The present invention relates to a method for reducing the occurrence and severity of infectious diseases, especially infectious diseases in which lipid-containing infectious organisms are found in biological fluids, such as blood. The present invention employs solvents useful for extracting lipids from the lipid-containing infectious organism, thereby reducing the infectivity of the infectious organism. The present invention uses optimal solvent systems such that the lipid envelope around the viral particle is dissolved while the viral particle remains intact, resulting in a modified viral particle. The present invention also provides an autologous vaccine composition, comprising a lipid-containing infectious organism, treated with solvents to reduce the lipid content of the infectious organism, combined with a pharmaceutically acceptable carrier. The vaccine composition is administered to an animal or a human to provide protection against the lipid-containing infectious organism. The present invention further provides a simple, inexpensive and easy to use kit for delipidating fluids and for delipidation of lipid-containing organisms in a fluid.