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