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Haemophilus influenzae type B and Hib Vaccine
Dr Seyed Mohsen ZahraeiCenter for Communicable Disease Control
Haemophilus influenzae type b Epidemiology
• Reservoir Human Asymptomatic carriers
• Transmission Respiratory droplets
• Temporal pattern Peaks in Sept-Dec and March-May
• Communicability Generally limited but higher in some circumstances
0
5
10
15
20
2530
35
40
45
50
1987 1991 1995 1999
Inci
denc
eEstimated Incidence* of Invasive Hib
Disease, 1987-2000
*Rate per 100,000 children <5 years of age
0
20
40
60
80
100
120
140
160
180
200
0-1 12-13 24-25 36-37 48-49 60
Age group (mos)
Cas
esHemophilus influenzae type b, 1986
Incidence by age group
Haemophilus influenzae type b – United States, 1996-2000
• Incidence has fallen 99% since prevaccine era
• 341 confirmed Hib cases reported during 1996-2000 (average of 68 cases per year)
• Most recent cases in unvaccinated or incompletely vaccinated children
Hemophilus influenzae type bRisk factors for invasive disease
• Exposure factors–household crowding– large household size–day care attendance– low socioeconomic status– low parental education–school-aged siblings
• Host factors– race/ethnicity–chronic disease
Haemophilus influenzae type bPolysaccharide Vaccine
• Available 1985-1988
• Not effective in children <18 months of age
• Effectiveness in older children variable
Polysaccharide Vaccines
• Age-related immune response
• Not consistently immunogenic in children 2 years old
• No booster response
• Antibody with less functional activity
Polysaccharide Conjugate Vaccines
• Stimulates T-dependent immunity
• Enhanced antibody production, especially in young children
• Repeat doses elicit booster response
• Antibody is biologically active in vitro
Haemophilus influenzae type b Conjugate Vaccines
• Pure polysaccharide vaccines (1985-1989) not effective in infants
• 3 conjugate vaccines licensed for use in infants in USA
• Chemically and immunologically different
PRP-D ProHIBITHbOC HibtiterPRP-T ActHIB, OmniHIB, TriHIBitPRP-OMP PedvaxHIB, COMVAX
Conjugate Hib Vaccines
Vaccine 2 mo 4 mo 6 mo 12-18 mo
HbOC x x x x
PRP-T x x x x
PRP-OMP x x x
Haemophilus influenzae type b VaccineRoutine Schedule
• Vaccination at <6 weeks of age may induce immunologic tolerance to Hib antigen
• Minimum age 6 weeks
• Minimum interval 4 weeks for primary series doses
Haemophilus influenzae type b Vaccine
Haemophilus influenzae type b VaccineInterchangeability
• All conjugate Hib vaccines interchangeable for primary series and booster dose
• 3 dose primary series if more than one brand of vaccine used
Map of countries have introduced Hib vaccine
March 2014
Haemophilus influenzae type b VaccineDelayed Vaccination Schedule
• Children starting late may not need entire 3 dose series
• Number of doses child requires depends on current age
• All children 12-59 months of age need at least 1 dose