Computers are an essential partner of biomedical research, enabling mathematical modeling, database analysis and computer simulations. Scientists use computational methods to analyze large volumes of historical experimental data to guide the design of their own experiments. And they compile large volumes of experimental data into virtual biological systems and networks that may reveal new insights for their research questions.
But, computer modelling can only be done if there is enough information to put in the model. There is no way of acquiring this information other than going into a living organism to look for it. In vitro experiments, which are done with molecules (like proteins or DNA) or cell cultures, are very good to unravel mechanisms that happen inside the cell, but are not always so useful to find out, for example, how different cells, tissues and organs interact inside the body. For the foreseeable future, we will need to use live animals to answer some of the most important scientific questions related to human health.