Acute epiglottitis is an uncommon but dangerous bacterial infection of the supraglottis, but pre-dominantly the loose connective tissue of the epiglottis. An 8-year review of cases in the United States from 1998 to 2006 showed a mortality rate, from an average of about 4,000 cases per year, of about 1%.
19.1 Hib Vaccine
The Haemophilus influenzae type B (Hib) conjugate vaccine is a biosynthetic vaccine. Antibodies against the polysaccharide capsule of H. influenzae, namely polyribosylribitol phosphate (PRP), provide immunity against H. influenzae infection and so it was initially thought that purified PRP would be an excellent vaccine and this was introduced in the 1980s. In practice, purified PRP stimulated a poor immune response due to the recognition of PRP by B cells but not T cells. It was recognised that when PRP was linked with a highly immunogenic protein carrier, a much stronger immune response occurred due to T and B cells recognising the covalent PRP. This conjugated vaccine has been given in the United Kingdom since 1992, as part of the childhood vaccination programme. It is given as a 1:5 vaccine (also includes diphtheria, tetanus, whooping cough and polio) at 2, 3, and 4 months and then at 12 months as a 2:1 vaccine with Men C. Its introduction has seen more than a 90% reduction in the incidence of meningitis, pneumonia and epiglottitis as well as a reduction in acute otitis media.
Prior to the introduction of the Hib vaccine as purified PRP in the 1980s and as the conjugate vaccine in the 1990s, epiglottitis was usually seen in children, particularly between the ages of 3 and 5, but also affecting adults. For example, in Sweden in 1987 prior to the introduction of the Hib conjugate vaccine the incidence was 20.9 per 100,000 in children aged up to 5 years but fell to 0.9 per 100,000 by 1996 after the Hib vaccination was introduced in 1992. The incidence has continued to fall as take up levels have increased. In Denmark, where immunisation is compulsory, the incidence has fallen in children to 0.2 cases per 100,000. In adults, the incidence in developed nations has remained constant at 1 to 2 cases per 100,000, presumably because Hib is routinely offered only to children.