Invasive haemophilus influenza disease

The major disease burden of invasive H. influenzae infection occurs in children under five years (Fogarty, 1995). The most harmful complication is bacteraemia, which is accompanied by a focal infection such as meningitis, pneumonia, or cellulitis in 30–50% of cases (Devarajan, 2009).

Risk of complications

Meningitis is the principal clinical presentation of invasive disease, but bone and joint infections, pneumonia, epiglottitis, cellulitis and septicaemia can also occur. Skin and soft tissue infections may occur in around 6% of patients, followed by a limited number of sequelae (Otero Reigada, 2005). Only the invasive forms are considered as health states in the model.

To estimate the risk of meningitis we used the surveillance data reported in the ECDC Invasive Disease Surveillance report on clinical presentations of the acute symptomatic disease (ECDC, 2013a; ECDC, 2013b). Reported data indicates that meningitis and septicaemia occur together in 0–1% of cases, whereas meningitis alone occurs in 15–18% (15% in 2010, 18% in 2011) of cases, resulting in an overall risk of 15–18% of developing meningitis. The risk of developing meningitis during the acute phase of the disease is age-specific. Age and gender-specific data were extracted from ECDC’s TESSy database on the meningitis complications of IHID for 2010 and 2011 (see Table 4). The risk of developing the long-term sequelae is age and gender-specific.

Long-term sequelae

Bacterial meningitis may cause long-term sequelae and permanent disabilities. To investigate this we extracted the risk of developing these complications after meningitis episodes from Edmond et al. (Edmond, 2010).

Meningitis accounts for various long-term sequelae (each of which is multiplied by the risk of developing meningitis during the acute phase of the disease: 15–18%): cognitive difficulties (0.17–0.20%), seizure disorders (0.23–0.27%), hearing loss (0.48–0.58%), motor deficit (0.33–0.40%), visual disturbance (0.08–0.09%), behavioural problems (0.32–0.38%), clinical impairments (0.18–0.22%) and multiple impairments (0.39–0.47%) (Edmond, 2010).

Case fatality proportion

The parameters for the case fatality proportion were based on data for EU/EEA countries in 2011, see Table 3 (ECDC, 2013).

Model input summary

Table 1. Transition probabilities used in the outcome tree

Health outcome
(Health state)

Distribution of health states in health outcome

Transition probability

Source/assumption

Hearing loss

 

0.48-0.58%

Edmond, 2010

Cognitive difficulties

 

0.17-0.20%

Edmond, 2010

Seizure disorder

 

0.23-0.27%

Edmond, 2010

Motor deficit

 

0.33-0.40%

Edmond, 2010

Visual disturbance

 

0.08-0.09%

Edmond, 2010

Behavioural problems

 

0.32-0.38%

Edmond, 2010

Clinical impairments

 

0.18-0.22%

Edmond, 2010

Multiple impairments

 

0.39-0.47%

Edmond, 2010

Fatal cases  due to symptomatic infection

 

See Table 3 (5.4-19.5%)

ECDC, 2013

Table 2. Disability weights and duration

Health outcome
(Health state)

Disability Weight (DW) (Haagsma, 2015)

Duration

DW

Label

In years

Source

Symptomatic infection

0.655 (0.579-0.727)

Intensive care unit admission

0.019

Tunkel, 2004 Assuming the duration of antimicrobial therapy

Permanent disability following meningitis

 

 

Remaining life expectancy

 

1. Hearing loss

0.008-0.103

From lowest to highest hearing loss related DWs

 

 

2. Cognitive difficulties

0.044-0.188

From lowest to highest intellectual disability related DWs

 

 

3. Seizure disorder

0.07 (0.057-0.088)

Generic uncomplicated disease: worry and daily medication

 

 

4. Motor deficit

0.011-0.421

From lowest to highest motor impairment related DWs

 

 

5. Visual disturbance

0.004-0.171

From lowest to highest vision impairment related DWs

 

 

6. Behavioural problems

0.088 (0.07-0.108)

Subacute sclerosing panencephalitis – phase 1 (assuming best fitting health state description)

 

 

7. Clinical impairments

0.004-0.421

From lowest to highest DW included in this model

 

 

8. Multiple impairments

0.004-0.421

From lowest to highest DW included in this model

 

 

Table 3. CFR following symptomatic infection

Age

 CFR

0

19.5%

1-4

6.5%

5-14

5.7%

15-64

5.4%

≥65

15%

Table 4. Age specific distribution per gender of the 15-18% risk of developing meningitis manifestation during the symptomatic infection (TESSy 2010-2011)

Age
group

%

F

M

0

15.69

17.12

01-04

15.69

18.49

05-09

2.61

5.48

10-14

1.31

2.74

15-19

1.31

2.74

20-24

2.61

4.11

25-29

0.00

0.00

30-34

3.27

1.37

35-39

1.96

4.79

40-44

3.92

7.53

45-49

3.92

8.22

50-54

7.19

2.74

55-59

7.19

2.74

60-64

3.27

4.79

65-69

10.46

3.42

70-74

11.11

5.48

75-79

5.23

4.11

80-84

2.61

1.37

85+

0.65

2.74

Total

100

100

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