欧洲疾控中心-流感嗜血杆菌病-2023年度流行病学报告 Haemophilus influenzae disease Annual Epidemiological Report for 2023

ECDC

Suggestedcitation:EuropeanCentreforDiseasePreventionandControl.AnnualEpidemiologicalReportfor2023-Haemophilus

influenzaedisease.Stockholm:ECDC;2025.

Stockholm,July2025

©EuropeanCentreforDiseasePreventionandControl,2025.Reproductionisauthorised,providedthesourceisacknowledged.

SURVEILLANCEREPORT

Haemophilusinfluenzaedisease

AnnualEpidemiologicalReportfor2023

Keyfacts

•In2023,5,234confirmedcasesofinvasiveHaemophilusinfluenzaediseasewerereportedintheEU/EEA,representingacontinuedincreasecomparedtothepreviousyear(3983in2022)andasubstantialrise

frompandemic-erafigures(1693in2021,1838in2020),coincidingwiththepost-COVID-19returntotypicalrespiratorydiseasetransmissionpatterns.

•Thenotificationrateroseto1.2casesper100000population,thehighestobservedinthepastfiveyears,upfrom0.9in2022and0.4inboth2020and2021.

•Age-specificratesremainedhighestamonginfantsunderoneyearofage(6.41per100000population),followedbythoseaged65yearsandolder(3.2per100000population).

•Serotypingdatawereavailablefor60%ofcases.Amongcaseswithknownserotype,non-capsulated

strainscontinuedtodominate,accountingfor81%ofinfections.Serotypefwasthemostfrequent

capsulatedstrain,responsiblefor6%(194cases)ofallcases,followedbyserotypeb5%(164cases)

•In2023,serotypeb(Hib)represented5%ofknownserotypedcases,reflectingaslightdeclinefrom

9.1%in2022.Thelowproportionofserotypeb(Hib)reportedcontinuestoreflectthestrongeffectoftheHibvaccinationprogrammesinEU/EEAcountries.

Introduction:

InvasiveHaemophilusinfluenzaeisabacteriumthatcancauseseverebacterialinfections,particularlyinthecaseofthetypebstrain,thataffectsbothchildrenandadults,withyoungchildrenbeingmostatrisk.Thebacteriacancauseanumberofseriousconditionsincludingmeningitis,septicaemia,pneumonia,andepiglottitis.[1].

InvasiveHaemophilusinfluenzae,particularlytypeB(Hib),causessevereinfectionssuchasmeningitis,

pneumonia,septicaemia,andepiglottitis,especiallyinyoungchildren.Humansaretheonlyknownreservoir,andtransmissionoccursthroughrespiratorydropletsorsecretions.Althoughtheincubationperiodisnotwelldefined,diseaseusuallydevelopswithinaweekofexposure.Themortalityratecanbeto5-10%inindustrialisedcountriesandashighas40%inlow-resourcesettings.Survivorsmayexperiencelong-termcomplications,including

neurologicalanddevelopmentalimpairments.SincetheintroductionoftheHibvaccineinthe1980s,routine

immunisationintheEU/EEAhasnearlyeradicatedHib-relatedmeningitisinyoungchildren.Nevertheless,vigilanceremainsessential,withtreatmentrelyingonantibiotics;antibioticprophylaxisisrecommendedforclosecontacts.

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Methods

Thisreportisbasedondatafor2023retrievedfromEpiPulseCaseson12March2025.EpiPulseCasesisanewlyintroducedsystemforthecollection,analysisanddisseminationofdataoncommunicablediseasesthatreplacedTheEuropeanSurveillanceSystem(TESSy)inOctober2024.Anoverviewofthenationalsurveillancesystemsisavailableonline[2].AsubsetofthedatausedforthisreportisavailablethroughECDC’sonlineSurveillanceatlasofinfectiousdiseasesanddownloadable[3].

In2023,30EU/EEAMemberStatesreporteddataoninvasiveH.influenzaediseasetoECDC.MostoftheMemberStatesreporteddatausingtheEUcasedefinition(CommissionImplementingDecision2018/945/EUof22June

2018oftheEuropeanParliamentandoftheCouncil)oracasedefinitioncompatiblewiththeEUcasedefinitionforconfirmedcases.ForGreecethecasedefinitionwasnotspecified/unknown,andGermanyusedanothercase

definition[2].ThemajorityofMemberStatesreporteddatafromcomprehensive,passivesurveillancesystemswithnationalcoverage.Belgiumreportedaggregateddata[2].

HaemophilusinfluenzaetypebvaccinationcoverageestimatespresentedinthisreportwereretrievedfromtheWHOGlobalHealthObservatorywebsite.[4]

Epidemiology

In2023,30EU/EEAcountriesreportedatotalof5234confirmedcasesofinvasiveHaemophilusinfluenzae

disease,markingacontinuedincreasefromthe3983casesreportedin2022,andnearlytriplingthenumbersseenin2021(1693)and2020(1838)(Table1).TheoverallnotificationratefortheEU/EEAreached1.2casesper100000population.ThehighestnotificationrateswereobservedinDenmark(2.3per100000),Lithuania(2.1),and

Sweden(2.1)(Table1,Figure1).

France(883cases),Germany(1456),andItaly(315)togetheraccountedfor51%(2663cases)ofallconfirmedcasesintheEU/EEA.Bycontrast,countriessuchasCroatia(1),Cyprus(2),Estonia(3)andMalta(2)continuedtoreportveryfewornocases,Lichtensteinreportedzerocasesin2023.

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Table1.ConfirmedHaemophilusinfluenzaediseasecasesandratesper100000populationbycountryandyear,EU/EEA,2019-2023

Country

2019

2020

2021

2022

2023

Number

Rate

Number

Rate

Number

Rate

Number

Rate

Number

Rate

ASR

Austria

64

0.7

28

0.3

31

0.3

77

0.9

115

1.3

1.1

Belgium

76

NRC

27

NRC

38

NRC

146

NRC

205

NRC

NRC

Bulgaria

3

0.0

0

0.0

0

0.0

1

0.0

2

0.0

0.0

Croatia

1

0.0

0

0.0

0

0.0

0

0.0

1

0.0

0.0

Cyprus

0

0.0

0

0.0

1

0.1

3

0.3

2

0.2

0.2

Czechia

25

0.2

22

0.2

10

0.1

46

0.4

54

0.5

0.5

Denmark

115

2.0

59

1.0

101

1.7

117

2.0

137

2.3

2.1

Estonia

3

0.2

2

0.2

1

0.1

7

0.5

3

0.2

0.2

Finland

77

1.4

41

0.7

15

0.3

78

1.4

55

1.0

0.9

France

694

1.2

399

0.7

434

0.7

731

1.2

883

1.4

1.4

Germany

951

1.1

509

0.6

361

0.4

983

1.2

1465

1.7

1.4

Greece

5

0.0

2

0.0

6

0.1

9

0.1

17

0.2

0.1

Hungary

24

0.2

10

0.1

15

0.2

40

0.4

65

0.7

0.6

Iceland

8

2.2

5

1.4

7

1.9

8

2.1

6

1.5

1.5

Ireland

63

1.3

31

0.6

16

0.3

65

1.3

71

1.3

1.3

Italy

185

0.3

76

0.1

66

0.1

191

0.3

315

0.5

0.5

Latvia

4

0.2

1

0.1

1

0.1

13

0.7

6

0.3

NRC

Liechtenstein

NDR

NRC

NDR

NRC

2

5.1

0

0.0

0

0.0

0.0

Lithuania

3

0.1

0

0.0

2

0.1

58

2.1

60

2.1

2.0

Luxembourg

0

0.0

3

0.5

3

0.5

10

1.5

11

1.7

1.7

Malta

3

0.6

0

0.0

0

0.0

0

0.0

2

0.4

0.4

Netherlands

227

1.3

203

1.2

166

0.9

320

1.8

316

1.8

1.6

Norway

98

1.8

40

0.7

58

1.1

133

2.5

126

2.3

2.2

Poland

102

0.3

78

0.2

52

0.1

149

0.4

264

0.7

0.7

Portugal

42

0.4

35

0.3

42

0.4

62

0.6

77

0.7

0.7

Romania

0

0.0

1

0.0

0

0.0

12

0.1

18

0.1

0.1

Slovakia

8

0.1

5

0.1

1

0.0

9

0.2

24

0.4

0.4

Slovenia

24

1.2

11

0.5

15

0.7

29

1.4

31

1.5

1.3

Spain

245

0.6

161

0.4

171

0.4

462

1.0

678

1.4

1.3

Sweden

259

2.5

89

0.9

78

0.8

224

2.1

225

2.1

1.9

EU/EEA(30

countries)

3309

0.8

1838

0.4

1693

0.4

3983

0.9

5234

1.2

1.0

UnitedKingdom

NDR

NRC

NDR

NRC

NA

NA

NA

NA

NA

NA

NA

EU/EEA(31

countries)

3309

0.8

1838

0.4

NA

NA

NA

NA

NA

NA

NA

Source:Countryreports.

NDR:Nodatareported.

NRC:Noratecalculated.

NA:Notapplicable.

Nodatafrom2020onwardswerereportedbytheUnitedKingdom,duetoitswithdrawalfromtheEUon31January2020.

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Figure1.ConfirmedHaemophilusinfluenzaediseasecasesper100000populationbycountry,EU/EEA,2023

Ageandgenderdistribution

In2023,invasiveHaemophilusinfluenzaediseaseshowedaclearage-relatedpattern.Thehighestnotificationratewasreportedininfantsunderoneyearofage(6.41per100000population).Ratesdeclinedsteeplythereafter:

1.49inchildrenaged1-4years,0.33inthoseaged5-14,and0.18inthe15-24agegroup.Agradualincrease

followedamongolderadults,withnotificationratesof0.41inthe25-44agegroup,0.77in45-64,and3.2amongthoseaged65andover.Casedistributionmirroredthistrend,withthose65yearsandoldercomprising58.7%ofallreportedcases,followedbyadultsaged45-64(18.6%).Despitetherelativelysmallproportionofcasesin

infants,thediseaseburdenperpopulationwashighestinthisagegroup,indicatingabimodaldistributionwithpeaksintheveryyoungandthoseover65years.

Acrossmostagegroups(allgroupsexcept15-24,25-44years),malesexhibitedhighernotificationratesthan

females.Themostpronounceddifferencewasobservedininfantsunderoneyearofage,withratesof7.3per100

000formalescomparedto5.4forfemales.Thismalepredominancepersistedacrosschildhoodandadultage

groups,althoughthedifferencenarrowedinthe15-44agerange,wherefemalesslightlyoutnumberedmalesinsomegroups.Amongadultsaged65andabove,themalenotificationrateremainedhigher(3.5vs2.9per

100000).(Figure2).

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Figure2.ConfirmedHaemophilusinfluenzaediseasecasesper100000population,byageandgender,EU/EEA,2023

Source:CountryreportsfromAustria,Belgium,Bulgaria,Croatia,Cyprus,Czechia,Denmark,Estonia,Finland,France,Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Liechtenstein,Lithuania,Luxembourg,Malta,theNetherlands,Norway,Poland,Portugal,Romania,Slovakia,Slovenia,Spain,andSweden.

Seasonalityandtrend

Figure3indicatesthatthedistributionofinvasiveHaemophilusinfluenzaecasesin2023returnedtoamoretypicalseasonalpattern,withthehighestnumberofcasesrecordedduringthewintermonths(late2022andearly2023),followedbyadeclinethroughthesummer.Towardtheendof2023,casenumbersbegantoriseagain,reflectingthere-emergenceofthecharacteristicwinterpeak.The12-monthmovingaveragecontinueditsupwardtrajectoryfrommid-2022,reachingapeakinearly2023beforeplateauing,confirmingasustainedperiodofelevated

transmission.

Figure4showsthemonthlycasecountsin2023comparedtothemeanandrangefromthepreviousfouryears

(2019-2022).Casenumbersstartedtheyearwellabovethefiveyearaverage,particularlyinJanuary,and

remainedelevatedthroughthefirstquarter.Duringthesummer,reportedcasesdroppedbutstayednearorjust

abovetheupperrangeofpreviousyears.FromSeptemberonward,casesbeganincreasingagain,andthenumberofcasesremainedabovethefiveyearaverage,butatthesametimebelowthemaximumnumberofcases

reportedforthesameperiodinthepastfouryears.

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Figure3.ConfirmedHaemophilusinfluenzaediseasecasesbymonth,EU/EEA,2019-2023

Source:CountryreportsfromAustria,Bulgaria,Croatia,Cyprus,Czechia,Denmark,Estonia,Finland,France,Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Luxembourg,Malta,theNetherlands,Norway,Poland,Portugal,Romania,Slovakia,

Slovenia,Spain,andSweden.

Figure4.ConfirmedHaemophilusinfluenzaediseasecasesbymonth,EU/EEA,2023and2019-2022

Source:CountryreportsfromAustria,Bulgaria,Croatia,Cyprus,Czechia,Denmark,Estonia,Finland,France,Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Luxembourg,Malta,theNetherlands,Norway,Poland,Portugal,Romania,Slovakia,

Slovenia,Spain,andSweden.

Serotype

In2023,therewere3149casesofinvasiveHaemophilusinfluenzaediseasecaseswithknownserotype(60%).Thenon-capsulatedwasthemaintypewith2552cases(81%),Serotypeb(Hib)wasregisteredin164cases(5%)andwasmoreapparentamongtheyoungest,particularlyinchildrenunderoneyearofage(33cases)whichrepresent(21%)ofthecaseswithknownserotypeinthisagegroup,childrenbetween1-4years(31cases)whichrepresent(20%)ofthecaseswithknownserotypeinthisagegroup.Serotypefaccountedfor6%ofcases(194cases),whileothertypeswereserotypee(4%),serotypeaaccountedfor2%(83cases),andotherserotypes(c,d)togetheraccountedforasmallerportionofcases,consistentlyacrossallagegroups(141casesintotal).(Figure5).Thehighestproportionofserotypeawasobservedinchildrenbelowtheageof5yearsandforserotypefthehighestproportionwereobservedinchildrenbetween1and4yearsandindividualsbetween45and64years.

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Figure5.SerotypedistributionofconfirmedHaemophilusinfluenzaediseasecasesbyagegroup,EU/EEA,2023

Source:CountryreportsfromAustria,Czechia,Denmark,Finland,France,Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Luxembourg,theNetherlands,Norway,Poland,Portugal,Slovakia,Slovenia,Spain,Sweden.

Figure6showsthenotificationratesper100000populationfordifferentserotypesofinvasiveHaemophilusinfluenzaefrom2019to2023.Non-capsulatedstrainsremainedthemostprevalentgroup,withnotificationratescontinuingtoriseannuallyandpeakingin2023at0.10per100000population.Forserotypebbetween2019and2023,serotypebincidencehasbeenatstablelevels,almostplateauing.Serotypesfandeshowedmorebutnotdramaticfluctuatingtrendsbetween2019and2023:serotypefdeclinedfromitspeakin2022(0.013)to0.012in2023,andserotypeeremainedstable(approximately0.006).serotypearemainedatalowratein2023(0.006)similartopreviousyears(2022:0.005,2021:0.006),howevermarkinganincreasingtrendfrom2019whereanotificationof(0.004)wasobserved.The'Other'serotypesgrouproseforasecondconsecutiveyear,reaching0.007in2023.Meanwhile,thenotificationrateforcaseswithunknownserotypeincreasedagainin2023to0.078per100000population,thehighestlevelinthefive-yearperiod.

Figure6.NotificationrateofconfirmedHaemophilusinfluenzaediseaseper100000population,byserotypeandyear,EU/EEA,2019-2023

Source:CountryreportsfromAustria,Czechia,Denmark,Finland,France,Germany,Greece,Hungary,Ireland,Italy,Liechtenstein,theNetherlands,Norway,Poland,Portugal,Slovenia,Spain,Sweden.

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Clinicalpresentation

In2023,outof5234confirmedcasesofinvasiveHaemophilusinfluenzaedisease,clinicalpresentationwasreportedfor2595cases(50%).Themostcommonpresentationwaspneumonia,recordedin638cases(25%),followedbysepticaemiawith606cases(23%).Meningitiswasreportedin346cases(13%),while56cases(2%)presentedwithbothmeningitisandsepticaemia.Lessfrequentmanifestationsincludedosteomyelitisorsepticarthritis(11cases;0.4%),epiglottitis(sixcases;0.2%),andcellulitis(12cases;0.5%).Asignificantproportionofcases-920(36%)-wereclassifiedunder、other’clinicalpresentations.Clinicalinformationremainedunknownorunreportedforhalfofthereportedcases(2639).

Outcome

In2023,theoutcomewasreportedfor2875cases(55%).Amongthese,248deathswererecorded,resultinginanoverallcasefatalityrate(CFR)of8.6%.Eightdeathsoccurredininfantsunderoneyearofage(CFR=6.7%),andthreedeathswerereportedamongchildrenaged1-4years(CFR=2.2%).Themajorityoffataloutcomeswerereportedinindividualsaged65yearsandolder,with198deathsamong1716casesinthisgroup(CFR=11.5%).

Whenconsideringtheoutcomebyserotype,CFRsvariedacrossdifferentgroups.ThehighestCFRwasobservedforserotypeeat12.8%(fivedeathsamong39cases),followedbyserotypebat8.2%(ninedeathsamong110cases),non-capsulatedstrainsat7.9%(139deathsamong1757cases),serotypefat5.0%(sevendeathsamong140cases),andserotypeaat3.5%(twodeathsamong57cases).Onedeathwasreportedforserotyped.

Whenindicated,themajorityoffatalcaseswerereportedamongunvaccinatedindividuals(n=128),correspondingtoacasefatalityrate(CFR)of10%.Amongthosewithknowntobevaccinatedwiththreedosesofthevaccine,twodeathswerereported(CFR=2.7%),whileonedeathoccurredinacasewithonlyonedose(CFR=3.7%).

Whenanalysingthefatalcases(n=248)peragegroupandvaccinationstatus,itisnotablethatthemajorityofthefatalityoccurredinunvaccinatedindividuals(n=128,52%),particularlyamongtheagegroups+65yearswhereunvaccinatedcasesaccountedfor102deaths(41%ofthetotal).For116deaths(38%)inthisagegroupthevaccinationinformationwasmissing.Those65yearsandoldercomprisednearly80%ofallfataloutcomes,followedbyagegroup45-64years(n=34,13.7%),whilechildren<1yearofagehadeightfatalcases(3.2%),andthreedeaths(1.2%)wererecordedforeachoftheagegroups(1-4years,and25-44years).Theagegroup5-14yearshadthelowestnumberoffatalcases(n=2,0.8%)

Vaccinationstatus

In2023,vaccinationstatuswasknownfor1468ofthe5234confirmedcases(28%)ofinvasiveHaemophilusinfluenzaedisease.Amongthosewithknownstatus,187cases(12.7%)hadreceivedatleastonedoseofaHib-containingvaccine,while1281cases(87.3%)wereunvaccinated.Thenumberofdosesreceivedvaried,with27caseshavingreceivedonedose,25havingreceivedtwodoses,75threedoses,43fourdoses,andonecasereceivedfivedoses.Vaccinationstatuswasunknownfor16cases(1.1%).

Amongtheserotypebcases(n=164),thevaccinationstatuswasknownfor(n=124,75%),sixcaseshadonedoseofthevaccine,thirteencaseshadtwodoses,twenty-threecaseshadthreeormoredoses,whilethevastmajorityofthecases(n=83,50%)werenotvaccinated,andfortycases(24%)hadunknownvaccinationstatus.

Vaccinationcoverage

Figure7presentstheWHO/UNICEFEstimatesofImmunizationCoverageforthirddoseofHaemophilusinfluenzaetypeb(Hib3)vaccineacrossEU/EEAcountriesin2023(WUENICestimates).MedianHib3coverageintheEU/EEAwas94%,withcountry-specificestimatesrangingfrom78%to99%.

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Figure7.VaccinationcoverageofthirddoseofHib-containingvaccine,EU/EEA2023(Source:WUENIC,WHO)

Discussion

In2023,theEU/EEAreported5234confirmedcasesofinvasiveHaemophilusinfluenzaedisease.Comparedtothepre-COVID-19pandemicperiod,thenumberofcasesin2023representsasignificantincreaseinthenumberofcasescomparedtothe2013-2018period(range2593–3849),inadditionitisthehighestnumberofcasesreportedinoneyearsincethesurveillanceonEU/EEAlevelstartedin1996[3].COVID-19publichealthcontrolmeasures[5,6]havebeenassociatedwithadeclineinthenotificationofcasesofinvasiveHaemophilusinfluenzaedisease.In

2023asinpreviousyears,thediseaseburdenremainedconcentratedamonginfantsunderoneyearandadultsaged

65yearsandover,underscoringthepersistentvulnerabilityoftheseagegroups[7].

Anotablyhighproportionofserotypebcaseswerereportedinchildrenlessthanfour-year-old.Ininfants,ourdatadidnotpermittodeterminewhichinfantsweretooyoungtobeeligibletothevaccineofifvaccinatedcasesaged1-4-year-oldreceivedaboosterdoseofthevaccine.Indeed,thethirddoseofvaccinationagainstHaemophilusinfluenzaediseasemayrepresentthefirstboosterorthethirddoseofaprimarycourse,dependingonthescheduleadaptedbythecountry(2+1or3+1).Theeffectivenessofeachprogrammetopreventthediseaseinyoungchildrenwillbenefittobefurtherdocumented[8,9].

Thecontinuedexpansionofnon-capsulatedH.influenzaestrainsin2023furtherconfirmstheirdominanceinthepost-Hibvaccineera[10].ThisshiftinserotypesmaybepartiallyattributedtostrainreplacementfollowingtheintroductionoftheHibvaccines,improveddetectionmethods,anddemographicchangessuchasincreasedsusceptibilityamongthose65yearsandolder[11].Similarly,serotypef,whichrepresented6%ofcasesin2023,continuestobethemostcommoncapsulatedtype,thoughitsnotificationratedeclinedslightlycomparedto2022.Moreover,anincreasingtrendhasalsobeenobservedincasesgroupedunder、other’serotypes,highlightingtheneedformoreexhaustiveanddetailedserotypingtobetterunderstandemergingpatterns.ThesedevelopmentssupportpreviousfindingsonserotypereplacementandunderscoretheadaptivenatureofH.influenzaeepidemiologyinthepost-Hibvaccineera[12,13].

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Forthedatacollectedin2023,thecasefatalityrate(CFR)amongcaseswithknownoutcomewas8.6%,theinfantsunderoneyearandolderadultscomprisingthemajorityoffataloutcomes,apatternconsistentwiththepreviousyears[7].Amongserotypes,thehighestCFRwasobservedinserotypee(12.8%),followedbyserotypeb(8.2%)andnon-capsulatedstrains(7.9%).TherelativelylowerCFRofserotypebcomparedtoserotypeemayreflectevolvinghostsusceptibilityorchangesindiseaseseverityprofiles[7,8],andahigherfrequencyofserotypeeinadultsover65years.

Thecompletenessofthedataregardingclinicalpresentation,vaccinationstatus,andoutcomewouldbenefitfromimprovement.In2023,clinicalpresentationwasknownforonlyhalfofthecases,withpneumoniaandsepticaemiawerethemostfrequentlyreportedpresentations,consistentwithhistoricaltrends[7].Regardingvaccination,datawereavailableforonly1in4ofcases,amongwhichthemajority(9ofevery10cases)wereunvaccinated,whichissimilartothetrendin2022.Moreover,theproportionofcaseswithunknownserotypeandunknownvaccinationstatusremainedhighin2023(approximately34%,and72%,respectively),limitingfullepidemiologicalunderstanding.

FortheEU/EEAcountries,Hibmedianvaccinationcoverage(thirddose)wasestimatedat94%in2023,whichissimilartothemedianvaccinationcoveragerecordedin2022and2021[4].Thissustainedhighcoveragehasbeeninstrumentalinmaintaininglowincidenceofserotypebdiseaseacrossallagegroups.Inlinewiththisobservation,Hib(serotypeb)accountedforonly5%ofserotypedcasesin2023,adecreasefrom9.1%in2022,andsignificantlylowerthanpre-vaccinationlevels.Thissustaineddeclinehighlightsthelong-termimpactofHibvaccinationinreducingmorbidityandmortalityinyoungchildren.

Theoccurrenceofbreakthroughinfectionsamongpartiallyandfullyvaccinatedchildren—particularlyinthoseunderoneyearofageandinagegroup1-4yearsofage—highlightstheneedforthecontinuesassessmentofHibvaccineeffectivenessandthetimingofprotectionduringinfancy[14].Thesefindingsunderscoretheimportanceofongoingsurveillanceandevaluationofimmunisationschedulestoensureoptimalprotectioninthemostvulnerableagegroups.

Historically,invasiveH.influenzaediseasepredominantlyinvolvedserotypebinfectionsinotherwisehealthychildren.However,followingthewidespreadadoptionofHibvaccinationacrossEU/EEAMemberStates—fullyintegratedsince2010—theepidemiologicallandscapehasshifted[15-17].Theongoingevolutioninserotypedistributiondemandsvigilantsurveillance,enhancedmicrobiologicalmonitoring,andcontinuedinvestmentinlaboratorycapacitytoensureaccuratedetectionandreporting.

Inconclusion,therisingburdenofnon-typebandnon-capsulatedstrainsrequirescontinuousmonitoring.HighimmunisationcoveragemustbemaintainedtopreventHibresurgence,particularlyamonginfants,whilealsoexploringthedevelopmentofexpanded-valencyorprotein-basedvaccinesthattargetabroaderspectrumofH.influenzaestrains[18,19].Thepost-pandemicperiodhighlightstheinterplaybetweenimmunitygaps,behaviouralchanges,andpathogendynamics,reinforcingtheneedforflexibleandinclusivevaccinepoliciesthataddressbothcurrentandemergingthreats.

Publichealthimplications

ThenumberofHaemophilusinfluenzaecasesintheEU/EEAcontinuedtorisein2023,buildingontheincreaseobservedin2022andmarkingasustainedreboundfromthesuppressedlevelsreportedin2020and2021,andover25%ofincreasecomparedtothenumberofcasesrecordedin2018.—Whileserotypebnotificationrateisplateauing,non-capsulatedandnon-typebstrainshaveincreasedinincidence.MaintaininghighHibvaccinationcoverageamonginfantsandyoungchildrenremainsessential,butmustnowbecoupledwithstrengthened

serotypesurveillance,considerationoffuturevaccinedevelopmenttargetingbroaderstrains,andimprovedprotectionstrategiesforvulnerableadultpopulations.

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References

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