B 型嗜血感冒桿菌感染及 其疫苗 衛生署疾病管制局 中區傳染病防治醫療網 王任賢指揮官
Haemophilus influenzae type b Severe bacterial infection, particularly among infants During late 19th century believed to cause influenza Immunology and microbiology clarified in 1930s
Haemophilus influenzae Aerobic gram-negative bacteria Polysaccharide capsule Six different serotypes (a-f) of polysaccharide capsule 95% of invasive disease caused by type b
Pathogenesis of Hib Organism colonizes nasopharynx In some persons organism invades bloodstream and cause infection at distant site Antecedent upper respiratory tract infection may be a contributing factor
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
Incidence*of Invasive Hib Disease, 1990-2004 25 20 Incidence 15 10 5 0 1990 1992 1994 1996 1998 2000 2002 2004 Year *Rate per 100,000 children <5 years of age
Haemophilus influenzae type b, 1986 Incidence* by Age Group Incidence 200 180 160 140 120 100 80 60 40 20 0 0-1 12-13 24-25 36-37 48-49 60 Age group (mos) *Rate per 100,000 population, prevaccine era
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
Haemophilus influenzae type b Risk Factors for Invasive Disease Exposure factors household crowding large household size child care attendance low socioeconomic status low parental education school-aged siblings Host factors race/ethnicity chronic disease
Haemophilus influenzae type b Clinical Features* Epiglottitis 17% Meningitis 50% Pneumonia 15% Osteomyelitis 2% Arthritis 8% Cellulitis Bacteremia 6% 2% *prevaccination era
Haemophilus influenzae type b Meningitis Accounted for approximately 50%-65% of cases in the prevaccine era Hearing impairment or neurologic sequelae in 15%-30% Case-fatality rate 2%-5% despite of effective antimicrobial therapy
Haemophilus influenzae type b Medical Management Hospitalization required Treatment with an effective 3rd generation cephalosporin, or chloramphenicol plus ampicillin Ampicillin-resistant strains now common throughout the United States
Infectious Period As long as the organism is present, even in the absence of nasal discharge. Noninfectious within 24 to 48 hours after the start of effective antibiotics.
Haemophilus influenzae type b Polysaccharide Vaccine Available 1985-1988 Not effective in children younger than 18 months of age Effectiveness in older children variable
Polysaccharide Vaccines Age-related immune response Not consistently immunogenic in children 2 years of age and younger 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
Haemophilus influenzae type b Conjugate Vaccines 3 conjugate vaccines licensed for use in infants as young as 6 weeks of age All utilize different carrier proteins 2 combination vaccines available that contain Hib vaccine
Conjugate Hib Vaccines HbOC PRP-T PRP-OMP Hibtiter ActHIB, TriHIBit PedvaxHIB, Comvax
Hib Vaccine: Routine Schedule 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
Hib Vaccine Recommended interval 8 weeks for primary series doses Minimum interval 4 weeks for primary series doses Vaccination at younger than 6 weeks of age may induce immunologic tolerance to Hib antigen Minimum age 6 weeks
Hib Vaccine Interchangeability All conjugate Hib vaccines interchangeable for primary series and booster dose 3 dose primary series if more than one brand of vaccine used
Hib Vaccine Delayed Vaccination Schedule Children starting late may not need entire 3 or 4 dose series Number of doses child requires depends on current age All children 15-59 months of age need at least 1 dose
Lapsed Immunization Children who have fallen behind schedule with Hib vaccine may not need all the remaining doses of a 3 or 4 dose series The number of doses needed to complete the series should be determined using the catch-up schedule*, published annually with the childhood schedule *available on the NIP website at www.cdc.gov/nip
Hib Vaccine Detailed Schedule for Unimmunized Children Vaccine Age at 1st Dose (months) Primary series Booster HbOC/PRP-T 2-6 3 doses, 2 m apart 12-15 months 7-11 2 doses, 2 m apart 12-18 months 12-14 1 dose 2 months later 15-59 1 dose -- PRP-OMP 2-6 2 doses, 2 m apart 12-15 months 7-11 2 doses, 2 m apart 12-18 months 12-14 1 dose 2 months later 15-59 1 dose --
Hib Vaccine Vaccination Following Invasive Disease Children younger than 24 months may not develop protective antibody after invasive disease Vaccinate during convalescence Complete series for age
Hib Vaccine Use in Older Children and Adults Generally not recommended for persons older than 59 months of age Consider for high-risk persons: asplenia, immunodeficiency, HIV infection, HSCT One pediatric dose of any conjugate vaccine
Combination Vaccines Containing Hib DTaP Hib TriHIBit Hepatitis B Hib Comvax
TriHIBit ActHIB reconstituted with Tripedia Not approved for the primary series at 2, 4, or 6 months of age Approved for the fourth dose of the DTaP and Hib series only Primary series Hib doses given as TriHIBit should be disregarded
TriHIBit May be used as the booster dose of the Hib series at 12 months of age or older following any Hib vaccine series* Should not be used if child has receive no prior Hib doses *booster dose should follow prior dose by at least 2 months
Comvax Hepatitis B-Hib combination Use when either or both antigens indicated at 6 weeks of age or older Not licensed for use if mother HBsAg+ Spacing and timing rules same as for individual antigens
Comvax Minimum Intervals Package insert implies 8-11-month interval between doses 2 and 3 This applies only if dose 2 given at 4 months of age Minimum interval if not on schedule is TWO months (minumum age 12 months)
Hib Vaccine: Adverse Reactions Swelling, redness, or pain in 5%-30% of recipients Systemic reactions infrequent Serious adverse reactions rare
Hib Vaccine Contraindications and Precautions Severe allergic reaction to vaccine component or following a prior dose Moderate or severe acute illness Age less than 6 weeks
Public Health Action When a case is reported: 1. Assure case is on respiratory droplet precautions. 2. Report to CDC and local DOH
Public Health Action Identify contacts of index case for whom prophylaxis is recommended. 1. All suitable household contacts, including adults, when the household contains a contact that is younger than 48 months (four years) of age whose immunization status with conjugate vaccine is incomplete. 2. All members of a household with a child younger than 12 months of age, even if the primary series has been given.
Public Health Action 3. All occupants of a household with an immunocompromised child, irrespective of the child s Hib immunization status. 4. Nursery and child care contacts, irrespective of age, when two or more cases of invasive disease have occurred within 60 days. 5. Index case, if treated with regimes other than cefotaxime or ceftriaxone, should receive chemoprophylaxis before discharge
Public Health Action Chemoprophylaxis is not recommended for the following: 1. Occupants of household with no children younger than four years of age other than the index patient. 2. Occupants of households when all household contacts younger than 48 months of age have completed their Hib immunization series. 3. Nursery and child care center contacts of one index case, especially those older than two years of age. 4. Pregnant women
Public Health Action
Public Health Action Prevent secondary cases by: a. Isolation of the case until 24 hours after the start of appropriate chemoprophylaxis. b. Appropriate prophylaxis of contacts.
Public Health Action Bring unvaccinated or under-vaccinated infants/toddlers up to date with their immunization.
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