Hepatitis B: Global Epidemiology and

Prevention Strategies

Components of Strategies to Components of Strategies to Prevent HBV TransmissionPrevent HBV Transmission

• Hepatitis B immunization

– Universal infant immunization

– Prevent perinatal transmission

– Catch-up immunization

• Prevent nosocomial HBV transmissionPrevent nosocomial HBV transmission

Hepatitis B Virus Infection Hepatitis B Virus Infection Global Disease BurdenGlobal Disease Burden

• 2,000 million have markers of 2,000 million have markers of current or past infectioncurrent or past infection

• 350 million have chronic infection350 million have chronic infection– 15%-25% will die from chronic liver

disease (liver cancer and cirrhosis)– about 750,000 deaths per year

Outcome of HBV Infection Depends on Age of Infection

Young children• <10% get sick when first infected• chronic infection:

•80-90% at age < 1 year•30-50% at age 1-4 years

• 25% die from liver cancer/cirrhosis

Adults– 30-50% get sick when first infected– 2-6% develop chronic infection– 15% die from liver cancer/cirrhosis

Geographic Distribution of Chronic HBV Infection

HBsAg Prevalence

8% - High 2-7% - Intermediate <2% - Low

• High (8%): 45% of global population– lifetime risk of infection >60%– early childhood infections common

• Intermediate (2%-7%): 43% of global population– lifetime risk of infection 20%-60%– infections occur in all age groups

• Low (<2%): 12% of global population– lifetime risk of infection <20%– most infections occur in adult risk groups

Global Patterns of Chronic HBV Infection

Global Patterns of Chronic HBV Infection

Routes of HBV TransmissionRoutes of HBV Transmission

Age Group Route(s) of Infection

Newborn •mother to infant

•child to child •unsafe injections

Childhood

Adolescent/Adult

•sexual contact•injecting drug use•unsafe injections

EndemicityLow Int High

++

++++

+ + +

++

++ -

++++ +++ -

++

++

+++ +

++ ++ +/-

Age of acquisition of Age of acquisition of chronic HBV infections by chronic HBV infections by

endemicityendemicityLow Intermediate High

Perinatal Childhood Adolescent/Adult

Hepatitis B Immunization Hepatitis B Immunization ProgramsPrograms

ObjectiveObjectivePrevent chronic HBV infections

•prevent chronic liver disease•reduce the reservoir for transmission of new infections

Components of Strategies to Components of Strategies to Prevent HBV TransmissionPrevent HBV Transmission

• Hepatitis B immunization

– Universal infant immunization

– Prevent perinatal transmission

– Catch-up immunization

• Prevent nosocomial HBV transmissionPrevent nosocomial HBV transmission

Hepatitis B Vaccination TargetsHepatitis B Vaccination Targets45th World Health Assembly, 199245th World Health Assembly, 1992

Integrate hepatitis B vaccine into national Integrate hepatitis B vaccine into national childhood vaccination programschildhood vaccination programs

•By 1995 in countries with HBsAg prevalence 8%

•By 1997 in all countries

Global Status of Hepatitis B Immunization Policyas of January 2001

Implemented (129)

Not implemented (85)

February 20, 2001

The boundaries and names shown and the designations used on this map do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement.

Hep B Vaccine Implementation in GFCV-Eligible Countries*

Not yet eligible - DTP3<50% (N=16)

Approved (N=24)

Application pending (N=16)

Implemented (N=18)

*4th tranche-June 2001

Impact of Hepatitis B Immunization Impact of Hepatitis B Immunization

Reduces prevalence of chronic HBV infection in immunized cohorts

<1% in areas with low rate of perinatal transmission

<2% in areas with high rate of perinatal transmission

Reduces infection "pressure"

Unvaccinated persons with chronic infection lose HBeAg and become less infectious

Results in greater than expected impact on transmission

Reduces liver cancer

Effect of Routine Infant Immunization on the Effect of Routine Infant Immunization on the Prevalence of Chronic HBV InfectionPrevalence of Chronic HBV Infection

Chronic HBV infection

Study Year No.Tested

Age(yrs)

Vaccine Coverage

BeforeProgram

After Program

Alaska 1995 268 1-10 96% 16% 0%

Taiwan 1994 424 7-10 73% 10% 1.1%

Samoa 1996 435 7-8 87% 7% 0.5%

Lombok 1994 2519 4 > 90% 6.2% 1.9%

Saipan 1994 200 3-4 94% 9% 0.5%

Ponape 1994 364 3-4 82% NA 1.0%

Micronesia 1992 544 2 40% 12% 3.0%

Age of Acquisition of Chronic Age of Acquisition of Chronic HBV Infections in High Endemic HBV Infections in High Endemic

CountriesCountries

Perinatal 10-30

Young children 65-80

Adolescents/Adults <5

% of Chronic Infections

Age of Acquisition

Strategies to Prevent Strategies to Prevent Perinatal HBV Transmission (1)Perinatal HBV Transmission (1)

Selective Immunoprophylaxis • Screen pregnant women for HBsAg• Give prophylaxis to infants of HBsAg+ mothers

Pros– prophylaxis targeted to infants that need it– can administer both HBIG/HepB vaccine Issues– Requires extensive resources to screen pregnant

women/track infants of HBsAg+ mothers– Few successful programmes

Strategies to Prevent Strategies to Prevent Perinatal HBV Transmission (2)Perinatal HBV Transmission (2)

Integrate as Component of Routine Infant VaccinationIntegrate as Component of Routine Infant Vaccination

• Vaccinate all infants beginning at birth

Pros

– No need to screen pregnant women

– Very feasible to implement if a high proportion of infants are born in health care facilities

Issues

– Need to assure effective HepB vaccine delivery for all infants

Priority of Giving a Birth Dose

Issues to consider

• Contribution of perinatal transmission to overall hepatitis B disease burden

• Feasibility of delivering the first dose at birth

– Currently, most feasible in hospitals

– With availability of Uniject, it may be feasible to give HepB vaccine to infants delivered at home

Priority of Perinatal Hepatitis B PreventionHigh proportion of chronic infections acquired perinatally (e.g.,

SE Asia)

• A birth dose should be given when feasible (e.g., in birthing hospitals)

• Efforts should be made to administer HepB vaccine to infants who deliver at home

Low proportion of chronic infections acquired perinatally (e.g., Africa)

• A birth dose may be considered after evaluating disease burden, cost-effectiveness, and feasibility

Priority of Catch-up Immunization

High endemicity of HBV infection

• Most chronic infections acquired before age 5 years

• Immunizing infants will rapidly reduce transmission

• Catch-up immunization not generally needed

Priority of Catch-up Immunization II

Lower endemicity of HBV infection

• May be large disease burden from infections acquired in older age groups

• Immunizing infants alone may not substantially lower disease incidence for decades

• Catch-up immunization may be desirable:

– single-age cohorts (e.g., routine adolescent immunization)

– high risk groups (e.g., MSM, IDUs, persons w/STDs)• STD clinics, correctional facilities, drug treatment

Components of Strategies to Components of Strategies to Prevent HBV TransmissionPrevent HBV Transmission

• Hepatitis B immunization

– Universal infant immunization

– Prevent perinatal transmission

– Catch-up immunization

• Prevent nosocomial HBV transmissionPrevent nosocomial HBV transmission

HBV Transmission in Healthcare HBV Transmission in Healthcare SettingsSettings

ProviderProvider

ProviderProviderPatientPatient

•Unsafe injection practices•Reuse of contaminated medical equipment •Blood transfusion

PatientPatient

PatientPatient

PatientPatient

•Needlestick/sharps injuries

•Invasive surgical procedures

•Use safe injection practices•Use sterile equipment •Screen blood supply

•Use standard precautions•Vaccinate HCW

•Use standard precautions