Rational use of Haemophilus influenzae type b vaccine.

Haemophilus influenzae type b (Hib) is a major cause of serious bacterial infection in early childhood. In many developed countries it is the commonest cause of bacterial meningitis in children under 5 years of age. Serum antibodies to the polyribosylribitol phosphate (PRP) capsule, the main virulence factor of Hib, are protective, but the early vaccines containing purified PRP were poorly immunogenic in young children. However, 'second generation' protein conjugate vaccines have been shown to be immunogenic, effective and safe in young children. No serious adverse reactions to Hib vaccine have been reported to date. Clinically, the vaccine is indicated in the first few months of life and can be given at the same time as a primary course of diphtheria, pertussis and tetanus (DPT) immunisation. The vaccine should be given by deep subcutaneous or intramuscular injection. The only specific contraindication is a history of severe local reaction or a general reaction to previous Hib vaccination. Routine immunisation of infants under 6 months of age against Hib has become part of the regular primary schedule in many countries. In Finland this has resulted in a dramatic decline in Hib meningitis.