Epidemiology, vaccine effectiveness, and risk factors for mortality for pneumococcal disease among hospitalised adults in Singapore: a case-control study

Abstract

Background: Streptococcus pneumoniae infections can lead to severe morbidity and mortality, especially in patients with invasive pneumococcal disease (IPD). This study evaluated factors associated with pneumococcal disease, pneumococcal vaccine effectiveness, and risk factors for all-cause mortality in hospitalised adults with pneumococcal disease in Singapore. Methods: Retrospective case-control study of patients tested for pneumococcal disease with streptococcal urinary antigen testing and at least one sterile site culture, during their admission to a tertiary hospital in Singapore from 2015 to 2017. Patients were defined as cases of IPD or non-IPD, or as controls, based on laboratory results and clinical diagnoses. Multivariable models were constructed to determine factors associated with IPD/non-IPD, and risk factors for mortality from pneumococcal disease. Vaccine effectiveness against IPD/non-IPD was estimated using a variation of the test-negative design. Results: We identified 496 pneumococcal disease cases, of whom 92 (18.5%) had IPD. The mean age of cases was 69.1 ± 15.4 years, and 65.5% were male. Compared with controls (N = 9181), IPD patients were younger (mean age 61.5 ± 16.3 years, vs 72.2 ± 16.1 years in controls; p < 0.001) and with less co-morbidities [median Charlson's score 1 (IQR 0-4), vs 3 (1-5) in controls; p < 0.001]. IPD patients also had the highest proportions with intensive care unit (ICU) admission (20.7%), inpatient mortality (26.1%) and longest median length of stay [9 (IQR 8-17) days]. On multivariable analysis, IPD was negatively associated with prior pneumococcal vaccination (adjusted relative risk ratio = 0.20, 95%CI 0.06-0.69; p = 0.011). Risk factors for mortality among pneumococcal disease patients were ICU admission, diagnosis of IPD, age ≥ 85 years and Charlson's score > 3. Conclusion: Patients with pneumococcal disease (especially IPD) were younger and had less co-morbidities than controls, but had higher risk of severe clinical outcomes and mortality. Pneumococcal vaccination effectiveness against IPD was estimated to be about 80%, and should be encouraged among high-risk patients.

Invasive pneumococcal disease, pneumococcal pneumonia and all-cause pneumonia in Hong Kong during the COVID-19 pandemic compared with the preceding 5 years: a retrospective observational study

“… 13 37 IPD can lead to significant mortality and morbidity. 44 Our study showed decrease in incidence and trend of IPD and were statistically significant. The decrease in mortality of IPD during the COVID-19 pandemic was statistically insignificant, which can be contributed by the relative small sample size.…”

Clinical Characteristics, Antimicrobial Resistance, and Outcomes of Patients with Invasive Pneumococcal Disease in Ningxia Hui Autonomous Region, China, 2013–2021

“…In this study, the median age of all patients was 31 years and the percent of patients between <16 years and 16–60 years groups are similar (40.16% vs 40.94%), while the percentage of patients older than 60 years old is low (18.9%). Many previous studies have described a higher level of pneumococcal disease among adult patients over the age of 65 and children younger than 5 years old [ 21 – 23 ]. This could be explained by the fact that our hospital is a comprehensive teaching hospital that houses various specialist wards to accept more adults with underlying diseases.…”

“…The minimum age of patients in this study is 1 day, however other studies reported the minimum age was 60 days or 6 months [ 24 , 25 ]. Underlying diseases have been reported as the risk factors for IPD [ 21 , 26 ], and reported underlying diseases including myocardial infarction, cerebrovascular disease, diabetes mellitus, malignancy, and so on. Our findings showed that 75 (59%) patients had some form of underlying diseases.…”

Strategies for pneumococcal vaccination in older adults in the coming era

“… 41 Furthermore, a case-control study found that the case fatality rate for IPD was 26.1%, in contrast to a 11.4% case fatality rate for noninvasive pneumococcal infections. 42 The recommendation of PPSV23 as the mainstay vaccine for IPD may also be significant. 5 Specifically, the inconsistent findings regarding its effectiveness against pneumococcal pneumonia may have contributed to the focus of IPD in recent studies.…”