Haemophilus influenzae (H. influenzae) are bacteria commonly carried in the respiratory tract, which can cause acute invasive disease. They are divided into encapsulated and unencapsulated (non-typeable) strains. Encapsulated strains can be classified into six serotypes, from a to f, of which type b (Hib) was most prevalent prior to vaccine introduction. Infection with H. influenzae can cause the following conditions:
- acute respiratory infections
Less frequent conditions which may be caused by H. influenzae infection include:
- septic arthritis
For more information on H. influenzae, visit the NHS inform website.
Guidance on Haemophilus influenzae can be found below:
- For more information on Haemophilus influenzae type b (Hib) immunisation, including updates, please refer to the Public Health England (PHE) Green Book, Chapter 16.
- Find out about Public Health England's management of Hib.
- Training and educational materials for healthcare professionals are on the NHS Education for Scotland (NES) website.
For all infection prevention and control guidance visit the A-Z pathogens section of the National Infection and Prevention Control Manual.
Data and surveillance
In 1992, following introduction of the Hib vaccine for young children, the number of H. influenzae type b cases fell dramatically, not only in the vaccinated group but also in older age groups. Due to reduced carriage of the organism within the respiratory tract of vaccinated children, transmission to the wider community was effectively suppressed. The addition of the Hib booster vaccine in 2006, reduced case numbers further.
In Scotland, typing is conducted on all cases with positive laboratory reports for H. influenzae, in order that national trends in disease subtypes can be monitored. Further enhanced surveillance is carried out for all H. influenzae cases identified in children under the age of 5 and type b strains across all age groups.
Surveillance update for July to September 2019
Between July and September 2019 (weeks 27 to 39), 12 cases of invasive H. influenzae were reported, taking the total number of cases reported in the first three quarters of 2019 to 52. This is lower than the cumulative case numbers reported over the previous four years which ranged from 59 to 74 cases, as shown in Figure 1.
Of the 52 cases reported so far in 2019:
- three (5.8%) were aged under five years
- two (3.8%) were aged between 21 and 40 years
- 47 (90.4%) were over 40 years of age
Information on clinical presentation was available for all three paediatric (under 16 years old) cases. Two cases presented with bacteraemia, and one case presented with meningitis.
Of the 52 invasive cases reported so far in 2019:
- 46 (88.5%) had influenzae isolated from blood
- four (7.7%) from cerebrospinal fluid
- two (3.8%) from pleural fluid
One case is known to have died in 2019, which is comparable to the same period over the previous five years (0 to 2 deaths).
Figure 2 demonstrates the epidemiological impact of the Hib vaccine, for those aged under five (routinely vaccinated group) and for all ages (including under fives). Prevalence has shown a corresponding decrease in cases since 1992 and figures have remained relatively stable since 2011.
Figure 3 presents laboratory reports by serotype, since the introduction of the Hib booster campaign in 2003.
H. influenzae typing was carried out for 40 (76.9%) isolates, of which:
- 35 (87.5%) were non-typeable (NT)
- three (7.5%) were type f
- one (2.5%) was type b
- one (2.5%) was type a
All three paediatric cases were non-typeable.
There continues to be a high proportion of non-typeable (NT) isolates, and isolates not sent for typing.
Vaccine uptake statistics
Vaccine uptake statistics can be found on the Information Services Division (ISD) website.