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What is Haemophilus Influenza Type B (HIB)?


What is Haemophilus Influenzae Type B (Hib)

Haemophilus influenzae (H. influenzae) is a small gram-negative coccobacillus1 found only in humans2 and can be either encapsulated (typeable) or unencapsulated (nontypeable). Typeable H. influenzae contain a polysaccharide capsule and are identified and labeled with letters a through f.  Strains that do not have a polysaccharide capsule are referred to as nontypeable. Current H. influenzae vaccines target only H. influenzae type b, which was believed to be the cause of 95 percent of all H. influenzae infections in the pre-vaccine era.3 Hib infections are more likely to occur between September and December and again between March and May. 4

H. influenzae type b (Hib) is transmitted by direct contact with respiratory secretions and enters the body through the upper respiratory tract. While uncommon, H. influenzae type b and other types of H. influenzae infections can also be transmitted through the birth canal, from an infected mother, to her newborn baby.5 6 In most cases, Hib can remain in the mouth and nose for up to several months, without causing illness.7 If Hib, however, enters the bloodstream, it becomes invasive, resulting in serious infections that include meningitis, pneumonia, bacteremia, epiglottis, cellulitis, septic arthritis, osteomyelitis, otitis media, pericarditis, and endocarditis.8

A diagnosis of H. influenzae, including H. influenzae type b, is made by the laboratory testing of bodily fluids such as blood and spinal fluid.9

Prior to the introduction of the Hib vaccine in the mid-1980’s, H. influenzae type b was responsible for between 50 to 65 percent of meningitis cases, a serious infection of the membranes that cover the spinal cord and brain, which is the most common clinical presentation of invasive disease.10 Before Hib vaccines became available, infections occurred nearly exclusively in children under the age of 5, with the majority of infections occurring in children younger than eighteen months11 and Navajo and Native Alaskan Americans were noted to have higher rates of the disease.12 H. influenzae invasive disease did not become a nationally notifiable disease until 1991,13 six years after the first Hib vaccines became available for use in the United States.14 Since the introduction of Hib vaccines, Hib meningitis has become more common in adults than in children.15 While the CDC reports a nearly 99 percent decrease in Hib invasive disease among children 5 years of age and younger, 16 adults, especially seniors over the age of 65, have become more susceptible to the infection. 17 18 A 2011 published study on H. influenzae infections in Utah found that between 1998 and 2008, over 50 percent of H. influenzae infections and 67 percent of H. influenzae related deaths occurred in adults over the age of 65. 19

While invasive disease caused by H. influenzae type b (Hib) has decreased, invasive disease by non-b and nontypeable H. influenzae have increased.20 21 22 23 24 25 26 27 28 29 Non-b type infections, such as H. influenzae type a, can cause invasive disease with complications similar to Hib 30 and nontypeable H. influenzae invasive illness, while most commonly associated with infections such as conjunctivitis, otitis media, sinusitis, and pneumonia, still has the potential to cause serious invasive H. influenzae disease.31 Hib vaccines target only H. influenzae type b and offers no protection against any other type of H. influenzae infection.32

IMPORTANT NOTE: NVIC encourages you to become fully informed about Haemophilus Influenzae Type B (Hib) and the Hib vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.

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References

1 CDC Haemophilus influenzae type b – Haemophilus influenzae Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015.

2 CDC Haemophilus influenzae type b – Epidemiology Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015.

3 CDC Haemophilus influenzae type b – Haemophilus influenzae Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015.

4 CDC Haemophilus influenzae type b – Epidemiology Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015.

5 Supram HS,  Gokhale S, Bhatta DR, et al. Haemophilus influenzae type B genital infection and septicemia in pregnant woman: a case report Asian Pac J Trop Dis. 2014 Jun; 4(3): 207–209.

6 Rathore MH Pediatric Haemophilus Influenzae Infection - Pathophysiology Medscape Apr. 4, 2016

7 CDC Haemophilus influenzae type b – Pathogenesis Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015.

8 CDC Haemophilus influenzae type b - Clinical Features Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015.

9 CDC Haemophilus influenzae Disease (including Hib) Diagnosis, Treatment, and Complications. Feb. 13, 2018

10 Ibid

11 CDC Haemophilus influenzae type b  Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015.

12 Rathore MH Pediatric Haemophilus Influenzae Infection - Epidemiology Medscape Apr. 4, 2016

13 CDC Haemophilus influenzae type b - Secular Trends in the United States Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book). 13th ed. 2015.

14 CDC MMWR. Morbidity and mortality weekly report` MMWR Apr. 19, 1985; 34 (15); 201-205

15 Rathore MH Pediatric Haemophilus Influenzae Infection - Pathophysiology Medscape Apr. 4, 2016

16 CDC Haemophilus influenzae Disease (Including Hib) For Clinicians – Trends Feb. 13, 2018

17 Rubach MP, Bender JM, Mottice S et al. Increasing Incidence of Invasive Haemophilus influenzae Disease in Adults, Utah, USA Emerg Infect Dis. 2011 Sep; 17(9): 1645–1650.

18 Blain A,  MacNeil J, Wang X, et al. Invasive Haemophilus influenzae Disease in Adults ≥65 Years, United States, 2011 Open Forum Infect Dis. 2014 Sep; 1(2): ofu044.

19 Rubach MP, Bender JM, Mottice S et al. Increasing Incidence of Invasive Haemophilus influenzae Disease in Adults, Utah, USA Emerg Infect Dis. 2011 Sep; 17(9): 1645–1650.

20 Bender JM, Cox CM, Mottice S, et al. Invasive Haemophilus influenzae disease in Utah children: an 11-year population-based study in the era of conjugate vaccine. Clin Infect Dis. 2010 Apr 1;50(7):e41-6

21 Waggoner-Fountain LA, Hendley JO, Cody EJ et al. The emergence of Haemophilus influenzae types e and f as significant pathogens. Clin Infect Dis. 1995 Nov;21(5):1322-4.

22 Rubach MP, Bender JM, Mottice S et al. Increasing Incidence of Invasive Haemophilus influenzae Disease in Adults, Utah, USA Emerg Infect Dis. 2011 Sep; 17(9): 1645–1650.

23 McConnell A, Tan B, Scheifele D, et al. Invasive infections caused by haemophilus influenzae serotypes in twelve Canadian IMPACT centers, 1996-2001. Pediatr Infect Dis J. 2007 Nov;26(11):1025-31.

24 Urwin G, Krohn JA, Deaver-Robinson K et al. Invasive disease due to Haemophilus influenzae serotype f: clinical and epidemiologic characteristics in the H. influenzae serotype b vaccine era. The Haemophilus influenzae Study Group. Clin Infect Dis. 1996 Jun;22(6):1069-76.

25 Ulanova M, Tsang RSW Haemophilus influenzae serotype a as a cause of serious invasive infections. Lancet Infect Dis. 2014 Jan;14(1):70-82

26 Bruce MG, Deeks SL, Zulz T et al. Epidemiology of Haemophilus influenzae serotype a, North American Arctic, 2000-2005. Emerg Infect Dis. 2008 Jan;14(1):48-55.

27 Adam HJ, Richardson SE, Jamieson FB et al. Changing epidemiology of invasive Haemophilus influenzae in Ontario, Canada: evidence for herd effects and strain replacement due to Hib vaccination. Vaccine. 2010 May 28;28(24):4073-8

28 Langere JD, de Jonge MI Invasive Disease Caused by Nontypeable Haemophilus influenzae Emerg Infect Dis. 2015 Oct; 21(10): 1711–1718.

29 Cerquetti M, Giufrè M Why we need a vaccine for non-typeable Haemophilus influenzae. Hum Vaccin Immunother. 2016 Sep; 12(9): 2357–2361.

30 Rathore MH Pediatric Haemophilus Influenzae Infection - Pathophysiology Medscape Apr. 4, 2016

31 Murphy TF, Faden H, Bakaletz LO, et al. Nontypeable Haemophilus influenzae as a pathogen in children. Pediatr Infect Dis J. 2009 Jan;28(1):43-8

32 CDC Haemophilus influenzae Disease (including Hib) – Prevention. Feb. 13, 2018


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