Haemophilus influenzae
Haemophilus influenzae serotype B
Before the implementation of vaccines in the mid-1990s that targeted Hib, this serotype accounted for over 90% of infections. Its high virulence is a result of its additional protective layer (capsular polysaccharide) that ‘shields’ the deeper bacterial structures from the hosts' immune system.
Burden of disease due to Hib
- In the pre-vaccine era, Hib was responsible for causing severe invasive infections that included meningitis, pneumonia in children 5 years and under.
- By 1990, most cases of meningitis were attributed to Hib although meningitis can also be caused by three other bacterial species: Streptococcus pneumoniae, Neisseria meningitidis, Streptococcus agalactiae.
- Before the widespread introduction of Hib vaccines in 2000, Haemophilus influenzae was responsible for 8.13 million related diseases and 371 000 deaths amongst children aged 1-59 months.
Risk Population
- In the pre-vaccine era, approximately 85% of Hib disease occurred in children aged from 0 to 4 years with the peak incidence age being 6 to 12 months. Hib disease can also affect older adults and immunocompromised individuals.
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Hib asymptomatic nasopharyngeal carriage rates range from 7 to 15% in children from high-risk populations e.g native Americans or African populations.
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