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Article title: Haemophilus influenzae Serotype b (Hib) Disease: DBMD
Conditions: Haemophilus influenzae B
Clinical Features In the United States and other industrialized countries, more than one-half of Haemophilus influenzae serotype b (Hib) cases present as meningitis with fever, headache, and stiff neck. The remainder present as cellulitis, arthritis, or sepsis. In developing countries, Hib is the second leading cause of bacterial pneumonia deaths in children as well. Etiologic Agent Haemophilus influenzae serotype b. Incidence During 1980-1990, incidence was 40-100/100,000 children < 5 yrs old in the United States. In 1995, since use of Hib conjugate vaccine, incidence is < 2 cases /100,000 children . Hib remains a major cause of lower respiratory tract infections in infants and children in developing countries where vaccine is not widely used. Sequelae 3%-6% of cases are fatal; up to 20% of surviving patients have permanent hearing loss. Transmission Direct contact with respiratory droplets from nasopharyngeal carrier or case patient. Risk Groups Infants and young children, household contacts, and day-care classmates. Surveillance National surveillance is conducted through NETSS and the National Bacterial Meningitis and Bacteremia Reporting System. Active laboratory-based surveillance is conducted in Emerging Infections Program sites and other areas of the United States. Trends Since licensure of conjugate vaccines for infants (1990) and children (1987), rates of disease among children <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 Development of strategies for elimination of Hib disease in the U.S. 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 (>5 years), optimal use, and schedules. 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.
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