The burden of nonencapsulated Haemophilus influenzae in children and potential for prevention

Abstract

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.