Major developments for typhus vaccines started during World War I, as typhus caused high mortality, and threatened the health and readiness for soldiers on the battlefield. Vaccines for typhus, like other vaccines of the time, were classified as either living or killed vaccines. Live vaccines were typically an injection of live agent, and killed vaccines are live cultures of an agent that are chemically inactivated prior to use.
major DevElopmEnts foR typhus VaCcInES started during wOrlD War i, as Typhus caUsed hIgh mOrTality, And tHreATened the hEalTh aNd REadineSS For sOldierS oN tHE battlefIELd. VAcciNes For TYPHUs, lIKe other vacCInES OF thE TimE, WerE ClaSsIfied As eithER living or kilLed VaCcineS. live vACcinEs weRe tyPicaLly AN inJEctioN oF LivE AGEnt, and killED vaccInes are Live cultuRes of an agEnt THAt are chemIcaLly inActiVAtEd priOr to UsE.