Haemophilus influenzae type b conjugate vaccines
Wherever thorough studies have been performed, Haemophilus influenzae type b (Hib) has been shown to be an important cause of childhood meningitis and a major cause of bacterial pneumonia in children. Although little population-based incidence data are available from most of Asia and the Newly Independent States, Hib is estimated to cause at least 3 million cases of serious disease and hundreds of thousands of deaths annually, worldwide. The most important manifestations of Hib disease, namely pneumonia and meningitis, are seen mainly in children under 5 years of age, particularly infants. Currently, several different Hib vaccines, all conjugate vaccines, are on the market. These vaccines are now used as part of routine childhood vaccination programmes in more than 20 countries including Canada, the United States of America, Australia and New Zealand, and many countries of western Europe, and have proven to be highly efficacious and virtually free from serious side-effects. Also, excellent results of trials or national introduction in Chile, Uruguay, and the Gambia show that Hib conjugate vaccines are effective in developing country settings. Because these vaccines significantly reduce nasopharyngeal carriage, a herd effect is achieved through Hib vaccination.