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Review
, 13 (2), 302-17

Worldwide Haemophilus Influenzae Type B Disease at the Beginning of the 21st Century: Global Analysis of the Disease Burden 25 Years After the Use of the Polysaccharide Vaccine and a Decade After the Advent of Conjugates

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Review

Worldwide Haemophilus Influenzae Type B Disease at the Beginning of the 21st Century: Global Analysis of the Disease Burden 25 Years After the Use of the Polysaccharide Vaccine and a Decade After the Advent of Conjugates

H Peltola. Clin Microbiol Rev.

Abstract

Vaccination against Haemophilus influenzae type b (Hib) diseases began a quarter of a century ago with a polysaccharide vaccine; this vaccine was followed by four different conjugates 10 years later. In this review, the burden of global Hib disease is quantified following this 25-year period of vaccine availability to determine the potential impact of conjugate vaccines. This 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 most vulnerable age group, i.e., children aged 0 to 4 years. Prior to vaccination, the weighted worldwide incidence of meningitis in patients younger than 5 years was 57/100,000, and for all Hib diseases except nonbacteremic pneumonia, it was 71/100,000, indicating 357,000 and 445,000 cases per year, respectively. At least 108,500 of these children died. For all age groups combined, 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 figures for nonbacteremic pneumonia are included, a conservative estimate is that over 2.2 million cases of infection and 520,000 deaths from Hib disease 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% reduction 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 globally. 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.

Figures

FIG. 1
FIG. 1
Worldwide spectrum of all classical (nonbacteremic pneumonia excluded) Hib diseases, taken from data for 3,931 patients in 21 studies from various parts of the world.
FIG. 2
FIG. 2
Worldwide incidence per 100,000 per year of Hib meningitis for children aged 0 to 4 years before the conjugate era. Hatched areas had significant vaccination activity in 1999.
FIG. 3
FIG. 3
Worldwide incidence per 100,000 per year of all classical Hib diseases for children aged 0 to 4 years before the conjugate era. Hatched areas had significant vaccination activity in 1999. Note that nonbacteremic pneumonia, probably the most common Hib manifestation worldwide, is mostly neglected because very few reliable data are available.

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