Worldwide Haemophilus influenzae type b disease at the beginning of the 21st century: Global analysis of the disease burden 25 years after the use ofthe polysaccharide vaccine and a decade after the advent of conjugates

Vaccination against Haemophilus influenzae type b (Hib) diseases began a qu arter of a century ago with a polysaccharide vaccine; this vaccine was foll owed by four different conjugates 10 years later. In this review, the burde n of global Hib disease is quantified following this 25-year period of vacc ine availability to determine the potential impact of conjugate vaccines. T his task was accomplished by analysis of data available in 10 languages in 75 geographical regions of over 50 countries. All severe Hib diseases, not only meningitis, were characterized and special attention was paid to the m ost vulnerable age group, ie., children aged 0 to 4 years. Prior to vaccina tion the weighted worldwide incidence of meningitis in patients younger tha n 5 years was 57/100,000, and for all Hib diseases except nonbacteremic pne umonia, it was 71/100,000, indicating 357,000 and 445,000 cases per year, r espectively. At feast 108,500 of these children died. For all age groups co mbined, there were 486,000 cases of Hib disease, excluding pneumonia, with 114,200 deaths and probably an equal number of sequelae per annum. If the f igures for nonbacteremic pneumonia are included a conservative estimate is that over 2.2 million cases of infection and 520,000 deaths from Hib diseas e occurred worldwide, but the true numbers might have been greater Despite these large numbers and availability of safe and efficacious vaccines, only 38,000 cases annually are prevented-a meager 8% or less than a 2% reductio n in cases, depending on whether nonbacteremic pneumonia is included in the calculations. Although vaccination has had great success in some affluent countries, the current level of activity has had a very small impact global ly. The use of conjugates, preferably with a reduced number of doses and in combination with other vaccines or perhaps in fractional doses, should be extended to less privileged countries, where most Hib disease occurs.