Clinical and Molecular Epidemiology of Childhood Invasive Nontypeable Haemophilus influenzae Disease in England and Wales

Abstract

The high level of genetic diversity in invasive NTHi strains highlights the difficulties in developing an effective vaccine against this pathogen.

Epidemiology of InvasiveHaemophilus influenzaeDisease, Europe, 2007–2014

“…Higher H. influenzae notification rates for infants, particularly neonates, the elderly, and women of childbearing age, were described before ( 30 , 31 ) and after ( 32 – 34 ) the introduction of routine Hib vaccination. In addition, several studies showed an increased burden of NTHi in groups more susceptible to infection, with high proportions of intensive care admission, high case-fatality rates, and frequent sequelae among survivors ( 2 , 29 , 32 , 35 ). The notification rate of NTHi cases in infants <1 month of age, with most cases presenting as septicemia, is particularly striking.…”

“…It is probable that the number of NTHi infections among neonates is underestimated ( 37 ), although the increasing notification rate among infants <1 month of age indicates that reporting may be improving. If developed, a vaccine against NTHi that could be administered to pregnant women could provide protection to expectant mothers and neonates ( 35 ). The genetic diversity of NTHi complicates vaccine development, but exploration into potential NTHi vaccine candidates is ongoing ( 38 ).…”

“…EU/EEA member states are not required to report all H. influenzae strains. Moreover, simply studying NTHi trends may now be insufficient for monitoring changes in the epidemiology of NTHi strains because they are more genetically diverse than encapsulated strains ( 29 , 35 , 37 , 39 ). Surveillance of NTHi in Europe may benefit from more genetic typing studies of circulating strains, with regard to carriage and disease, and the standardization of typing methodologies ( 24 , 36 , 37 ).…”

“…These trends may represent an actual increase in the incidence of disease, which could result from different factors, such as population aging and increased use of immunosuppressive therapy, both of which would increase the number of persons at risk for infection by these strains ( 17 , 35 ). Despite these increasing trends, we could not assess possible strain replacement resulting from the introduction of Hib vaccination because we could not compare serotype distributions or incidence between the prevaccination and postvaccination periods.…”

Polymicrobial bloodstream infection in an immunocompetent child

“…To the best of our knowledge, this is the first reported case of a bloodstream infection with S. pneumoniae and H. influenzae in a previously healthy child. Both bacterial pathogens are generally responsible for monomicrobic bloodstream infections, with severity varying from mild to fatal depending on the patient's history . We could not determine the reason for the two bacterial strains of bacteremia, but it is possible that both type 19A serotype S. pneumoniae and NTHi could be the pathogens involved, because the PCV7 vaccine covers only serotypes 4, 6B, 9V, 14, 18C, 19F, 23F, not including 19A, and Hib conjugate vaccine covers only serotype b.…”