vaccine may contain attenuated microorganisms, killed microorganisms or toxoids. Certain vaccines contain attenuated forms or killed forms or toxoids. For example, in case of cholera, rabies, hepatitis B, Japanese encephalitis, we use killed form. Why can't we form attenuated forms here? Is it because the diseases are so deadly that usage of attenuated forms can cause the death of the recipient of the vaccine. But, if it is attenuated isn't it true that the life form has lost it's toxic properties and is still being able to produce antibodies? So what exactly is the significance of using killed microbes for these particular diseases?