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Vaccine
jou rn al h om ep a g e :w w w . e l s e v i e r . c o m / l o c a t e / v a c c i n e
Effectiveness
of
rotavirus
vaccine
against
hospitalized
rotavirus
diarrhea:
A
case–control
study
Maria
Y.T.
Ichihara
a,∗,
Laura
C.
Rodrigues
b,
Carlos
A.S.
Teles
Santos
c,
Maria
da
Gloria
L.C.
Teixeira
a,
Sandra
R.
De
Jesus
d,
Sheila
M.
Alvim
De
Matos
a,
Jose
P.
Gagliardi
Leite
e,
Mauricio
L.
Barreto
aaInstituteofCollectiveHealth,FederalUniversityofBahia,RuaBasíliodaGama,s/n,CampusUniversitáriodoCanela,CEP40110-040,Salvador,Bahia,
Brazil
bDepartmentofInfectiousDiseaseEpidemiology,LondonSchoolofHygieneandTropicalMedicine,KeppelStreet,WC1H7HTLondon,UnitedKingdom
cDepartmentofExactSciences,UniversityoftheStateofFeiradeSantana,AvenidaTransnordestina,NovoHorizonte,CEP44036-900,FeiradeSantana,
Bahia,Brazil
dInstituteMultidisciplinarofHealth,CampusAnísioTeixeira,FederalUniversityofBahia,VitoriadaConquista,Bahia,Brazil
eAvenidaBrasil,4365-Pav.Hélio&PeggyPereira,CEP21040-360,RiodeJaneiro,Manguinhos,Brazil
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received20September2013
Receivedinrevisedform
13December2013
Accepted2January2014
Availableonline5February2014
Keywords:
Rotavirusdiarrhea
Vaccineeffectiveness
Acutediarrheahospitalization
Childdiarrhea
Vaccine Hospitalization
a
b
s
t
r
a
c
t
Rotavirusisoneoftheleadingcauseofhospitalizationandoutpatientsvisitsamongchildrenunder fiveyears.Thisstudyevaluatedoverallandgenotype-specificvaccineeffectivenessoforalmonovalent rotavirusvaccine(G1P[8]strain)inpreventinghospitaladmissionofBrazilianchildrenwithrotavirus acutediarrhea.
Ahospitalbasedcase–controlstudywasconductedinfiveRegionsofBrazilusingtheNationalRotavirus AcuteDiarrheaSurveillanceSystemfromJuly2008toAugust2011.Atotalof215cases(aged4–24 months)admittedwithconfirmedrotavirusdiarrheawererecruitedand1961controlshospitalized withoutdiarrheawerefrequencymatchedbysexandagegrouptocases.
Two-doseadjustedvaccineeffectiveness(adjustedbyyearofbirthandthefrequencymatching vari-ables)was76%(95%CI:58–86)lastingfortwoyears.Effectivenesscontrolledbytheavailablepotential confounderswas72%(95%CI:44–85),suggestingnoappreciableconfoundingbythosefactorsforwhich adjustmentwasmade.InahalfofthecasestherotavirusgenotypewasG2P[4]andin15%G1P[8]. Genotype-specificVE(twodoses)was89%(95%CI:78–95),forG1P[8]and76%(95%CI:64–84)forG2P[4]. ForallG1,itwas74%(95%CI:35–90),forallG2,76%(95%CI:63–84),andforallnonG1/G2genotypes, 63%(95%CI:−27–99).Effectivenessforonedosewas62%(95%CI:39–97).
Effectiveness of two-dose monovalent rotavirus vaccine in preventing hospital admission with rotavirusdiarrheawashigh,lastedfortwoyearsanditwassimilaragainstbothG1P[8]andG2P[4].Based onthefindingsofthestudywerecommendthecontinueduseofrotavirusintheBrazilianNational Immu-nizationProgramandthemonitoringoftheearlyemergenceofunusualandnovelrotavirusgenotypes.
©2014TheAuthors.PublishedbyElsevierLtd.
∗ Correspondingauthorat:RuaBasíliodaGama,s/n,4◦.Andar,Campus
Univer-sitáriodoCanela,Canela–CEP40110-040,Salvador,Bahia,Brazil.
Tel.:+557132837445;fax:+557133360695;mobile:+557188453456.
E-mailaddresses:my.ichihara@gmail.com(M.Y.T.Ichihara),
laura.rodrigues@lshtm.ac.uk(L.C.Rodrigues),carlosateles@yahoo.com.br
(C.A.S.TelesSantos),magloria@ufba.br(M.d.G.L.C.Teixeira),sandrego@hotmail.com
(S.R.DeJesus),sheilaalvim@hotmail.com(S.M.AlvimDeMatos),
jpgleite@gmail.com(J.P.GagliardiLeite),mauricio@ufba.br(M.L.Barreto).
1. Introduction
Acutediarrhea(AD)isafrequentcauseofchildhospitalization andoutpatientvisitsinchildrenunder5years[1].InBrazil,before introductionoftherotavirusvaccinein2006,about120.000 hos-pitalizationsayearoccurredduetoADinchildrenunderfiveyears (DATASUS/MinistryofHealthofBrazil,2006).
Rotavirusistheleadingcauseofsevereacutediarrheain chil-drenindevelopedandindevelopingcountriesandisthemajor causeofdeathinpoorcountries[2,3].Sevengroupsofrotavirus havebeenidentified(AtoG)andgroupA(RV-A)isresponsiblefor morethan90%ofhumanrotavirusinfections[4].RV-Ahasgreat geneticdiversityduealmost60serotypes(GandP)andthemost
0264-410X©2014TheAuthors.PublishedbyElsevierLtd.
http://dx.doi.org/10.1016/j.vaccine.2014.01.007
Open access under CC BY-NC-SA license.
commonstrainsare:G1P[8],G2P[4],G3P[8],G4P[8]andG9P[8][5]. InBrazil,between12%and42%ofchildrenunder5yearswith diar-rheahadpositivestoolsamplesforRV-Abeforetheintroduction oftheRV-Avaccine.Thisincreasedfrom22%to38%inchildren hospitalizedfor AD[6,7]. Morethan 51 genotypecombinations werereportedandthemostcommongenotypesdescribedwere G1P[8],G9P[8]andG2P[4][8].
Vaccinationisthebettermeasuretopreventrotavirus[1,2,9] anditsadoptionhasbeenrecommendedbyWorldHealth Organi-zation[10].AnattenuatedmonovalenthumanRV-A(G1P[8]strain; Rotarix®)andapentavalentbovine-humanreassortant(G1,G2,G3, G4andP[8]strains;RotaTeq®)arelicensedworldwide.Rotarix® wasintroducedintheBrazilianNationalImmunizationProgram (BNIP)in2006inatwo-dosescheduleat2and4monthsofageand co-administered withtetravalent, pneumococcaland poliovirus vaccines.
RV-AvaccineefficacyagainstsevereRV-AADvariedbetween morethan90%EuropeandAsia,85%inLatinAmerica,72%inSouth Africato49%inMalawi[11–14].Threecase–controlstudies car-riedoutinahighincomecountry(Belgium)[15]and inlowto middle-incomecountries(ElSalvadorandBolivia)[16,17]founda two-dosevaccineeffectivenessof90%;76%and77%respectively and a one-doseeffectiveness of91%; 51%and 56% respectively againsthospitalizationbyRV-AAD.InBrazil,twosmallcase con-trolsstudiesshowedarangeof40–85%effectivenessinpreventing hospitalization caused by G2P[4] [18,19]. Thereason for varia-tion in vaccineprotection is not clearand has beenattributed toantigendiversity,malnutritionand higherincidenceofother entericpathogens[20].Thereisstrongsuggestionofcross protec-tionamonggenotypes[11–14].
TheintroductionofRV-Avaccinationwasfollowedbya reduc-tioninchildhospitalizationdue toallcausesofADinBrazil,El SalvadorandMexicorangingfrom17to51%[21–23]anda reduc-tioninmortalityfromADinchildrenunder5yearsinBrazilof22% andinMexicoof41%[24].
Thisstudywill evaluatetheoveralleffectiveness of theoral monovalentvaccine,usedinroutinehealthservices,inpreventing BrazilianchildhospitalizationwithRV-AAD.Itwillalsoevaluate overallandgenotype-specificVEbytimesinceseconddose vacci-nation(uptotwoyears),andgenotype-specificVE.
2. Methods 2.1. Studydesign
This was a hospital based case–control study, frequency-matchedbysexandagegroup.Hospitalsweregeneralhospitals whichreceivedchildrenwithalargerangeofdiseasescomingfrom asimilargeographicalcatchmentarea.Seventeenofthehospitals enrolledintheRV-AADNationalSurveillanceSystemwereinvited toparticipateinthestudy,basedonhavinghadalargenumberof RV-Apositivesamplesin2007,adequateleveloforganizationof theunitanddataaccessibility.Afterconsultationandagreement onlogisticalarrangementswiththeFederalHealthSurveillance (SVS/MS),theepidemiologicalsurveillanceofthehospitalsandof thestates,theCentralPublicHealthandNationalReference Labo-ratories,10hospitalslocatedinfivemacro-regionsofBrazil(6state capitalcitiesand4municipalities)wereselected.
3. Participants 3.1. Eligiblechildren
Childrenwereeligibletoparticipateinthestudyiftheywere admitted in the study hospitals, were aged 4 to 24 months (andthereforeoldenoughtohavereceivedtheirseconddoseof rotavirusvaccine)and didnothave diarrheauptothreeweeks beforeadmissionor duringhospitalization. Alleligible children
werelistedandscreenedtoexcludechildrenwhohadanyhealth conditionpresumedtoreducevaccineeffectiveness (immunodefi-ciency,gastrointestinaldisease(e.g.diverticulitis),malformations orneoplasmconditionsrelatedtovaccineeffectiveness,general signsandsymptoms,infectiousandparasiticdiseases),thosewho hadreceivedtheseconddoseofvaccineinthe15daysbefore hospi-talization,orwhosevaccinationdidnotfollowtheBNIPschedule. Allthatfulfilledthespecificcriteriaforeithereffective’scaseor controlwereincluded.Thisaimedtoselectcontrolsfromthe pop-ulationthatproducedthecases,ascaseshospitalizedbyADorby otherdiseaseswerelikelytocomefromthesamepopulationgiven theuniversalhealthcaresysteminBrazil.
3.2. Potentialcasesandcontrols
Inclusioncriteriaforpotentialcaseswere:admissionwithAD (definedasthreeormoreliquidstoolsin24h,upto14daysbefore admission),stoolsamplewascollecteduntil48hafteradmission andpositiveforRV-Aandstayinhospitalforatleast24h.Children wereincludedinthestudyinthefirsthospitalizationonlyandhad noassociatedisease.
Inclusioncriteriaforcontrolswere:admissionfromthesame hospitals of the cases with respiratory, genitourinary, muscu-loskeletal,nervoussystems,skinandsubcutaneoustissue,earand mastoidprocesses,eyeandadnexadiseases,andexternalcauses. Controlswerenotincludediftheyhadaprevioushistoryof RV-Adiarrheaorhadavaccine-preventabledisease(aschildrenwho didnotreceiveonevaccinearemorelikelytonotreceiveother vaccines).
Allpotentialcontrolsfulfillingthecriteriaaboveundergonea furtherselectionforfrequencymatching,sothatthealleffective controlshadthesamedistributionofthemainconfounding vari-ables(sexandagegrouponadmission:4–6months;7–11months and12–24months)asthecases.Thisapproachaimedtoselectfrom thepoolofpotentialcontrols,aneffectivecontrolgroupwiththe samedistributionofconfoundersastheeffectivecases;inthe sit-uationinwhichmorecontrolsthanneededwereavailableinthe frequencymatchedgroupstheywereselectedatrandom.Random selectionoffrequencymatchedeffectivecontrolsfromthepoolof potentialcontrolswasdoneusingthe“sample”commandofthe Stataversion11.0
3.3. Effectivecasesandcontrols
Cases:Allpotentialcasesfulfillingthecriteriaaboveandhad stoolspositiveforrotavirusconfirmedbythereferencelaboratory wereincluded.
Controls:Allpotentialcontrolsfulfillingthecriteriaaboveand randomselectedforfrequencymatchingwereincluded.
Onestoolsamplewascollectedupto48hafteradmissionas partof theRV-A AD SurveillanceSystem.Samples werestored andtransportedtotheLACENsofeachStatewherethehospital waslocated,accordingtotheguidelinesof theGeneral Coordi-nationofPublicHealthLaboratories/MinistryofHealthofBrazil (CGLAB/SVS/MS).RV-AinvestigationwasdonebyEnzymeImmune Assay(EIA),usingcommercialkits,followingthemanufacture’ rec-ommendation(Dako®orOxoide®).
3.4. Laboratoryinvestigationofpotentialcases
AllpositivesamplesforRV-Aand25%ofnegativesampleswere senttoareferencelaboratory.AccordingtotheLACEN localiza-tion,thiswaseithertheNationalReferenceLaboratory(Evandro ChagasInstitute[Belém,PA],oraRegionalReferenceLaboratory (AdolfoLutzInstitute[SãoPaulo,SP],andOswaldoCruzInstitute [RiodeJaneiro,RJ]).ResultswereconfirmedbyEIAand polyac-rylamidegelelectrophoresis(PAGE)accordingtoLeiteetal.[25].
Fecalsuspensionsand nucleicacidsextractionwerecarried out accordingtoLeiteet al.[25] andBoom etal.[26],respectively. TheRV-GenotypingwasconductedusingRT-PCRasdescribedby Dasetal.[27](“G”genotype)andGentschetal.[28](“P” geno-types).RV-Agenotypesweree-mailedtoCGLAB/SVS/MSandsent totheInstituteofCollectiveHealth, FederalUniversityofBahia (ISC/UFBa).
4. Datacollection
Informationfromcasesandcontrolswascollectedby interview-erswhovisitedallhospitalsdaily,fromJuly2008toAugust2011. Medicalrecordswerereviewedandthechild’scareranswereda standardquestionnaireonidentification,clinicalhistoryand evo-lution,socio-economicstatus,sanitation,feedingandnutritional statusofthechild,andmaternalreproductiveaspects.The vac-cinationstatusofthechildwasassessedthroughthevaccination card,askedforduringhospitalization.Also,datawereobtainedby homevisits,telephoneorthefamilyhealthteamoftheareaof resi-denceofthechild.Vaccinationstatuswasclassifiedaccordingtothe presenceandnumberofdosesandtimebetweenlastdoseand hos-pitalization.Weightatadmissionwastakenfromhospitalrecords anditsdeficitevaluatedaccordingtotheweight-agestandardsof theNationalCentreforHealthStatistics(NCHS)forboysandgirls [29].Mother’sskincolorwasselfreported.
Questionnairesforallpotentialcasesandcontrolsweresentto ISC/UFBaandreviewersconfirmedtheclassificationofcasesand controlsbyassessingtheinclusionandexclusioncriteria.
Tocomplementdataonmaternalreproductiveperiodandchild birthweconsultedlivebirthsroutinedata(SINASC)from7cities. Thissystemcovers80–90%of birthsinBrazil.Thechildageon admissionandonadministration offirst and seconddoses and breastfeedingdurationwerecalculatedindaysatthedateof admis-sion. Casesand controls were classifiedinto three age-groups, accordingtoage onadmission:4–6months, 7–11months and 12–24months.
5. Samplesize
Theminimumsamplesizerequired(usingEPI-INFO6.0)was88 casesand88controls(forvaccinecoverageof70%,VEof65%,95% confidenceintervaland90%power.Theachievedsamplesizeof215 casesand1961controlsenabledestimationofgenotype-specific vaccineeffectiveness.
6. Statisticalanalysis
Vaccineeffectivenesswasobtainedbymultivariable uncondi-tionallogistic regression, which is appropriate when frequency matching is used. Theodds ratio wasadjusted for: a) sex and agebothusedforfrequency-matching,b)yearofbirth,tocontrol coverageofvaccinebyyearandc)robustvarianceestimationof Jackknife,withclustersbeinghospitals.Potentialconfounderswere includedinthefinallogisticmodelwhenthep-valueof associa-tionwas<0.20(bivariateanalysis).Weusedthebackwardmethod toanalyzethepresenceofconfounding.Thebestadjustmentwas givenby theAkaikeinformation criterion (AIC) [30].Given the absenceof confoundingby measuredvariables apparentin the analysisbynumberofdoses,thesubsequentanalysisbytimesince seconddosevaccination,genotype-specificwasconducted with-outcontrollingforconfoundersotherthanage,sex,yearofbirth, androbustvarianceestimationofJackknife.Thefrequencyof miss-ingvaluesforanyconfoundingvariablewasverylow(lessthan 1%),andtheywereattributedtothecategoryofreference (consid-erednotexposed)tokeepallcasesintheanalysis.Werepeatedthe
analysisstratifiedbyyearofadmissiontocontrolforincreasing vac-cinecoveragewithtime.Asensitivityanalysis(fortwodosesonly) wasdone,inwhichcasesandcontrolswithmissingvaccination cardsweretreatedasvaccinatedorunvaccinated,soassumingnon differentialmissingness.TheVEwascalculatedbythefollowing formula:VE=(1−oddsratioofvaccination)×100.Statistical anal-ysiswasperformedwithStataversion12.1(Copyright1985–2011 StataCorp).
Ethics:ThisstudywasapprovedbytheCommitteeofISC/UFBa (Protocol017-08/CEP/ISC-2008).Carersof participatingchildren signedawritteninformedconsentform.
7. Results
7.1. Studypopulation
Atotalof4955eligiblechildrenagedbetween4and24months wererecruitedintothestudyfromJuly2008toAugust2011.Of these,697childrendidnotfulfillthecriteriaofinclusionrelatedto informationonvaccination:268didnothaveavaccinecard;299 hadreceivedvaccinationinadifferentschedulefromthat recom-mendedbytheBNIP;and130hadreceivedtheseconddosefewer than15days beforeadmission. (Fig.1showsthebreakdownof exclusionsforeffectivecasesandcontrols).Inaddition,298 eligi-blechildrenwithADdidnotfulfillthecriteriaofinclusionrelatedto thestoolsamplecollection:in202astoolsamplewasnotcollected; in33thesampleswerelost,andin63thesamplewascollectedtoo longafteradmission.Samplesof965potentialcasesweretested forRV-Awiththefollowingresults:722werenegative(ofwhich 142hadanothervirusidentifiedand28werepositiveonthefirst testbutnegativeinthereferencelaboratory)and215werepositive forRV-AconfirmedbyEIAand/orPAGEandRT-PCR.Ofalleligible childrenforcontrols,191haddevelopeddiarrheaduring hospital-izationandwerenotselectedtothestudyand843werenotneeded giventhefrequencymatch.Atotalof215effectivecasesand1961 effectivecontrolswererecruited.
Characteristics of thestudy populationare presented inthe Supplementarytables(1a,1b,1c).Themeanageofthecasesand controlswas14months.Comparedtocontrols,caseshadlower socio-economicstatusandsanitarylevel,theirmothershadfewer yearsofschoolingandtheirfamilieslivedinsmallerhouseswith manyfamily membersand more thanonechild under5 years. Smokingandalcoholconsumptionduringpregnancyanddelayed startofprenatalcareweresignificantlyhigheramongcases.Also, oneormorevisitstohealthservicesorhospitalizationsdueto diar-rheabeforethecurrentadmissionweremorefrequentincasesthan controls.Therewasahigherproportionofcontrolswhowerenever exclusivelybreastfed(12.1%)comparedwithcases(7.4%).
Theuseofvaccinebetweencasesandcontrolswassignificantly different:31.2% (67)cases werenot vaccinated compared with 10.3%(201)ofcontrols,whereas53.5%(115)ofthecasesand75.5% (1481)ofthecontrolshadreceivedtwodosesofvaccine.
OfthechildrenuptotwoyearsadmittedtohospitalwithAD, 22.3%wereRV-Apositiveand156(73%)weregenotyped.The dis-tributionof RV-AGand Pgenotypes ispresented inFig.2 and SupplementaryTable2GandPgenotypeswereidentifiedin135 (63.3%)ofallRV-Apositivesamples(n=215),andonly“G”or“P” typesin 21samples.Therewasapredominanceof theG2P[4] genotype(51.3%,n=80)followedbyG1P[8](15.4%,n=24).Ofall observedgenotypes,G2wasfoundin57%(n=89)andG1in23% (n=36).The othergenotypescharacterizedwere: mixedgroups (n=14),G9(n=6),G3(n=3),andunusualstrainssuchasG12(n=2) andGroupC(n=1).Mixedinfectionsandunusualgenotypeswere identifiedin10.9%oftheRV-Apositivesamples.
Fig.1.Studypopulation.
Fig.2.GenotypescirculatinginBrazilfrom2008to2011.
8. Vaccineeffectiveness
Thetwo-doseadjustedVE(adjustedforyearofbirthandthe frequencymatchingvariables)was76%(95%CI:58–86)(Table1).
Effectiveness controlled by the available potential confounders was very similar (72%, 95%CI: 44–85), suggesting no apprecia-ble confounding by those factors for which adjustment was made.
Table1
EffectivenessoforalmonovalentrotavirusvaccineinpreventinghospitaladmissioninBrazilianchildrenwithrotavirusacutediarrheabynumberofdosesreceived.
Vaccinationby Case Control ORa VEa ORadjb VEb
Numberofdoses n n (95%CI) (95%CI) (95%CI) (95%CI)
Unvaccinated 67 201 1 – 1 –
Fullyvaccinated(twodoses) 115 1481 0.24(0.14–0.42) 76(58–86) 0.28(0.15–0.56) 72(44–85)
Partiallyvaccinated(onedose) 33 279 0.38(0.23–0.61) 62(39–77) 0.40(0.25–0.63) 60(37–75)
AICc 1318.253 1194.454
aOddsratioadjustedbyyearofbirthandvariables(sexandagegroup)usedforfrequencymatching,androbustvarianceestimationofJaccknife,wheretheclusterswere
thehospitals.Thevaccineeffectiveness(VE)wascalculatedby(1−OR)×100%.
b Oddsratioadjustedbyyearofbirthandvariables(sexandagegroup)offrequencymatchingandconfounders(mother’sschooling,mother’sabsencefromhome,smoking
duringpregnancy,typeandregularityofwatersupply,numberofADhospitalizationsbeforecurrentadmissionandexclusivebreastfeeding)androbustvarianceestimation
ofJaccknife,wheretheclusterswerethehospitals.cAkaikeinformationcriteriaformeasuringthegoodnessoffitofthestatisticmodel.
Weexcludedasimilarproportionofcases(5.7%)andcontrols (5.3%)becausetheydidnothavecards.Sensitivityanalysisshowed thatiftheywereincludedasvaccinated,VE(twodoses)wouldbe 66%(95%CI:42–80)andifincludedasunvaccinatedVEwouldbe 74%(95%CI:53–86).
TheVE(adjustedforyearofbirthandthefrequencymatching variables)foronedosewas62%(95%CI:39–97)andonedoseVE adjustedforotherpotentialconfounderswas60%(95%CI:37–75). Table2showsthatVEwassimilarinthosewithtimesince sec-onddosevaccinationuntilhospitalization stratifiedbyoneyear (71%;95%CI:54–82)andtwoyears(78%;95%CI:52–90).TheVE forG1P[8]andG2P[4]bytimesinceseconddosevaccinationwas marginallyhigherforG1P[8](90%;95%CI:-0.92–-100foroneyear and89%;95%CI:0.01–-99fortwoyears)thanG2P[4](77%;95%CI: 57–88foroneyearand75%;95%CI:56–86fortwoyears)significant. Table3presentsgenotype-specificVEbynumberofdoses.VE (twodoses)was89%(95%CI:78–95)forG1P[8];76%(95%CI:64–84) forG2P[4];74%(95%CI:35–90)forallG1;76%(95%CI:63–84)for allG2and63%(95%IC:−27–99)forallthenonG1/G2genotypes.
EstimatedVEremainedverysimilarwhenanalysiswas strati-fiedbyyearofadmissionsuggestingthatVEdidnotchangewith increasingvaccinecoverage(datanotpresented).
9. Discussion
Two-doseVEwas76%(95%CI:44–85),inspiteofthegreat diver-sityofrotavirusgenotypescirculatinginBrazilandapredominance ofG2P[4]genotype(51.3%).Wefounda10.9%mixedandunusual genotypesas expected in developing countries[31,32]. The VE
lastedfortwoyearsafterseconddosevaccinationanditwashigher forG1P[8]thanG2P[4].
VariationofRV-Avaccineefficacyandeffectivenesshavebeen reportedintheliterature: efficacywashigherinEurope(96.4% againstRV-AsevereAD)[11]thaninalowincomecountry(Malawi, 49.2%againstalldiarrheaand57.5%againsthospitalizeddiarrhea) [13]andincountrieswithhighmortality(63%)[33].Inthemiddle incomecountriesofLatinAmerica[12],efficacywas84.8%against severeAD;inSouthAfricaitwas72.2%againstalldiarrhea[13].This studyshowedsimilareffectivenesstothatfoundinElSalvador[16] andBolivia[17](73%and76%forseverediarrhea)andinasmaller studyinBrazil[18](75.8%againsthospitalizeddiarrhea),butlower thaninBelgium(90%)[15].
Two-doseVEremainedhighfortwoyears.Thisissimilartoother countrieswithlowmortality;butdifferentfromsomecountries withhighmortalitywhereVEdecreasesinthesecondyearafter vaccination[5].ArecentstudyinNicaraguaalsofoundno wan-ing for thepentavalent vaccinein children aged12 monthsor morewithverysevereAD[34].Otherreasonsforthefindingthat effectivenessdidnotdecreaseinthesecondyearinourstudyare: weexploredVEfromtimesinceseconddosevaccinewhilemost countriesestimatedVEbytimesincebirth;andweestimatedVE againstseverecasesonly.Besides,declinesobservedinother stud-iescouldberelatedtothesmallnumberstoestimateeffectiveness inthesecondyearoflife[35].Thereisnoagreementastothe rea-sonsforthevariationinVEandindurationofVEintheliterature. ThefactthateffectivenessinBrazilwassimilartoothermiddle incomecountriesintermsofoverallprotectionagainst hospital-izedADandsimilartoEuropeancountriesinrelationtowaning mighthelptoadvanceinthisexploration.
Table2
EffectivenessoforalmonovalentrotavirusvaccineinpreventinghospitaladmissioninBrazilianchildrenwithrotavirusacutediarrhea(overallandgenotype-specific)
stratifiedbytimefromreceivingtheseconddoseofvaccineuntilhospitaladmission.
Timesincethe Case Control ORa VEa
Seconddose n n (95%CI) (95%CI)
Overall Unvaccinated 67 201 1 – <1year 71 938 0.26(0.16–0.42) 74(58–84) 1to2years 44 543 0.22(0.10–0.46) 78(54–90) AICb(1114.384) G1P[8] Unvaccinated 9 201 1 – <1year 4 938 0.10(0.005–1.92) 90(-0.92–100) 1to2years 3 543 0.11(0.01–99) 89(0.01–99) AICb(168.4906) G2P[4] Unvaccinated 25 201 1 – <1year 22 938 0.23(0.12–0.43) 77(57–88) 1to2years 19 543 0.25(0.14–0.44) 75(56–86) AICb(533.5553)
aOddsRatioadjustedbyyearofbirthandvariables(sexandagegroup)usedforfrequencymatching,androbustvarianceestimationofJaccknife,wheretheclusterswere
thehospitals.Thevaccineeffectiveness(VE)wascalculatedby(1−OR)×100%.
Table3
Genotype-specificvaccineeffectivenessoforalmonovalentrotavirusvaccinebynumberofdosesreceived.
Vaccinationby Case Control ORa VEa
Rotavirusgenotype n n (95%CI) (95%CI)
G1P[8]
Unvaccinated 9 201 1 –
Fullyvaccinated(twodoses) 7 1481 0.11(0.05–0.22) 89(78–95)
Partiallyvaccinated(onedose) 8 279 0.69(0.30–1.57) 31(−57–70)
AICb(236.815)
G2P[4]
Unvaccinated 25 201 1 –
Fullyvaccinated(twodoses) 41 1481 0.24(0.16–0.36) 76(64–84)
Partiallyvaccinated(onedose) 14 279 0.43(0.22–0.85) 57(15–78)
AICb(641.170)
G1
Unvaccinated 10 201 1 –
Fullyvaccinated(twodoses) 18 1481 0.26(0.10–0.65) 74(35–90)
Partiallyvaccinated(onedose) 8 279 0.62(0.22–1.79) 38(−79–78)
AICb(350.510)
G2
Unvaccinated 29 201 1 –
Fullyvaccinated(twodoses) 50 1481 0.24(0.16–0.37) 76(63–84)
Partiallyvaccinated(onedose) 17 279 0.44(0.26–0.74) 56(26–74)
AICb(743.862)
NonG1/G2
Unvaccinated 3 201 1 –
Fullyvaccinated(twodoses) 6 1481 0.37(0.11–1.27) 63(−27–99)
Partiallyvaccinated(onedose) 2 279 0.47(0.72–3.09) 53(−2.09–28)
AICb(137.232)
aOddsratioadjustedbyyearofbirthandvariables(sexandagegroup)usedforfrequencymatching,androbustvarianceestimationofJaccknife,wheretheclusterswere
thehospitals.Thevaccineeffectiveness(VE)wascalculatedby(1−OR)×100%.
bAkaikeinformationcriteriaformeasuringthegoodnessoffitofthestatisticmodel.
Asingledoseofferedsomeprotection,consistentwiththe lit-erature(althoughtheVEwashigherthaninElSalvador[16]and Bolivia[17]andlowerthaninBelgium(91%))[15].
Thegoodeffectivenessidentifiedisconsistentwiththe reduc-tionintherateofchildhospitalizationandmortalitybyADinBrazil followingtheintroductionofvaccineinBrazil[21].
Genotype-specificVE washighforG1P[8] (89%)and slightly lower for G2P[4] (76%) indicating a degree of cross protec-tion.Animalmodelsshown thatimmunitytogroupArotavirus (RVA) present homotypic and heterotypic components. Repeat RVAinfectionsacquirednaturallyorbyvaccination,increase pro-tectiveimmunitytoincludemultipleserotypes,as indicatedby developmentofcross-neutralizingantibodiesandcross-reactive epitope-blockingantibodiesspecificforVP7andVP4antigens.In thehumanvaccineclinicaltrials (monovalent,Rotarix®; penta-valent,RotaTeq®)aswellasinthefollow-upstudies,bothvaccines presented homotypic as well as heterotypic protection against differentRVAgenotypes,includingG2P[4]andG9P[8]genotypes [12,19,36,37].
GenotypespecificVEalsoremainedhighinthesecondyear,in contrastwiththefindingsformiddleincomecountries.VEwas74% forallG1types,76%forallG2typesandlowerforthenonG1/G2 type(63%),althoughnumbersweresmall.TheresultofVEagainst G2P[4]issimilartothetwosmallstudiescarriedoutinBrazil(75.4% to77%toG2P[4])butunlikethem,effectivenessagainstbothG1P[8] andG2P[4]didnotfallinthesecondyear[18,19].
Thereisadiscussionastowhethervaccineuseleadstoserotype replacement[19].ThehigheffectivenessagainstbothG1P[8]and G2P[4]suggeststhatthepredominanceofG2P[4]ismostlikelya cyclicalpatternofrotavirusstrainsoccurrenceinBrazilas previ-ouslyreported[38,39].
Thisstudyavoidedthepossibilityofartificiallyreducing effec-tivenessbyusingcontrolswithoutdiarrhearatherthancontrols withdiarrheaand(potentialfalse)norotavirusinstool.UsingEIA, PAGEandRT-PCRweconfirmedthatallcasesweretruecasesof RV-A.
Thedatacollectionstrategyallowedustoobtainindividualdata, tocontrolforpossibleconfoundingandverifyinteractionsin over-allVE.Aftercontrollingforsevenvariables,noconfoundingwas identified.
Wewereunabletoinvestigateeitherifeffectivenessdeclines aftertwoyearsofseconddosevaccineorwhetherthereisan inter-actionwithoralpoliovirusvaccineasthetwovaccinesaregiven atthesametime.Weassumednondifferentialmissingnessinthe sensitivityanalysis.Althoughthiswasacasecontrolstudyrecall biasisnotrelevantbecausewedidnotrelyonrecallof vaccina-tion;weusedarecord(vaccinecard)forestablishmentofthemain exposure.
Only73%ofgenotypesoftheRV-Apositivesamplewere iden-tified.Thiscouldhidethecirculationofothergenotypes,although, wewereabletoestimategenotype-specificVEforthemost com-moncirculatingstrains.
Inconclusion,weshowedconsistenteffectivenessoftwo-dose oral monovalent vaccine in preventing hospital admissions of BrazilianchildrenwithRV-AAD,closertoEuropeanthanAfricaVE. ProtectionlastedfortwoyearsanditwassimilaragainstG1P[8]and G2P[4]andslightlyloweragainstnonG1/G2.Thefirstdosealready conferredsomeprotection.
Thefindingsofthestudysupportsthecontinueduseofrotavirus intheBrazilianNationalImmunizationProgramandthe monitor-ingforearlydetectionofemergenceofunusualandnovelrotavirus genotypes.
Sincethis vaccine(whichrequires onlytwodosesandis co-administeredwithothervaccines)providesadequateprotection, thebenefitsofachangetoamultivalentvaccinerequiringthree dosesmightarequestionable:thismaynotincreaseprotectionand leadtoincompletevaccinationschemes.
It might be useful to conduct cost-effectiveness stud-ies to inform national immunization policy. In addition, other effectiveness studies should investigate what is behind the observed variation in monovalent rotavirus vaccine VE.
Finally,itisimportanttoidentifyearlyemergenceofunusual andnovelrotavirusgenotypessothatthevaccineeffectivenesscan beverified.
Conflictofintereststatement
Allauthorsconfirmthattherearenoknownconflictsofinterest associatedwiththispublicationandtherehasbeennosignificant financialsupportforthisworkthatcouldinfluenceitsoutcome. Contributors
MYTIdesignedthestudy,managedthefieldwork,analyzedand interpretedthedataandwrotethepaper.LCRcontributedtothe analysisandtheinterpretationofthedataandwroteup.CASTS contributedtoanalysisandinterpretationofthedata;MdaGLCT contributedtointerpretationofthedata;SRdidtheinitial analy-sisofthedata;SMAMcontributedtopreparethedatatoanalysis; JPGLcontributedwiththedesignofthestudyandinterpretation ofthedata;MLBcontributedwiththedesignofthestudy, analy-sisandinterpretationofthedata.Alltheauthorscontributedto editthepaper.Themanuscript hasbeenread and approvedby allnamedauthorsandthattherearenootherpersonswho sat-isfiedthecriteriaforauthorshipbut arenotlisted.Theorderof authorslistedinthemanuscripthasbeenapprovedbyallofus. Allauthorshavegivendueconsiderationtotheprotectionof intel-lectualpropertyassociatedwiththisworkandthatthereareno impedimentstopublication,includingthetimingofpublication, withrespecttointellectualproperty.Insodoingtheauthors con-firmthattheyhavefollowedtheregulationsoftheirinstitutions concerningintellectualproperty.
Ethicalapproval
This study was approved by the Committee of Institute of Collective Health, Federal University of Bahia (Protocol 017-08/CEP/ISC-2008), by four local ethics committees. Consent to participatewasobtainedfromallthehospitals.Carersof partici-patingchildrensignedwrittenaninformedconsentform. Funding
ThisworkwassupportedbyHealthSurveillanceofMinistryof HealthofBrazilwhocollaboratedinrecruitmentofsitesbutno roleinstudydesign,incollection,analysis,interpretationofdata, inthewritingofthereportorinthedecisionofsubmitthearticle forpublication.
Acknowledgments
WerecognizethecontributionoftheROTAVACGroupwhich includesalltheprofessionalsenrolledintherotavirusAD Surveil-lanceSystem whoparticipated inthe conduction ofthe study: Alessandra Araújo Siqueira, GreiceMadeleine, Rejane Maria de SouzaAlves,VivianeMartins,MarliCosta,ErnaniRenoir,Eduardo doCarmoHage(HealthSurveillanceofMinistryofHealth,Brasilia, Brazil); Alexandre Madi Fialho, Rosane Santos Maria de Assis (RegionalReferenceLaboratory,FIOCRUZ,RiodeJaneiro,Brazil); RitaCássiaCompagnoliCarmona(RegionalReferenceLaboratory, AdolfoLutz,SaoPaulo,Brazil);JoanaD’ArcPereiraMascarenhas, LuanadaSilvaSoares(NationalReferenceLaboratory/Evandro Cha-gas,Belém,Brazil);AcáciaPerolina ResendeSetton,Adelaideda SilvaNascimento,AnaGabrieladeAndradeCarreira,ÂngelaMaria RodriguesFerreira,FabíulaMariadeAlmeidadeHolandaTormenta, JaneteXavierdosSantos,TeoníliaLoulaDourado,MaraEspíndola
CardosoAraújo,MarcoAureliodeOliveiraGoes,MariaElisaPaula deOliveira,MaríliaReicheltBarbosa,MariaCristinaToledoCoelho, SandraCristinaDeboni(ADSurveillanceSystemoftheStatesand Municipalities,Brazil);IvanaR.S.Varella,EleniceBrandãoCunha, EmersonHenklainFerruzz,MaríciadeMacedoMoryKuroki,Maria deFátimaRezendeDóriaPinto,MariaRoseildaB.BarretodaSilva, NiedjaMaria de OliveiraCosta MedeirosNetto,Sandra Mendes deMagalhãesdaSilva(TechniciansofCore Surveillanceof hos-pitals,Brazil);AnaAcáciaPereira,AuxiliadoraNovais,LinaMaria Matos,LeonardoBertollo,MariadoRosárioMachadoLisboaLuna, Raimunda Carvalho,Renilda BetoneMoura,BrenoBrito, Sandra MariaAraújoMenezesCavalcante(PublicHealthCentral Labora-toriesoftheStates).
AppendixA. Supplementarydata
Supplementary data associated with this article can be found,intheonlineversion,athttp://dx.doi.org/10.1016/j.vaccine. 2014.01.007.
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