug or a certain treatment is tested in the body itself. For example, a drug may have a different effect on the heart if part of the active ingredient has been changed in the liver. Therefore, researching substances in the living body is essential.