Pneumonia hospitalisation and case-fatality rates in older Australians with and without risk factors for pneumococcal disease: implications for vaccine policy.

S Dirmesropian,B Liu,J G Wood,S Karki,A T Newall,P Mcintyre,S Jayasinghe,C R Macintyre

doi:10.1017/s0950268818003473

Abstract

Community-acquired pneumonia (CAP) results in substantial numbers of hospitalisations and deaths in older adults. There are known lifestyle and medical risk factors for pneumococcal disease but the magnitude of the additional risk is not well quantified in Australia. We used a large population-based prospective cohort study of older adults in the state of New South Wales (45 and Up Study) linked to cause-specific hospitalisations, disease notifications and death registrations from 2006 to 2015. We estimated the age-specific incidence of CAP hospitalisation (ICD-10 J12-18), invasive pneumococcal disease (IPD) notification and presumptive non-invasive pneumococcal CAP hospitalisation (J13 + J18.1, excluding IPD), comparing those with at least one risk factor to those with no risk factors. The hospitalised case-fatality rate (CFR) included deaths in a 30-day window after hospitalisation. Among 266 951 participants followed for 1 850 000 person-years there were 8747 first hospitalisations for CAP, 157 IPD notifications and 305 non-invasive pneumococcal CAP hospitalisations. In persons 65-84 years, 54.7% had at least one identified risk factor, increasing to 57.0% in those ⩾85 years. The incidence of CAP hospitalisation in those ⩾65 years with at least one risk factor was twofold higher than in those without risk factors, 1091/100 000 (95% confidence interval (CI) 1060-1122) compared with 522/100 000 (95% CI 501-545) and IPD in equivalent groups was almost threefold higher (18.40/100 000 (95% CI 14.61-22.87) vs. 6.82/100 000 (95% CI 4.56-9.79)). The CFR increased with age but there were limited difference by risk status, except in those aged 45 to 64 years. Adults ⩾65 years with at least one risk factor have much higher rates of CAP and IPD suggesting that additional risk factor-based vaccination strategies may be cost-effective.

Highlights

Community-acquired pneumonia (CAP) is a frequent cause of hospitalisation in older adults with a substantial proportion of the burden caused by Streptococcus pneumoniae [1,2,3,4]
Individuals with these factors are classified as being at increased risk of pneumococcal disease in Australia and other countries [13, 14], the limited age-specific data on the relative incidence of CAP hospitalisation and mortality risk among such individuals makes it difficult to determine the merits of additional prevention targeted at high-risk groups
In the 65–74 year age group, the incidence of CAP hospitalisation was 563/100 000 (95% confidence interval (CI), 532–595) in those with at least one risk factor compared with 247/100 000 in those with no risk factors, a relative risks (RR) of 2.28

Summary

Introduction

Community-acquired pneumonia (CAP) is a frequent cause of hospitalisation in older adults with a substantial proportion of the burden caused by Streptococcus pneumoniae [1,2,3,4]. It is known that both CAP hospitalisation and mortality increase with age and with the presence of various comorbidities and risk behaviours [9, 10] including: heart disease, immunosuppressive treatment, asthma and diabetes, lung disease, alcoholism, cigarette smoking and excessive weight gain [8, 11, 12] Individuals with these factors are classified as being at increased risk of pneumococcal disease in Australia and other countries [13, 14], the limited age-specific data on the relative incidence of CAP hospitalisation and mortality risk among such individuals makes it difficult to determine the merits of additional prevention targeted at high-risk groups. There is a need to quantify the risk of pneumococcal CAP and IPD in high risk groups to help evaluate targeted vaccination strategies (e.g. potential use of PPV23 following PCV13 vaccination [16] in high-risk subgroups)

Methods

Results

Conclusion