Haemophilus influenzae type b

n. (Abbr. Hib)
A rod-shaped, gram-negative bacterium found in the human respiratory tract that causes acute respiratory infections, such as pneumonia, and other diseases, especially meningitis in young children.

[New Latin Haemophilus īnfluenzae, species name : Greek haima, blood + Greek -philos, -philous + New Latin īnfluenzae, genitive of īnfluenza, influenza.]

This vaccine is prepared from polysaccharides (sugars) contained in the capsule of Haemophilus influenzae type b (Hib). Hib can cause otitis media, pneumonia, septic arthritis, meningitis, and other severe systemic infections. The earliest Hib vaccines contained only the polysaccharides. They did not reliably induce immunity in infants, who are at highest risk for Hib disease, and did not induce immunologic memory. Current Hib vaccines are prepared by conjugating the polysaccharide with some protein (such as tetanus toxoid), which enhances its ability to protect infants and induces immunologic memory. The vaccine is typically administered in a series of two or three doses separated by two months with subsequent doses administered approximately one year and four years later. Ninety percent or more of infants immunized are protected. Vaccine-induced immunity lasts at least through age six, by which time the risk of Hib disease is quite low. There are no known serious adverse events attributable to Hib vaccine.

(SEE ALSO: Child Health Services; Communicable Disease Control; Immunizations)

Bibliography

Centers for Disease Control and Prevention (1993). "Recommendations for Use of Haemophilus B Conjugate Vaccines and a Combined Diphtheria, Tetanus, Pertussis, and Haemophilus B Vaccine: Recommendations of the Advisory Committee on Immunization Practices (ACIP)." Morbidity and Mortality Weekly Report 42:1–15.

— ALAN R. HINMAN

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