DodetB,FooksAR,MüllerT,TordoN,andtheScientific&TechnicalDepartmentoftheOIE(eds): TowardstheEliminationofRabiesinEurasia.DevBiol.Basel,Karger,2008,vol131,pp291-298. The Strength of 70%: Revision of a Standard Threshold of Rabies Control H.-H. Thulke, D. Eisinger UFZHelmholtzCentreforEnvironmentalResearch,UFZ,DepartmentofEcological Modelling, Leipzig, Germany Key words: rabies, foxes, vaccination, herd immunity, control planning, modelling Abstract: Thesuccessoforalvaccinationoffoxes(ORV)conceptuallyislinkedtotheimmunisation ofhostindividualsbeyondtheherdimmunitythreshold.However,fieldevidenceandtheoretical analysissuggeststhatmathematicallyderivedvaluesofherdimmunitymightberatherconservative and,moreover,restricttheadjustmentofstandardORVprotocolsinthecaseoflimitedresources. Here,therelationshipbetweenbaitingeffort,durationofORVprogrammesandrabieselimination is analysed. An individual-based, spatially explicit model for the control of rabies in foxes that incorporates the important peculiarities of the vaccination process, i.e. the spatial distribution of infected hosts, irregular home-range use, heterogeneous bait coverage etc., is applied. Using multiple repetitions of simulated ORV programmes, the control outcome is analysed in a chance-like fashion overriding the yes-or-no prediction inherent in the herd immunity concept. It is shown why control planning must not only aim at particular immunisation levels but, simultaneously, has to specify the allowed time horizon of control success. It is demonstrated thatplanningahigherchanceofeliminationincreasesnecessaryeffortnon-linearly.Itwasfound that low immunisation results (i.e. 50%) still provide a reasonable chance of control success. ThepotentialchangesinORVplanningandevaluationallowingfortheintegrationofriskconcepts in strategies are discussed. INTRODUCTION Rabiesisstilloneofthemostseriouszoonosesintheworld[1].Nevertheless, thecombatofwildliferabiesbymeansoforalvaccination(ORV)representsoneof the success stories of disease control. The development of the vaccine and its encapsulationinbaits[2],innovativefieldapplication[3]andthesupportoflarge- scaleelimination[4]haveresultedinthetriumphofdiseasemanagementmethods sincetheearly1980s.ORVprogrammeshavebeenconductedinEurope[5],Canada [6],andtheUnitedStates[7].Afterthreedecadesofefficientcontrol,however,cost 291