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.

SURVEILLANCEREPORTAnnualepidemiologicalreportfor2023

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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.

SURVEILLANCEREPORTAnnualepidemiologicalreportfor2023

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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).

5

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.

6

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.

SURVEILLANCEREPORTAnnualepidemiologicalreportfor2023

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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%.

9

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].

SURVEILLANCEREPORTAnnualepidemiologicalreportfor2023

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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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https://atlas.ecdc.europa.eu/public/index.aspx?Dataset=27&HealthTopic=37

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