Understanding Vaccine Economics with...
Transcript of Understanding Vaccine Economics with...
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
UnderstandingVaccineEconomicswithSimulationsAuthors:DavidBishaiandSasmiraMattaLearningObjectives:• TounderstandthePhilipsoneffectorratherhowacceptabilityofavaccineis
determined• Tounderstandthedifferencebetweencostversusbenefit• Tounderstandthereisnorightanswerindetermininghowtogoaboutdecision-
making• Tousesimulationstobetterunderstandvaccineeconomics
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
UnderstandingVaccineEconomicswithSimulationsAuthors:DavidBishaiandSasmiraMattaInthisexercise,youwillbeusingfoursimulations.Onewillexaminethedynamicsinasinglecountry,andtheotherthreewillexaminethedynamicsofneighboringareas.YouwillbeusingtheForiosoftwaretoanalyzehowthepopulationofinfectedchildrenandthecoveragechangesasaresultofdifferentscenarios.SingleCountryModel:Thefollowingdiagramisacausalloopdiagram.Itrepresentsthedynamicsthatareoccurringinasingularcountry.FigureI.
Inordertounderstandthisdiagram,itisimportanttounderstandwhatisincludedinthemodel.ThisisamodifiedSIRmodel,whereSIRisanacronymforSusceptible,Infected,andRecovered.ASIRmodelisanepidemiologicalmodelthatcomputesthetheoreticalnumberofpeopleinfectedwithacontagiousillnessinaclosedpopulationoftime[1]. Thearrowsshowthedirectionofinfluenceforeachvariable.Sincewearealsomeasuringvaccinecoverage,thismodelalsotracksthenumberofchildrenwhoreceivethevaccine.Inthemodel,wehavefourboxedvariables:SusceptibleS,InfectedI,RecoveredR,andImmune.Eachofthesevariableswillcomputethenumberofchildrenwhofallintoeachcategoryateachpointintime.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
Thearrowswiththelargerheadsandrectangularbodiesaretheflowsandtheyrepresenttherates.Inthismodel,wehavefourflows:getsinfected,getsbetter,getsvaccinated,andimperfectvaccination.Eachoftheseflowsmeasurestherateatwhichachildmovesfromoneboxtoaconnectingbox.Ex.Ifwesaythattherateof“getsvaccinated”is80/1000,thismeansthatforevery1000children,80willgetvaccinatedateachtimestep.Theothervariablesthatareconnectedtothediagrambythesmallerarrowsareotherimportantfactorsthatinfluencetheboxedvariablesandtherates.Thefollowingtablesummarizesthevariablesusedintheabovediagramandtheelementstheymeasure.TableI.DiagramKeyDiagram DefinitionSusceptibleS Measuresthenumberofchildrenthat
aresusceptibletomeaslesInfectedI Measuresthenumberofchildrenthat
areinfectedwithmeaslesRecoveredR Measuresthenumberofkidswho
recoverafterhavingthemeaslesImmune Measuresthenumberofchildrenwho
receivethevaccinationGetsInfected Rateatwhichasusceptiblechildgets
sickwithmeaslesGetsBetter Rateatwhichaninfectedchildrecovers
frommeaslesGetsVaccinated Rateatwhichsusceptiblechildrenget
vaccinatedImperfectVaccination Rateatwhichvaccinationisimperfect
anddoesnotpreventdiseaseforchildInfectionProbability Likelihoodofbeinginfectedwith
measlesRecoveryTime Timeittakesforachildtorecoverfrom
measlesAcceptability Measuresthecountry’sperceptionof
vaccinesafetyandefficacyVaccineCoverage Proportionofchildrenthatare
vaccinatedProbabilityofaMishap Probabilitythatthevaccinewillnot
induceimmunityThefollowingsimulationshavebeendesignedtoreinforcedifferenttopicsinvaccineeconomics.Whenansweringquestionfocusonchangesandshift,anddonotgetstuckonwhetherornotdifferencesaresignificantunlessotherwiseasked.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
SIMULATION1:UnderstandingthePhilipsonEffectThePhilipsonEffectisatheorystatingthatasavaccinepreventablediseasedisappears,sotoodoesthedemandforvaccines.Inotherwords,asadiseasebecomeslessprevalent,parentsarelesslikelytogettheirchildrenvaccinated[2].AccordingtoGeoffardandPhilipson,thedemandforavaccineisproportionaltothebenefitofbeingvaccinated.Theypointoutthatifanindividualrealizesthatcoverageisveryhigh,arationalpersonwouldrealizethatherdimmunityisprotectingthemandthattheirpersonalbenefitfromavaccinationislow.Arationalandselfishpersonwouldbelessandlesslikelytowantavaccineastheriskofdiseasegoesdowntothepriorsuccessofthevaccineprogram.Intheseexercises,wewillconsideravaccinetobeperfectifitwilldefinitelyimmunizeachild.Therefore,everychildwhoisvaccinatedwilldefinitelybeimmunetothedisease.Ontheotherhand,animperfectvaccineisavaccineinwhichthereisachancethatachildwillnotbeimmunetoaparticulardiseaseevenifthechildreceivesthevaccine.Inthissimulation,youwillbeabletotrackthreethings—theinfectedpopulation,vaccinecoveragewiththePhilipsoneffect,andvaccinecoveragewithoutthePhilipsoneffect.Asyourunthesimulation,focusonhowthecoveragecurvesdiffer.1.Gotothewebsitehttps://forio.com/simulate/smatta1/single-country2.Youshouldseethefollowingonyourscreen
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
3.Clicktheresetbutton.Startwiththeslidertoolontheperfectvaccinesetting.
4.Clicktheadvancebuttonsixtimessothatthesimulationrunstocompletion.Thisiswhatyoushouldseeonthescreen.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
Whichvaccinecoveragecurveresemblestheinfectedpopulationcurve?Doesthismakesensetoyou?Explain.ThecoveragecurvethattakesthePhilipsonEffectintoconsiderationfollowstheinfectedpopulationcurve.ThismakessensebecauseasthePhilipsonEffectindicates,astheinfectedpopulationincreases,sodoesthecoverage.Astheinfectedpopulationdecreases,sodoesthecoveragerate.Ontheotherhand,thevaccinecoveragecurvewithoutthePhilipsoneffecthasadifferentcurvature,whichmeansthatthecoverageischangingatadifferentratefromtheinfectedpopulationcurve.ThismeansthatthecoveragewithoutthePhilipsoneffectisbeingmeasureddifferently.5.Clicktheresetbutton.Movethedecisionsliderallthewaytotherighttotheimperfectvaccinationsetting.Nowclicktheadvancebuttonuntilthesimulationfinishesrunning.Afterrunningthroughthesimulation,youshouldseethefollowingonyourscreen.
HowdoesthePEAKoftheinfectedcurvedifferwithrespecttotheprevioussimulation?Aretheremoreorlesschildrenwhoareinfected?Explain.Undertheperfectvaccinesettingwesee725childrenareinfectedwhereasintheimperfectvaccinesettingweseethat736childrenareinfected.Therearemore
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
childreninfectedwhenthevaccinedoesnotworkaswell,whichmakessensebecauseitdoesnotguaranteefullimmunity.Inthesimulation,youseethatwhenthevaccineisimperfect,about11morechildrenwillgetinfected.Ifparentsstartseeingthattheirvaccinatedchildrenareinfactgettingsick,atwhatpointdoesthisposeaproblem?Howcanyoucommunicatevaccineefficacytoparents?Participantsshouldusetheirownexperiencestoanswerthisquestion.Underwhichsettings—PhilipsonorNoPhilipsoncurvesdoweachievemorecoverage?Whycouldthisbethecase?WhenweoperatewithoutconditionsofthePhilipsoneffect,weachievemorecoverage.ThisisthecasebecausewhenweconsiderthePhilipsoneffect,parentsarechoosingwhetherornottovaccinatetheirchildrenbasedonthediseaseprevalence.WithoutthePhilipsoneffect,weassumethatthecoveragerateisindependentofdiseaseprevalence.NowthatwehaveseenthatthePhilipsoneffecthasthepotentialtodrasticallychangethecoverage,whatdoyoudo?Howdoyouworkandcommunicatewithparentsandconvincethemthattheyshouldbegettingtheirchildrenvaccinated?Howdoyoupreventthemfromworrying?Itwouldbegreattotalkaboutthisquestionasagroup.Participantsmighthaveinterestingexperiencestoshareandtalkabout.NowthatwehavewalkedthroughthePhilipsoneffectunderbothperfectandimperfectvaccineconditions,itisnowtimetomovetoatwo-countryscenario.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
TherewasabotchedmeaslescampaigninDistrictAwhere15childrenwhoreceivedthevaccinationdied.Itwasreportedthatthevaccinationswerenotstoredproperly,andthattheneedleswereusedmultipletimes.YouareinchargeoftheEPIofficeinDistrictB.DistrictAneighborsDistrictB.YouareresponsibleforimprovingmeaslescoverageinDistrictB,especiallynowthatparentsarewearyofgettingtheirchildrenvaccinatedafterhearingthenews.Thenexttwosimulationsfollowsimilardynamicsaswehavealreadyseeninthesingularcountrycausalloopdiagram.Infact,ifyoulookatthemodelbelow,thesinglecountrymodelwascopiedandpastedtwice.Ontheleft-handside,wehaveDistrictA,andontheright-handsidewehaveDistrictB.FigureII.AMoreDynamicModel(LeftSideRepresentsDistrictAandtheRightSideRepresentsDistrictB).
Therearetwomaindifferencesthatdistinguishthetwo-districtmodelfromthesinglecountrymodel.I)ThereisacommunicationvariablewhichisdenotedasCommforDistrictAandComm0forDistrictB.Thisvariablecontrolswhetherornotthecommunicationorthedisseminationofinformationsurroundingvaccinesispositiveornegative.II)ThereisanarrowgoingfromDistrictA’sAcceptabilitytoDistrictB’sAcceptabilityandviceversa.Thisdemonstratesthetransmissionofinformationbetweenthedistricts—informationtravels!Whatsocial,cultural,andmediaeventsareexamplesofnegativeinformationonvaccineacceptance?Whilestudentswillprobablyhavemanydifferentanswersforthisquestion,itisimportantthattheyunderstandthatnegativeinfluencewillleadtodecreasedacceptabilityofvaccines.Ifastudentisstuckthekeyquestiontoaskis“whatcanyouintroducethatwilldriveacceptabilitydown?”
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
Possibleanswersinclude(butarenotlimitedtothefollowing):Witchdoctorsadvocatingforchildrentonotbevaccinated,botchedmeaslescampaigninthecountry,governmentwarningagainstvaccinationofchildren,etc.Whataresocial,cultural,andmediastrategiesareexamplesofpositivecommunicationonvaccineacceptance?Similartothequestionabove,ifastudentisstuck,encouragethestudenttothinkaboutwhatwouldincreaseacceptabilityinacountry.Possibleanswersinclude(butarenotlimitedtothefollowing):Governmentadvocatesforvaccinations,publicfigures(likecelebrities)advocateforvaccinations,religiousleadersadvocateforvaccinations,etc.Nowwewillexplorethetwo-districtmodelonForiointhreescenarios,whichareoutlinedbelow.RememberthatineachofthefollowingscenariosyouareintheEPIprogramofDistrictB.SIMULATION2:DoNotCensortheMediaInthissimulation,youhavedecidedtocensorthemedia.ThismeansthatthebadnewsaboutbotchedmeaslesvaccineinDistrictAcannotreachDistrictB.Inthissimulation,youcanmanipulatethecommunicationsurroundingvaccinesinthedistricts.Themorenegativethecommunicationis,themoreyoucandecreaseacceptabilityinthecountryandviceversa.TheBotchedVaccinesinDistrictAslidercanbeadjustedtoindicatetheseverityofthebotchedcampaigninDistrictA.TheBotchedVaccineinDistrictAwillaffecttheprobabilityofavaccinemishap.Themoresevereitis,themoreimperfectthevaccineis,andthemoreproblemsitwillcause.Ifyouhoveroverthecurves,thetooltipwilltellyouthecountrythatyouarelookingatandthevalueatthemoment.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
1.Gotohttps://forio.com/simulate/smatta1/south-sudan-and-uganda-1.Thefollowingisanimageofwhatyoushouldseeonthescreen.
2.Setthecommunicationinbothcountriesto0.SettheBotchedVaccinesinDistrictAtotheleftmostLessSevereSetting.Advancethesimulationtotheend.Thisiswhatyoushouldseeonthescreen.
Atapproximatelywhattimedoesthepeakoftheinfectionoccur?4.5monthsWhatisthemaximumvaccinationincoverageinDistrictBatthetimeofthepeakoftheinfection?(Sincethelinesarequiteclosetogether,youmayusetheDistrictA’sestimateforDistrictBifyouareunabletohoverovertheDistrictBcurve).
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
~.49coverage3.SettheBotchedVaccinesslidertotherightmostsideortheMostSevereSetting.Keeptheinfluenceinbothcountriesat0.Thisiswhatyoushouldsee.Advancethesimulationtotheend.
WhatisthecoverageinDistrictBatthepeakoftheinfection?~.47NotetoInstructors:ItisveryimportantthatusersseethatthereisadecreaseincoverageinDistrictB!Youshouldbeseeingadecreaseincoverage.Ifnotjustplayaroundwiththetooltipuntilyoudo.Explainthedecreaseincoverage.Usethemodeltohelpyourreasoning.IfthemeaslescampaigninDistrictAisreallybotched,thenitbecomeslessacceptabletovaccinatechildren.Withacceptabilitydecreasing,fewerchildrenwillbevaccinated,andmorechildreninDistrictAwillbeinfected.AstheacceptabilityinDistrictBisinfluencedbytheacceptabilityinDistrictA,theacceptabilitywillalsotakeahitinDistrictB.Thisiswhyatthepeakofinfectionthecoverageisslightlylower.Thepurposeofthissimulationistounderstandthatthenewsofabotchedmeaslescampaigncanaffectthewillingnessofparentstovaccinatetheirchildren.4.NowchoosetheintensityofthebotchedvaccinesinDistrictA.Asyouadvancethesimulation,changetheinfluenceinDistrictB.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
Ifyouinducepositivecommunication,howwillthisaffectcoverageinDistrictB?Ifyoutakeawayinducenegativecommunication,howwillthisaffectcoverageinDistrictB?UserswillbeabletoseethatpositiveinfluenceshouldbringupthecoveragedespitewhatishappeninginDistrictA.Thisisbecausewecanbuyacceptabilityinasense.Wearetellingparentsignorewhatishappening,andfocusonthegoodofvaccines.Wecanalsobuynegativeacceptabilityandcontinuetoshowparentsthatvaccinesarenotgood.Thiswouldbringthecoveragedown.HowdoeschangingtheinfluenceinDistrictAaffectthecoverageinDistrictB?UserswillseeastheyincorporatenegativeinfluenceinDistrictA,theDistrictBcoveragewillgodown.UserswillseethatastheyincorporatepositiveinfluenceinDistrictA,thecoveragewillincrease.Withthesevisualizations,wherewouldyouallocatemoneytoimprovevaccinecoverageinDistrictB?Inotherwords,doyouthinkitismoreeffectivetoputmoneyintoinfluenceinDistrictAorintoDistrictB?Howwouldyouarriveatthedecision?Thisisuptotheuser.Instructorsneedtostressthatwewanttoputourmoneyintowherewethinkwewillseethelargestpositiveeffect.Whatareyourfinalthoughtsonthissimulation?Letusersusethisspacetowritedownanyburningquestionsorthoughtthatcanbediscussedlaterasagroup.Nowlet’smovetothenextsimulation!
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
SIMULATION3:CensortheMedia1.Gotohttps://forio.com/simulate/smatta1/south-sudan-and-uganda. Thisiswhatyoushouldseeonyourscreen.
2.Nowresetthesimulation.Clickdonotcensormedia.Keepthebotchedvaccinesettingattheleftmostlessseveresetting.Keepbothcommunicationvariablessetto0.Advancetotheendofthesimulation.Thisiswhatyoushouldseeonthescreenwhenthesimulationfinishesrunning.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
3.Nowmaintainthesamesettingsasbefore(bothcommunicationsshouldbesettozero,lessseverebotchedvaccinecampaigninDistrictA)exceptthistime,censormedia.Advancetotheendofthesimulation.Thisiswhatyoushouldseeonyourscreen.
Noticethatthecurvesarefatherapartwhenwecensor.Whyisthisthecase?BesuretoexplainhowtheinfectedpopulationcurvesANDthevaccinecoveragecurveschange.Besuretoexplainwhythisalsomakessense.Thereismorespaceinbetweentheinfectedpopulationcurveswhenwecensorthemediaasopposedtowhenwedonot.Thismakessensebecausewhenwecensorthemedia,wearecuttingDistrictBofffromwhatishappeninginDistrictA.BecausetheyareunawareofthebotchedmeaslescampaigninDistrictA,theywillnotbeasopposedtoreceivingvaccinationsandsowewillnotseeaslargeofapeakintheinfectedchildrencurve.Asforthevaccinecoveragecurve,whenwecensorthemedia,againDistrictBunawareofwhatishappeninginSouthSudan.Assuch,thecoverageinDistrictBwillbehigherthanitisinDistrictAbecausethenewsofthebotchedmeaslescampaignisnotreachingDistrictBsotheywillnotexperienceachangeinthevaccinationcoverage.TheDistrictAcoveragethough,willfall.Becauseofthischange,weseeagapbetweenthetwocurves.4.Resetthesimulation.Nowincreasetheseveritytotherightmostsidesetting,mostsevere.Thecommunicationshouldbesetto0forbothdistricts.Censorthemedia.Advancethesimulationtotheend.Youshouldseethefollowingonyourscreen.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
5.Resetthesimulation.Nowkeepthesettingsthesameasaboveexceptdonotcensorthemedia.Thisiswhatyoushouldseeonyourscreen.
ComparethetwosetsofcurveswhentheseverityofthebotchedvaccinesinDistrictAisthemostsevere.Howdoestheseverityofthebotchedmeaslescampaignaffectthedistancebetweenthecurves?Thegapsagain,existbetweenthesecurvesisbecauseofcensoring.Therationaleisthesameasthepreviousquestion.Asthebotchedmeaslescampaignbecomesmoresevere,thedisparitybetweenthecoverageinDistrictAandDistrictBislessened.Thismakessensebecausewhilethecensoringislimitedtothemedia,migrantsforexamplearemovingintoDistrictBandthereisstillinformationspreading.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
6.Nowincreaseordecreasethecommunication&chancethecensorsettingsasyouadvancethroughdifferentsimulations.Whatdoyounotice?• Ifthemediaiscensored:
o Buyingpositiveinfluenceonlyfurtherbooststhecoverageo Negativeinfluencewilldecreasecoverageindependentlyofthebotched
measlescampaigninSouthSudan• Ifthemediaisnotcensored:
o BuyingpositiveinfluencewillhelpboostcoverageafterithasbeenaffectedbythenewsinSouthSudan
o NegativeinfluencewillfurtherbringthecoveragedownFinalQuestionsandThoughts:Iscensoringthemediaworthwhile?Doesithaveagreateffect?Instructor’sNote:Helptheparticipantthinkaboutthecostvs.thebenefitofcensoringthemedia.Asktheparticipant:whatmatters?Inotherwords,howinfluentialisthemediainUganda?Isthatthebestwaytocombatnegativeinformationsurroundingvaccinations?AccordingtothesimulationshowcanweachievethegreatestcoveragewhenthebotchedmeaslescampaigninDistrictAisverysevere?Ifyouhaveunlimitedresources?Ifyouhavelimitedresources?ThissimulationshowsthatweneedtocutoffthemediabecauseotherwisethebadnewswillspooktheUgandansandaffectcoverage.Withlimitedresources,youcanonlyaffectthepositiveinfluencetoalimitedcapacitywhereaswithunlimitedresourcesyoucaninsensepurchaseacceptabilityorratherpurchasepeople’swillingnesstoacceptandutilizethevaccine.HowdoyouthinkthoseinDistrictBwouldreactiftheylearnedthatthemediawascensored?Instructor’sNote:Haveparticipantstalkaboutthissotheycanlearndifferingperspectivesregardingcensoring.7.NowclickNextPageandproceedtothenextsimulation.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
SIMULATION4:PhilipsonintheDistricts1.Afterclickingthenextpagebutton,thisiswhatyoushouldseeonyourscreen.
2.Clicktheresetbutton.SelectPhilipson.Advancetotheendofthesimulation.Thisiswhatyoushouldseeonthescreen.
Popquiz:DescribethePhilipsoneffectinyourownwords.ThePhilipsoneffectispresentwhenparents’likelihoodofgettingtheirchildrenvaccinatedisdirectlyproportionaltotheprevalenceofthediseaseitself.WithoutthePhillipsoneffect,theparents’willingnessisnotbasedontheprevalenceofthedisease,butrathertheunderstandingthatreceivingavaccineisapositivesocialgood.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
3.Resetthesimulation.ClickNoPhillipson.Advancethesimulationtotheend.Thisiswhatyoushouldseeonthescreen.
DescribethedifferencesthatyouseeinvaccinecoverageasyouturnthePhilipsoneffectonandoff.WhenconsideringthePhilipsoneffect,thecoveragecurvesmoveinunisonwiththeinfectedcurves.Themorekidsthatareinfected,themorecoveragewewillsee.WhenthereisnotPhilipsoneffectweseethattheinfectedpopulationisnotthesoledriverofvaccinecoverage.4.Playaroundwiththissimulationandadjustthebotchedvaccineseverityandthecommunicationlevels.Describewhatyousee?Userswillseethatevenwhenbuyingpositiveinfluenceornegativeinfluence,underthepresenceofthePhilipsoneffect,thecoverageisnotinfluencedbytheacceptabilityortheparents’willingnesstovaccinatetheirchildren.Whatareyourfinalconclusions?Whatwouldyouliketoseemovingforward?Usethisspacetodiscussanynewand/orfinalthoughtyouhave.
Copyright 2018, The Johns Hopkins University and Teaching Vaccine Economics Everywhere.
WorksCited1. Weisstein,E.W.SIRModel.Availablefrom:
http://mathworld.wolfram.com/SIRModel.html.2. Geoffard,P.-Y.andT.Philipson,DiseaseEradication:PrivateversusPublic
Vaccination.TheAmericanEconomicReview,1997.87(1):p.222-230.