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Updated: May 22, 2026
Assessing Respiratory Immune Responses to Haemophilus Influenzae
Published on: June 29, 2021
The burden of nonencapsulated Haemophilus influenzae in children and potential for prevention
Despoina Gkentzi1, Mary P E Slack, Shamez N Ladhani
1St. George's University of London, Cranmer Terrace, London, UK.
Insights
Nonencapsulated Haemophilus influenzae (ncHi) causes most invasive infections after Haemophilus influenzae serotype b (Hib) vaccination. A potential ncHi vaccine could prevent disease in vulnerable children, particularly neonates and those with comorbidities.
Area of Science:
- Microbiology
- Infectious Diseases
- Vaccinology
Background:
- Nonencapsulated Haemophilus influenzae (ncHi) is a growing cause of invasive disease, especially in neonates and immunocompromised children, following widespread Haemophilus influenzae serotype b (Hib) vaccination.
- ncHi infections present with higher case fatality rates compared to Hib infections and can manifest as sepsis or meningitis.
Purpose of the Study:
- To review the epidemiology and clinical features of invasive ncHi infections.
- To discuss the potential role of vaccines in preventing ncHi disease.
Main Methods:
- Literature review of invasive ncHi infections.
- Analysis of epidemiological data and clinical presentations.
Main Results:
- Invasive ncHi disease incidence peaks in the first month of life, with premature neonates being particularly vulnerable.
- Comorbidities such as neurological disease, malignancy, and immunosuppression are common in older children with invasive ncHi.
- Meningitis is a significant presentation, occurring in at least a quarter of invasive ncHi cases.
Conclusions:
- A vaccine targeting ncHi could offer crucial protection for high-risk pediatric populations, including neonates and children with comorbidities.
- Further research is needed to identify specific risk factors for neonatal and childhood ncHi disease and to understand long-term outcomes of meningitis.
Purpose Of Review:
In countries with established Haemophilus influenzae serotype b (Hib) immunization programmes, nonencapsulated H. influenzae (ncHi) is responsible for most invasive H. influenzae infections across all age groups and is associated with higher case fatality. A pneumococcal conjugate vaccine has recently been licensed, which may potentially also protect against invasive H. influenzae infections.
Recent Findings:
Invasive ncHi disease is uncommon in childhood but has a much higher incidence in the first month of life. Most neonates with invasive ncHi infections are born prematurely and develop septicaemia in the first 48 h of life which can be fatal. After this period, invasive ncHi incidence falls rapidly and remains low throughout childhood. Most infants and children who develop invasive ncHi disease have significant underlying comorbidities, particularly neurological disease, malignancy and other conditions requiring immunosuppressive therapy. Although characteristically associated with respiratory tract infections, at least a quarter of invasive ncHi infections present with meningitis.
Summary:
A vaccine against ncHi could have an important preventive role in children with comorbidities. Future studies should focus on assessing specific risk factors for neonatal and childhood ncHi disease and long-term outcomes of children with invasive ncHi meningitis.
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