At what age should one be concerned about Haemophilus influenzae (H. influenzae) type b infection?

From the Guidelines

Haemophilus influenzae type b infection is most concerning in children under 5 years old, particularly infants under 1 year, as well as in individuals with certain immunocompromising conditions, such as functional or anatomic asplenia, HIV infection, and immunoglobulin deficiency. For prevention, the Hib vaccine is crucial, and it's typically given as a series of shots at 2,4,6, and 12-15 months of age, as recommended by the Advisory Committee on Immunization Practices (ACIP) 1.

Key Points to Consider

• The majority of Hib disease in the United States occurs among unimmunized and underimmunized infants and children, as well as among infants too young to have completed the primary immunization series 1.
• Historically, American Indian/Alaska Native (AI/AN) populations have had higher rates of Hib disease and colonization than the general U.S. population, with a peak in disease at a younger age (4–6 months) than among other U.S. infant populations (6–7 months) 1.
• The Hib vaccine has been highly effective in reducing the incidence of invasive Hib disease in children aged <5 years in the United States, with a 99% decrease in annual incidence from 1989 to 2000 1.
• Certain high-risk groups, such as patients with functional or anatomic asplenia, HIV infection, and immunoglobulin deficiency, may require additional doses of Hib vaccine or revaccination after chemotherapy or radiation therapy 1.

Treatment and Prevention

• If infection occurs, prompt antibiotic treatment is essential, with common antibiotics used including amoxicillin-clavulanate, ceftriaxone, or cefotaxime, with dosage depending on age and severity.
• H. influenzae can cause serious illnesses like meningitis and pneumonia, especially in young children whose immune systems are still developing, and the bacteria spreads through respiratory droplets, making young children in close contact settings particularly vulnerable.
• While less common in older children and adults due to widespread vaccination, it's essential to stay vigilant, especially for those with compromised immunity or chronic conditions.

From the Research

Age of Concern for Haemophilus influenzae type b Infection

• Haemophilus influenzae type b (Hib) disease affects almost exclusively (95%) children aged less than 5 years throughout the world, with the mean age of onset being 6-24 months 2.
• Over 80% of cases in the pre-vaccine era occurred in children under five years of age 3.
• Children under 10 years of age who develop invasive Hib disease should receive rifampicin chemoprophylaxis to eliminate carriage and have Hib antibody levels tested around four weeks after infection 3.
• The World Health Organization (WHO) estimates that Hib is responsible for 3 million cases of serious illnesses and approximately 386,000 deaths worldwide each year in children aged under 5 years 2.

Vulnerable Age Groups

• Children under 10 years of age are considered vulnerable to Hib infection, particularly if they are immunosuppressed or have not been vaccinated 3, 2.
• Pre-school contacts of young children with invasive Hib disease are also at higher risk of developing secondary Hib infection 3.
• Household contacts of individuals who develop invasive Hib disease are at higher risk of developing secondary Hib infection themselves, particularly if the contact is a young child or is immunosuppressed 3.

Vaccination and Prevention

• Hib conjugate vaccines have been shown to be > 95% efficacious in diverse populations around the world and have dramatically reduced the incidence of invasive Hib disease across all age groups 2, 4.
• The introduction of Hib vaccines into national immunization programs has resulted in a significant decrease in the burden of Hib disease worldwide 5.
• Vaccination against Hib is recommended for all children, with the first dose typically administered at 2 months of age 6.