Haemophilus influenzae

Transcription

1 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

2 Haemophilus influenzae type b Pathogenesis 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 Clinical Features* Epiglottitis 17% Meningitis 50% Pneumonia 15% Osteomyelitis 2% Arthritis 8% Cellulitis 6% Bacteremia 2% *prevaccination era

3 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

4 Haemophilus influenzae type b Epidemiology Reservoir Human Asymptomatic carriers Transmission Respiratory droplets Temporal pattern Communicability Peaks in Sept-Dec and March-May Generally limited but higher in some circumstances Incidence*of Invasive Hib Disease, Incidence Year *Rate per 100,000 children <5 years of age

5 Haemophilus influenzae type b, 1986 Incidence* by Age Group Incidence Age group (mos) *Rate per 100,000 population, prevaccine era Haemophilus influenzae type b United States, Incidence has fallen 99% since prevaccine era 341 confirmed Hib cases reported during (average of 68 cases per year) Most recent cases in unvaccinated or incompletely vaccinated children

6 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 Polysaccharide Conjugate Vaccines Stimulates T-dependent immunity Enhanced antibody production, especially in young children Repeat doses elicit booster response

7 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

8 Haemophilus influenzae type b Vaccine Routine Schedule Vaccine 2 mo 4 mo 6 mo mo HbOC x x x x PRP-T x x x x PRP-OMP x x x Haemophilus influenzae type b 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

9 Haemophilus influenzae type b 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 Haemophilus influenzae type b Vaccine Adverse Reactions Swelling, redness, or pain in 5%-30% of recipients Systemic reactions infrequent Serious adverse reactions rare

10 Haemophilus influenzae type b 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 Pneumococcal Disease S. pneumoniae first isolated by Pasteur in 1881 Confused with other causes of pneumonia until discovery of Gram stain in 1884 More than 80 serotypes described by 1940 First U.S. vaccine in 1977

11 Streptococcus pneumoniae Gram-positive bacteria 90 known serotypes Polysaccharide capsule important virulence factor Type-specific antibody is protective Pneumococcal Disease Clinical Syndromes Pneumonia Bacteremia Meningitis

12 Pneumococcal Pneumonia Clinical Features Abrupt onset Fever Shaking chills Pleuritic chest pain Productive cough Dyspnea, tachypnea, hypoxia Pneumococcal Pneumonia Estimated 175,000 hospitalizations per year in the United States Up to 36% of adult community-acquired pneumonia and 50% of hospitalacquired pneumonia Common bacterial complication of influenza and measles

13 Pneumococcal Bacteremia More than 50,000 cases per year in the United States Rates higher among elderly and very young infants Case-fatality rate ~20%; up to 60% among the elderly Pneumococcal Meningitis Estimated 3,000-6,000 cases per year in the United States Case-fatality rate ~30%, up to 80% in the elderly Neurologic sequelae common among survivors

14 Pneumococcal Disease in Children Bacteremia without known site of infection most common clinical presentation S. pneumoniae leading cause of bacterial meningitis among children younger than 5 years of age Highest rate of meningitis among children younger than 1 year of age Common cause of acute otitis media Burden of Pneumococcal Disease in Children* Syndrome Cases Bacteremia 13,000 Meningitis 700 Death 200 Otitis media 5,000,000 *Prior to routine use of pneumococcal conjugate vaccine

15 Pneumococcal Disease Epidemiology Reservoir Human carriers Transmission Respiratory Temporal pattern Winter and early spring Communicability Unknown Probably as long as organism in respiratory secretions Invasive Pneumococcal Disease Incidence by Age Group Rate* < Age Group (Yrs) *Rate per 100,000 population Source: Active Bacterial Core surveillance/eip Network

16 Children at Increased Risk of Invasive Pneumococcal Disease Functional or anatomic asplenia, especially sickle cell disease HIV infection Recipient of cochlear implant Out-of-home group child care African American children Alaska Native and American Indian children who live in Alaska, Arizona, or New Mexico Navaho children who live in Colorado and Utah Pneumococcal Disease Outbreaks Outbreaks not common Generally occur in crowded environments (jails, nursing homes) Persons with invasive disease often have underlying illness May have high fatality rate

17 Pneumococcal Vaccines valent polysaccharide vaccine licensed valent polysaccharide vaccine licensed (PPV23) valent polysaccharide conjugate vaccine licensed (PCV7) Pneumococcal Polysaccharide Vaccine Purified capsular polysaccharide antigen from 23 types of pneumococcus Account for 88% of bacteremic pneumococcal disease Cross-react with types causing additional 8% of disease

18 Pneumococcal Conjugate Vaccine Pneumococcal polysaccharide conjugated to nontoxic diphtheria toxin (7 serotypes) Vaccine serotypes account for 86% of bacteremia and 83% of meningitis among children younger than 6 years of age Pneumococcal Polysaccharide Vaccine Purified pneumococcal polysaccharide (23 types) Not effective in children younger than 2 years 60%-70% against invasive disease Less effective in preventing pneumococcal pneumonia

19 Pneumococcal Conjugate Vaccine Highly immunogenic in infants and young children, including those with high-risk medical conditions 97% effective against invasive disease caused by vaccine serotypes 73% effective against pneumonia 7% reduction in all episodes of acute otitis media Pneumococcal Polysaccharide Vaccine Recommendations Adults 65 years of age or older Persons 2 years or older with chronic illness anatomic or functional asplenia immunocompromised (disease, chemotherapy, steroids) HIV infection environments or settings with increased risk MMWR 1997;46(RR-8):1-24

20 Pneumococcal Conjugate Vaccine Recommendations All children younger than 24 months of age Unvaccinated children months with a high-risk medical condition MMWR 2000;49(RR-9):1-35 Pneumococcal Conjugate Vaccine Recommendations Doses at 2, 4, 6, months of age, booster dose at months of age Unvaccinated children >7 months of age require fewer doses MMWR 2000;49(RR-9):1-35

21 Pneumococcal Conjugate Vaccine Children aged months at high risk and previously vaccinated with PPV23 should receive 2 doses of PCV7 Children at high risk who previously received PCV7 should receive PPV23 at age 2 years of age MMWR 2000;49(RR-9):1-35 Pneumococcal Polysaccharide Vaccine Revaccination Routine revaccination of immunocompetent persons is not recommended Revaccination recommended for persons age >2 years at highest risk of serious pneumococcal infection Single revaccination dose >5 years after first dose MMWR 1997;46(RR-8):1-24

22 Pneumococcal Polysaccharide Vaccine Candidates for Revaccination Persons >2 years of age with: functional or anatomic asplenia immunosuppression transplant chronic renal failure nephrotic syndrome Persons vaccinated at <65 years of age MMWR 1997;46(RR-8):1-24 Pneumococcal Vaccines Adverse Reactions Local reactions polysaccharide 30%-50% conjugate 10%-20% Fever, myalgia polysaccharide <1% conjugate 15%-24% Severe adverse reactions rare

23 Pneumococcal Vaccines Contraindications and Precautions Severe allergic reaction to vaccine component or following prior dose of vaccine Moderate or severe acute illness Pneumococcal Polysaccharide Vaccine Missed Opportunities >65% of patients with severe pneumococcal disease had been hospitalized within preceding 3-5 years yet few had received vaccine May be administered simultaneously with influenza vaccine