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 2018
Between October and December 2018 (weeks 40 to 52), 23 cases of invasive H. influenzae were reported, bringing the total number of cases for 2018 to 82. This is comparable to annual cumulative case numbers reported over the previous ten years which ranged from 46 to 99 cases, as shown in Figure 1.
Of the 82 cases reported in 2018:
- Nine, which is 11%, were aged under five years
- three, which is 3.7%, were aged between 11 to 20 years
- ten, which is 12.2%, were aged between 21 to 40 years
- 60, which is 73.1%, were above 40 years of age
Information on clinical presentation was available for eight of the ten reported paediatric (under 16 years old) cases and included:
- respiratory symptoms
- gastro-intestinal symptoms
Of the 82 invasive cases reported in 2018:
- 74, which is 90.2%, had H. influenzae isolated from blood
- three, which is 3.7%, from cerebrospinal fluid
- five, which is 6.1%, from pleural fluid
Three cases are known to have died in 2018, which is slightly increased in comparison to annual figures over the previous five years (0 to 1 deaths per year).
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.
In 2018, H. influenzae type was available for 61 (74.4%) isolates, of which:
- 47, which is 77%, were non-typeable (NT)
- six, which is 9.8%, were type f
- two, which is 3.3%, were type a
- one, which is 1.6%, was type b
- five, which is 8.2%, were type e
H. influenzae type was available for seven of the ten paediatric cases:
- four were non-typeable
- two were type e
- one was type f
During this period, there has been a marked increase in the number of non-typeable (NT) isolates, although proportionally the percentage has remained stable from 2017 to 2018. Proportionally, there was a reduction in the number of cases for which typing was not available, from 36.4% in 2017 to 25.6% in 2018. Prior to 2016 (when one case was reported), laboratory confirmation of type a had not been recorded for any H. influenzae cases in Scotland, however in 2018 two type a cases were reported in older adults (over 60 years of age).
Vaccine Uptake Statistics
Vaccine uptake statistics can be found on the Information Services Division (ISD) website.