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Haemophilus influenzae Serotype b (Hib) Disease

Disease Listing | General Information | Technical Information | Additional Information

Clinical Features Invasive disease caused by Haemophilus influenzae type b can affect many organ systems. The most common types of invasive disease are pneumonia, occult febrile bacteremia, meningitis, epiglottitis, septic arthritis, cellulitis, otitis media, purulent pericarditis, and other less common infections such as endocarditis, and osteomyelitis.
Etiologic Agent Haemophilus influenzae serotype b.
Incidence Due to routine use of the Hib conjugate vaccine since 1990, the incidence of Hib disease in infants and young children has decreased by 99% to fewer than 1 case per 100,000 children under 5 years of age. In the United States, Hib disease occurs primarily in underimmunized children and among infants too young to have completed the primary immunization series. In developing countries, where routine vaccination with Hib vaccine is not widely available, Hib remains a major cause of lower respiratory tract infections in infants and children.
Sequelae 3%-6% of cases are fatal; up to 20% of surviving patients have permanent hearing loss or other long-term sequelae.
Transmission Direct contact with respiratory droplets from nasopharyngeal carrier or case patient.
Risk Groups Infants and young children , household contacts, and day-care classmates. American Indian/Alaska Native populations are also at increased risk.
Surveillance National surveillance is conducted through NETSS. Active laboratory-based surveillance is conducted by the Emerging Infection Program's Active Bacterial Core surveillance (ABCs).
Trends Since licensure of conjugate vaccines for infants (1990) and children (1987), rates of disease among children younger than 5 years old have declined by more than 95% in the United States, while rates for adults have remained stable. However, rates of disease among Alaskan natives remain higher than elsewhere in the United States.
Challenges Elimination of persistent Hib disease in the United States. Currently available conjugate vaccines differ in immuno-genicity in very young children and possibly in duration of antibody persistence, raising questions about long-term efficacy (more than 5 years), optimal use, and schedules. Monitoring the possible emergence of disease due to other serotypes. Problems with serotyping of H. influenzae in state health departments. Development of rapid molecular assays for detection and molecular subtyping of all Hi strains. More recently, following the recall of certain lots of Hib vaccine and Hib vaccine shortage, CDC recommended that providers temporarily defer administering the routine Hib vaccine booster dose administered at age 12-15 months, except to children in specific groups at high risk and American Indian/Alaska Native children. The cost of Hib conjugate vaccines has limited their use in developing countries even though Hib is a major cause of morbidity and mortality.
Opportunities Evaluating the characteristics of Hib vaccines associated with prevention of carriage and invasive disease will facilitate application of this technology to development of conjugate vaccines for other organisms with polysaccharide capsules (such as the meningococcus, pneumococcus, and group B streptococcus). Further evaluation of herd immunity effects may lead to insight into vaccination strategies that optimize protection against invasive disease and transmission of Hib organisms.
Date: April 4, 2008
Content source: National Center for Immunization and Respiratory Diseases: Division of Bacterial Diseases
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