What is the prevalence of Haemophilus influenzae infections?

Updated: Jun 11, 2021
  • Author: Joseph Adrian L Buensalido, MD; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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The Hib carriage rate is 2-4% in children aged 2-5 years, the age when children usually become colonized. Hib carriage rates are lowest in adults and infants and highest in preschoolers. Since the advent of conjugate Hib vaccine, the nasopharyngeal carrier rate has decreased (< 1% in vaccinated individuals). Only a small percentage of H influenzae carriers develop invasive disease. The frequency of Hib infections in patients with asplenia, splenectomy, sickle cell disease, malignancies, and congenital or acquired immunodeficiencies is higher than in individuals without these conditions. Unvaccinated infants younger than 12 months with a history of invasive disease have a higher risk of recurrence than vaccinated infants. [5]

In contrast, NTHi carriage rates can be as high as 70% or more. [6]

Currently, the incidence of Hib invasive diseases has greatly decreased in the United States because of the widespread of the Hib conjugate vaccine, while NTHi strains have become the most common cause of invasive disease in all age groups.

In countries outside the United States with established Hib immunization programs, such as England and Wales, NTHi is now the cause of nearly all invasive H influenzae diseases across all age groups. [2]

In Kamikawa subprefecture of Hokkaido, Japan, the incidence rate of H influenzae infection ranged from 15.1-36.3 per 100,000 population from 2006-2011. The Hib vaccine was introduced in November 2008, but vaccination rates rose to more than 90% only in December 2010, when Hib immunization became national policy. Thus, the rates dropped to 10.4 per 100,000 in 2012 and then to zero after 2013. No Hib meningitis cases have been reported since 2012, demonstrating the value of the vaccine in terms of case reduction. [7]

However, in many developing countries where Hib vaccination is not routine, invasive Hib disease is still a significant cause of morbidity and mortality.

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