COVID-19--Herd-Immunity-and-Convalescent-Plasma--T

Thisarticlehasbeenacceptedforpublicationandundergonefullpeerreviewbuthasnotbeenthroughthecopyediting,typesetting,paginationandproofreadingprocess,whichmayleadtodifferencesbetweenthisversionandtheVersionofRecord.Pleasecitethisarticleasdoi:10.1002/jmv.25870.Thisarticleisprotectedbycopyright.Allrightsreserved.AcceptedArticleKirtimaanSyalORCIDiD:0000-0002-0046-0205COVID-19:HerdImmunityandConvalescentPlasmaTransferTherapyKirtimaanSyal,PhD,PGDMLEScientist,ChemicalBiologyandTherapeutics,StJudeChildren’sResearchHospital,Memphis,TN,UnitedStatesofAmerica38105andDepartmentofBiochemistry,UniversityofWisconsin-Madison,WI,UnitedStatesofAmerica53706EmailID:[e-mail];Phone:[phone]Coronavirusdisease2019(COVID-19),causedbySevereAcuteRespiratorySyndromeCoronavirus2(SARS-CoV-2),hasspreadworldwidetriggeringapandemic.ItsfirstcasewasreportedinWuhan,thecapitalofChina'sHubeiprovince,andsincethenithasspreadacrossworldbecomingoneoftheworstpandemicsinthehistoryofmankind1.Itsbasicreproductivenumber(R0)hasbeendeterminedtobe2-32.Here,basicreproductivenumberistheaveragenumberofsecondarycasesgeneratedbyinfectedsubjectinthecompletelysusceptiblepopulation.Anypandemicwithbasicreproductivenumberlessthanonewilldieoutonitsown3.Togiveaperspectivetothisnumber,the1918-influenzapandemicwhichinfectedonethirdofworld’spopulationandresultedin50millioncasualtieshadreproductivenumberof1.84.MajorityofCOVID-19patientsshowmildsymptomsandrecoverontheirownintwotothreeweeks,soitislikelythatcasescouldgoundetectedandtheactualbasicreproductivenumberismuchhigherthanstatedabove.COVID-19Thisarticleisprotectedbycopyright.Allrightsreserved.AcceptedArticlesymptomsincludefever,cough,sorethroat,diarrhoea,shortnessofbreath,lossofsmell/taste,pneumoniaandinseverecases,itcanleadtomultipleorganfailureanddeath5.Theoverallrateofmortalityperconfirmedcaseshasbeenreportedtobenearly4.5percent6.Therateofrecoveryandseverityofthediseasedependontheageandhealthofthesubjects.Theyoungeragegroupwithoutanypre-healthconditionisexpectedtohavealowdeathrate(0.2percent)whereasolderpopulation(above80)havemuchhigherdeathrate(15percent)6.Researchisbeingcarriedoutforvalidatingtheavailablepotentialtreatmentregimeandvaccines,andfordevelopinganewone.HerdImmunityandplausiblestrategyagainstCOVID-19Herdimmunityisanage-oldconcept.Itisanindirectprotectionconferredbyimmuneindividualstothesusceptibleonesinagivenpopulationagainstaspecificpathogenicinfestation.Herdimmunityprotectsbylimitingthespreadofthedisease7.R0numberdeterminestheminimumpercentage(Y)ofpopulationrequiredtobeimmuneforachievingtheherdimmunityfortheentirepopulation7.Here,Y=(R0–1)/R0 X1007Asdescribedbefore,R0=2-3asperrecentreports.IfR0=2,thenY=[(2-1)/2]X100=50%Similarly,whenR0=3,thenY=[(3-1)/3*100=66.66%Therefore,forR0=2-3,nearly50to66.66percent*(threshold)ofthepopulationisrequiredtobeimmuneagainstCOVID-19fortheprotectionofsusceptibleindividualsinagivenpopulationthroughherdimmunity.*Asdiscussedpreviously,itcanbehigherascasesaremostlikelyunder-reported.Inemergencysituations,recoveredsubjectswhoarenegativeforCOVID-19canbeconsideredforvoluntarytemporaryemploymentatsensitivelocationssuchashospitalsandairportaspertheircapabilityandskillset.Suchlocationshavethepotentialtobecomethehotbedforspreadofinfections.Inpresenceofimmunevolunteerworkers,spreadofthediseasewouldberestricted.TherecoveredThisarticleisprotectedbycopyright.Allrightsreserved.AcceptedArticleindividualsifplacedinhighenoughnumberatsensitivelocationcanactasasourceofindirectimmunity8andprotectthetargetpopulation.Thecoronaviruscannotre-infecttherecoveredsubjects.ThoughfewreportsfromJapansuggestthepossibilityofreinfectionbutithasbeendisputedbysomeexpertswhobelievedthatredetectionwasduetotheerrorindiagnosisandnotthereinfection9.Somehealthofficialsalsoconsideredittobethecasesofre-activationoflatentCOVID-199.InChina,nearly14%patientscheckedfor14daysafterresolutionofallsymptoms,showedthepositiveRNAtest10.Thepossibilityofamutationandemergenceofanewstrainofaviruscannotberuledoutanditcanmakeherdimmunityineffective8.Onapositivenote,inductionofherdimmunitybyvaccinationisatriedandtestedapproach.Allplacesarenotequallypronetothespreadofinfectionespeciallyindevelopingcountries.LocalizedherdimmunitycanhelpinfurtherimpedingthespreadofCOVID-19.ConvalescentPlasmaCollectionOneoftheinvestigationaltreatmentbeingresearchedistheadministrationofconvalescentplasmacollectedfromrecoveredpatientstoCOVID-19patients.Here,convalescentplasmafromrecoveredpatients(orsurvivors)containneutralizingantibodiesagainstCOVID-19.MosteffectiveconvalescentplasmawithhightitreofneutralizingantibodiesasdeterminedbyELISAassaysshouldbestoredinbloodbanks.Previously,ithasbeenshownthatconvalescentplasmatransferfromrecoveredpatientstocriticalsubjectshelpedinrecoveringfromdreadfulinfectionssuchasEbolaandInfluenza11.InChina,ShenetalandDuanetalhaveshowedthatconvalescentplasmatherapycouldhelpinprognosisofseverecasesofCOVID-1912-13,andlargescaleclinicaltrialsarebeingconductedtovalidatetheirfindingsatseverallocationsinUnitedStates