Impact of pneumococcal polysaccharide vaccine on incidence and mortality after pneumonia in adults aged ≥60 years-a population-based retrospective cohort study

Mortality reduction with 23-valent pneumococcal polysaccharide vaccine: a systematic review and meta-analysis

BACKGROUND

Pneumococcal disease, caused by Streptococcus pneumoniae, imposes a significant global health burden, particularly affecting vulnerable groups such as the elderly and immunocompromised. The 23-valent pneumococcal polysaccharide vaccine (PPV23) is designed to protect against 23 serotypes of Streptococcus pneumoniae. However, there is ongoing debate about its effectiveness in reducing all-cause mortality. This systematic review and meta-analysis aimed to evaluate the efficacy of PPV23 in reducing all-cause and pneumonia-related mortality among adults.

METHODS

A systematic search was conducted across PubMed, Embase, and Web of Science, focusing on studies that evaluated the mortality outcomes of adults vaccinated with PPV23 compared to non-vaccinated adults. Both randomized controlled trials (RCTs) and observational studies were included, while case reports, case series, and non-human studies were excluded. Data extraction and quality assessment were facilitated by Nested Knowledge software, using the Newcastle-Ottawa Scale for observational studies and the Cochrane Risk of Bias tool for RCTs.

RESULTS

The search yielded 826 records, with 19 studies meeting the inclusion criteria. The pooled analysis of four RCTs showed no significant reduction in all-cause mortality (RR = 1.030; 95% CI: 0.945, 1.122). However, analysis of pneumonia-related mortality across various studies indicated a significant reduction (HR = 0.504; 95% CI: 0.316, 0.693). Moderate to high heterogeneity was noted in mortality studies, and a potential publication bias was identified.

CONCLUSION

The findings suggest that while PPV23 may not significantly reduce all-cause mortality, it is effective in reducing pneumonia-related mortality among adults, particularly in those at higher risk. These results support the continued use of PPV23 in targeted adult populations, emphasizing the need for more primary studies to explore its effectiveness across diverse groups.

Pneumococcal vaccination and primary care presentations for acute respiratory tract infection and antibiotic prescribing in older adults

BACKGROUND

While the 23-valent pneumococcal polysaccharide vaccine (PPV23) has demonstrated its role in preventing severe pneumococcal disease, its impact on more non-specific conditions like acute respiratory tract infection (ARI) and lower respiratory tract infections (LRTI) remains unclear. We aimed to investigate the role of PPV23 in prevention of presentations for ARI and LRTI and related antibiotic prescriptions among older adults in primary care.

METHODS

Using a nationwide general practice dataset, we followed a cohort of regularly attending patients aged ≥65 years from 1 January 2014 until 31 December 2018 for presentations for ARI, LRTI, and related antibiotic prescriptions. Associations between PPV23 receipt and each outcome were assessed using a multiple failures survival model to estimate hazard ratios (HR) adjusted for age, sex, socioeconomic status, and various health measures.

RESULTS

A cohort of 75,264 patients aged ≥65 years (mean 75.4, 56% female) in 2014 was followed. The incidence of presentations for ARI, ARI-related antibiotic prescription, LRTI, and LRTI-related antibiotic prescription was 157.6, 76.0, 49.6, and 24.3 per 1000 person-years, respectively. Recent PPV23 vaccine receipt was associated with a small reduction in ARI presentations (adjusted HR vaccinated vs. unvaccinated 0.96; 95%CI 0.94-0.98; p = 0.002); however, there was no reduction in ARI-related antibiotic prescription, LRTI presentation, nor LRTI-related antibiotic prescription (adjusted HR were 0.99[95%CI 0.96-1.03], 1.04[95%CI 0.99-1.09], 1.07[95%CI 1.00-1.14]).

CONCLUSION

PPV23 vaccination in older adults may result in a small reduction in the incidence of total ARI presentations in primary care. However, the effect is small and residual confounding cannot be excluded.

Pneumococcal Vaccine for Adults Aged ≥19 Years: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023

This report compiles and summarizes all published recommendations from CDC’s Advisory Committee on Immunization Practices (ACIP) for use of pneumococcal vaccines in adults aged ≥19 years in the United States. This report also includes updated and new clinical guidance for implementation from CDC

Before 2021, ACIP recommended 23-valent pneumococcal polysaccharide vaccine (PPSV23) alone (up to 2 doses), or both a single dose of 13-valent pneumococcal conjugate vaccine (PCV13) in combination with 1–3 doses of PPSV23 in series (PCV13 followed by PPSV23), for use in U.S. adults depending on age and underlying risk for pneumococcal disease. In 2021, two new pneumococcal conjugate vaccines (PCVs), a 15-valent and a 20-valent PCV (PCV15 and PCV20), were licensed for use in U.S. adults aged ≥18 years by the Food and Drug Administration

ACIP recommendations specify the use of either PCV20 alone or PCV15 in series with PPSV23 for all adults aged ≥65 years and for adults aged 19–64 years with certain underlying medical conditions or other risk factors who have not received a PCV or whose vaccination history is unknown. In addition, ACIP recommends use of either a single dose of PCV20 or ≥1 dose of PPSV23 for adults who have started their pneumococcal vaccine series with PCV13 but have not received all recommended PPSV23 doses. Shared clinical decision-making is recommended regarding use of a supplemental PCV20 dose for adults aged ≥65 years who have completed their recommended vaccine series with both PCV13 and PPSV23

Updated and new clinical guidance for implementation from CDC includes the recommendation for use of PCV15 or PCV20 for adults who have received PPSV23 but have not received any PCV dose. The report also includes clinical guidance for adults who have received 7-valent PCV (PCV7) only and adults who are hematopoietic stem cell transplant recipients

Distribution of serotypes causing invasive pneumococcal disease in older adults from high-income countries and impact of pediatric and adult vaccination policies

BACKGROUND

Neither indirect protection through use of 13-valent and 10-valent pneumococcal conjugate vaccines (PCV13 and PCV10) in pediatric National Immunization Programs (NIPs) nor direct vaccination with the 23-valent polysaccharide vaccine have eliminated vaccine serotype invasive pneumococcal disease (IPD) in older adults. Vaccinating older adults with higher-valency PCV15 and PCV20 could address remaining IPD due to pediatric PCV serotypes plus additional IPD due to serotypes included in these vaccines.

METHODS

We collected serotype-specific IPD data in older adults (≥65 years in most countries), from national or regional surveillance systems or hospital networks of 33 high-income countries. Data were from official government websites, online databases, surveillance system reports, published literature, and personal communication with in-country investigators. Average percentages of IPD serotypes were calculated.

RESULTS

Among 52,905 cases of IPD with a serotype identified, PCV13 serotypes accounted for 33.7% of IPD (55.8% and 30.6% for countries with PCV10 and PCV13 in the pediatric NIP), most commonly serotypes 3 (14.9%) and 19A (7.0%). PCV15 and PCV20 would cover an additional 10.4% and 32.9% of older adult IPD beyond PCV13 serotypes (PCV10 countries: 7.7% and 23.3%; PCV13 countries: 10.6% and 34.6%). The most common of these additional serotypes were 8 (9.9%), 22F (7.9%), 12F (4.6%), and 11A (3.3%). PPSV23 policies for older adults were not correlated with lower IPD percentages due to PPSV23 serotypes.

CONCLUSIONS

Vaccinating older adults with higher-valency PCVs, especially PCV20, could substantially reduce the remaining IPD burden in high-income countries, regardless of current PCV use in pediatric NIPs and adult PPSV23 policies.

Effect of the 23-valent pneumococcal polysaccharide vaccine on the incidence of hospitalisation with pneumonia in adults aged ≥65 years: retrospective cohort study using a population-based database in Japan

OBJECTIVES

The effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPV23) in preventing pneumonia in older adults remains controversial. Some studies have suggested differences in the effectiveness according to age or sex.

METHODS

We conducted an observational study using the database of vaccine subsidisation data and health insurance claims data for a city in Japan. Participants were residents from 2014 to 2018 turning 65, 70, 75, 80, 85, 90 or 95 years during a given fiscal year, and PPV23 during the first year of observation were identified. We matched vaccinated and non-vaccinated individuals of the same age using propensity scores for vaccination. Incidence of hospitalisation with pneumonia was compared using Fine-Gray regression model. We summarised the results for each age using random-effects meta-analysis and conducted a subgroup analysis by sex.

RESULTS

A total of 102,136 participants were included, of whom 35% received PPV23. Propensity score matching selected 32,510 pairs of vaccinated and non-vaccinated individuals. Overall, PPV23 administration was associated with a decreased incidence of hospitalisation with pneumonia (17.2 vs. 20.4 per 1,000 person-years, sub-distribution hazard ratio: 0.84, 95% confidence interval: 0.77 to 0.91). Vaccine effectiveness was highest among those aged 70 years and decreased with increasing age. No statistically significant effect was observed in those aged 90 or 95 years. Vaccine effectiveness was observed in both males and females.

CONCLUSIONS

PPV23 was associated with an overall decrease in hospitalisation with pneumonia in older adults. However, vaccine effectiveness was significant in those aged 65 to 85 years but not in older population.

Pneumococcal Vaccination in Adults: What Can We Learn From Observational Studies That Evaluated PCV13 and PPV23 Effectiveness in the Same Population?

INTRODUCTION

Fifteen and 20-valent pneumococcal conjugate vaccines (PCV15; PCV20) were recently licensed to prevent pneumococcal disease in adults. In the absence of efficacy or effectiveness data for these new vaccines, studies comparing 23-valent pneumococcal polysaccharide vaccine (PPV23) and PCV13 might help inform decision-making on how to best implement expanded-valency PCVs. Comparing PPV23 and PCV13 is problematic, as no head-to-head clinical trials evaluated efficacy. Comparing effectiveness results across observational studies that vary by population, design, and outcomes is difficult. To address these limitations, we undertook a narrative review of studies that assessed PPV23 and PCV13 vaccine effectiveness (VE) in the same adult populations.

METHODS

We conducted a literature search in PubMed and Google Scholar and screened 525 studies using a standardized evaluation framework.

RESULTS

Nine studies met inclusion criteria, all from high-income countries. None evaluated invasive pneumococcal disease (IPD) alone. VE against vaccine-type pneumococcal pneumonia ranged from 2 to 6% for PPV23 and 41 to 71% for PCV13. VE against pneumococcal pneumonia or severe pneumococcal disease (IPD or pneumococcal pneumonia) ranged from -10 to 11% for PPV23, 40 to 79% for PCV13, and 39 to 83% for sequential PCV13/PPV23. VE against all-cause pneumonia or lower respiratory tract infection ranged from -8 to 3% for PPV23 and 9 to 12% for PCV13.

CONCLUSIONS

Overall, PCV13 demonstrated better protection than PPV23 against pneumococcal disease and all-cause respiratory outcomes in the included studies. Where evaluated, sequential PCV13/PPV23 vaccination showed little benefit over PCV13 alone. Results support the use of PCVs to protect against pneumococcal disease and respiratory infections in adults.

Polysaccharide and conjugate vaccines to Streptococcus pneumoniae generate distinct humoral responses

Streptococcus pneumoniae is a major cause of community-acquired pneumonia, bacteremia, and meningitis in older adults worldwide. Two pneumococcal vaccines containing S. pneumoniae capsular polysaccharides are in current use: the polysaccharide vaccine PPSV23 and the glycoconjugate vaccine PCV13. In clinical trials, both vaccines elicit similar opsonophagocytic killing activity. In contrast to polysaccharide vaccines, conjugate vaccines have shown consistent efficacy against nasopharyngeal carriage and noninvasive pneumonia overall and for some prevalent individual serotypes. Given these different clinical profiles, it is crucial to understand the differential immunological responses induced by these two vaccines. Here, we used a high-throughput systems serology approach to profile the biophysical and functional features of serum antibodies induced by PCV13 and PPSV23 at 1 month and 1 year. In comparison with PPSV23, PCV13 induced higher titers across antibody isotypes; more durable antibody responses across immunoglobulin G (IgG), IgA, and IgM isotypes; and increased antigenic breadth. Although titers measured in opsonophagocytic activity (OPA) assays were similar between the two groups, confirming what was observed in clinical studies, serum samples from PCV13 vaccinees could induce additional non-OPA antibody-dependent functions, including monocyte phagocytosis and natural killer cell activation. In a multivariate modeling approach, distinct humoral profiles were demonstrated in each arm. Together, these results demonstrate that the glycoconjugate PCV13 vaccine induces an antigenically broader, more durable, polyfunctional antibody response. These findings may help explain the increased protection against S. pneumoniae colonization and noninvasive pneumonia and the longer duration of protection against invasive pneumococcal disease, mediated by PCV13.

Mortality changes for patients with pneumococcal pneumonia from 2012 to 2017 in Japan

INTRODUCTION

Pneumococcal pneumonia has a high morbidity and mortality in adults, especially those ≥65 years old. In the past decade, pneumococcal vaccination programs have been initiated worldwide, however, few data concerning mortality changes are available in pneumococcal pneumonia patients and there are no reports clarifying these current changes in Japan.

METHODS

Japanese patients ≥65 years old hospitalized with pneumococcal pneumonia between April 2012 and March 2018 were analyzed using the Diagnostic Procedure Combination database. In-hospital mortality was evaluated, and the odds ratios for this outcome in each fiscal year compared with that in 2012 was analyzed using multivariable logistic regression models.

RESULTS

Between 2012 and 2017, data of 47,375 pneumococcal pneumonia patients ≥65 years old were extracted. The incidence per 1000 person-years for in-hospital mortality was 60.4 in 2012, 56.8 in 2013, 63.2 in 2014, 56.1 in 2015, 73.0 in 2016, and 67.4 in 2017 and the odds ratios for in-hospital mortality in 2013, 2014, 2015, 2016, and 2017 compared with that in 2012 were 1.00, 1.05, 1.04, 1.06, and 0.98, respectively. There were no significant differences between 2012 and each year from 2013 to 2017. Low BMI; low ADL score; high A-DROP score; comorbid malignancy and heart failure; the coexistence of invasive pneumococcal infection; and the use of invasive mechanical ventilation were independent risk factors for in-hospital mortality.

CONCLUSIONS

There were no changes in in-hospital mortality in pneumococcal pneumonia patients between 2012 or each year from 2013 to 2017 and further epidemiological observations are necessary.

[Development and progress in respiratory tract infections]

The pandemic and the spread of multidrug-resistant pathogens impressively demonstrate that despite all medical and technical progress, infectious diseases still represent a global threat. The occurrence of new or difficult to treat infections due to resistance is determined by the dynamic evolution of pathogens, which can often have an erratic course and is not easily predictable. Coronavirus disease 2019 (COVID-19) has improved the understanding of airway infections and in addition to strategies targeted against the pathogen, has again demonstrated the importance of immunomodulation. Pathogen sequencing, point of care testing and decision aids based on artificial intelligence are some of the innovative techniques which will improve the management of airway infections in the coming years. In addition to viral airway infections, bacterial carbapenem-resistant pathogens (CRE) increasingly represent a therapeutic barrier in cases of nosocomial pneumonia. In recent years approval was given to beta lactams that are effective against CRE; however, their effectiveness is dependent on the underlying mechanism of resistance to carbapenem. An extended 20-valent pneumococcal conjugate vaccine will become available in 2022 for adults. A high-dose vaccine against influenza has been in use since 2021 for older adults. This article provides a highlighted overview of selected significant innovations in recent years in the field of airway infections.

[Pneumococcal vaccination]

Pneumokokken sind der häufigste bakterielle Erreger der ambulant erworbenen Pneumonie und gehören weltweit zu den häufigsten impfpräventablen Todesursachen. Es gibt einen Polysaccharidimpfstoff, der die Kapselpolysaccharide von 23 der über 90 bekannten Serotypen enthält, einen guten Schutz vor invasiven Pneumokokkeninfektionen vermittelt, aber T‑Zellen nicht stimuliert und damit kein immunologisches Gedächtnis hinterlässt. Bei Immunsupprimierten hat er eine eingeschränkte Wirksamkeit. Zunächst für Kleinkinder und später auch für Erwachsene wurde ein 13-valenter Konjugatimpfstoff zugelassen, der weniger Serotypen erfasst, aber ein immunologisches Gedächtnis hinterlässt und eine mukosale Immunität, d. h. die Eradikation gesunder Pneumokokkenträger und damit Herdenprotektionseffekte, vermittelt. Die STIKO empfiehlt derzeit bei verschiedenen Komorbiditäten sowie als Standardimpfung ab 60 Jahre die Indikationsimpfung mit PPV23, ggf. mit Wiederholungsimpfung nach frühestens 6 Jahren. Patienten mit Immunsuppression, chronischem Nierenversagen oder chronischer Leberinsuffizienz sollten wegen der eingeschränkten Wirksamkeit von PPV23 sowie einem hohen Risiko für Infektionen eine sequenzielle Impfung (zuerst PCV13, gefolgt von PPV23 nach 6 bis 12 Monaten) erhalten.

[Prevention by vaccination of adult patients with pulmonary diseases]

The key priority in patients with chronic lung diseases is currently immunization against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); all vaccines approved for this showed high effectiveness against severe infections. For patients with chronic pulmonary diseases the recommendations by the Standing Committee on Vaccination include not only the standard vaccinations in adulthood but also the so-called indication vaccinations. These include vaccinations against pneumococci and influenza. Advances include the recent development of new pneumococcal conjugate vaccines containing additional serotypes and the recommendation of a more effective high-dose vaccine against influenza for persons over 60 years old. With the next scheduled booster vaccination against tetanus and diphtheria a combination vaccine with pertussis antigen should be used. For patients with chronic lung disease the herpes zoster vaccine is recommended over the age of 50 years.

Effectiveness of a 23-valent pneumococcal polysaccharide vaccine for the prevention of pneumococcal pneumonia in the elderly with chronic respiratory diseases: a case-control study of a single center

Background

The effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPSV23) in preventing pneumococcal pneumonia has been controversial.

Methods

To evaluate the effectiveness of the PPSV23 in elderly outpatients with chronic respiratory diseases, we carried out a case–control study, including 4128 outpatients aged ≥ 65 years, in the respiratory department.

Results

There were 320 vaccinated patients, of which 164 were diagnosed with pneumococcal pneumonia. The adjusted odds ratio was 0.39 (95% confidence interval (CI), 0.17 to 0.89). In the subsets consisting of age groups ≥ 70 and ≥ 75 years, the adjusted odds ratio (95% CI) was respectively 0.16 (0.04 to 0.67) and 0.15 (0.02 to 1.12).

Conclusion

This real-world study suggests that PPSV23 can be useful in preventing pneumococcal pneumonia in the elderly with chronic respiratory diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01491-w.

Vaccines for older adults

The proportion of the global population aged 65 and older is rapidly increasing. Infections in this age group, most recently with SARS-CoV-2, cause substantial morbidity and mortality. Major improvements have been made in vaccines for older people, either through the addition of novel adjuvants-as in the new recombinant zoster vaccine and an adjuvanted influenza vaccine-or by increasing antigen concentration, as in influenza vaccines. In this article we review improvements in immunization for the three most important vaccine preventable diseases of aging. The recombinant zoster vaccine has an efficacy of 90% that is minimally affected by the age of the person being vaccinated and persists for more than four years. Increasing antigen dose or inclusion of adjuvant has improved the immunogenicity of influenza vaccines in older adults, although the relative effectiveness of the enhanced influenza vaccines and the durability of the immune response are the focus of ongoing clinical trials. Conjugate and polysaccharide pneumococcal vaccines have similar efficacy against invasive pneumococcal disease and pneumococcal pneumonia caused by vaccine serotypes in older adults. Their relative value varies by setting, depending on the prevalence of vaccine serotypes, largely related to conjugate vaccine coverage in children. Improved efficacy will increase public confidence and uptake of these vaccines. Co-administration of these vaccines is feasible and important for maximal uptake in older people. Development of new vaccine platforms has accelerated following the arrival of SARS-CoV-2, and will likely result in new vaccines against other pathogens in the future.

Age, Period and Cohort Analysis of Rates of Emergency Department Visits Due to Pneumonia in Taiwan, 1998-2012

BACKGROUND

Emergency room (ER) physicians need to face clinically suspected pneumonia patients in the front line of medical care and must do to give major medical interventions if patients show severity in pneumonia.

METHODS

The data of pneumonia-related ER visit rates were categorized based on the International Classification of Disease (ICD) Codes (480-486) between 1998 and 2012. We use an age-period-cohort (APC) model to separate the pneumonia-related ER visit rates to identify the effects of age, time period, and cohort for a total of 1,813,588 patients.

RESULTS

The age effect showed high risk for pediatric and elder populations. There is a significant increasing period effect, which increased from 1998 to 2012. The cohort effect tended to show an oscillation from 1913 to 1988 and the reverse in a recent cohort. Furthermore, the visit rate of pneumonia showed an increase from 1998 to 2012 for both genders.

CONCLUSION

Age is a risk factor for pneumonia-related ER visits, especially for children and adolescents and older patients. Period and cohort effects were also found to increase the pneumonia visit rates. An APC model used to provide an advance clue for trend of pneumonia-related ER visit rates diversified.

Impact of the 13-Valent Pneumococcal Conjugate Vaccine on the Incidence of All-cause Pneumonia in Adults Aged ≥60 Years: A Population-based, Retrospective Cohort Study

In this population-based study evaluating the effectiveness of the 13-valent pneumococcal conjugate vaccine (2012-2016) to prevent all-cause pneumonia in adults ≥60 years of age, we found significant, 0.63% absolute risk and 11.9% relative risk reductions on the 3-year (2014-2016) cumulative incidences of all-cause pneumonia after vaccination.

Impact of vaccination on invasive pneumococcal disease in Italy 2007-2017: surveillance challenges and epidemiological changes

Surveillance of new cases of invasive pneumococcal disease (IPD) in Italy was started in 2007 by the Ministry of Health (MoH). In 2012, pneumococcal childhood vaccination was introduced at the national level and, in 2017, for citizens aged 65 years and over. We describe here IPD epidemiology in Italy over the past 10 years investigating the impact of the vaccine programme on disease burden. Reports of IPD cases, data on serotype and vaccination coverage (VC) data were obtained from MoH annual reports, for the period 2007-2017. IPD notification rate and proportion by year, region, age and serotype were calculated. In 2007, 525 cases were reported (rate 0.88/100 000), rising to 1703 cases (rate 2.82/100 000) in 2017. The distribution of IPD cases by age group over time registered the largest share among individuals aged 65 years and over. A decreasing trend in notification rate was observed among those aged 0-4 years. During the same period, the 24-month VC increased, ranging from 80.9% to 96.7% in 2017. Molecular data indicated re-emergence of PPSV23-specific serotypes and non-vaccine serotypes. We observed an increase in IPD notifications during 2007-2017, likely due to an improved surveillance system, at least in some regions, with the relative quota of IPD notifications decreasing among vaccinated children cohorts. Further strengthening of IPD surveillance system, including molecular and vaccine coverage data, would be needed to assess and inform pneumococcal vaccination strategies in Italy.

A Systematic Review of Studies Published between 2016 and 2019 on the Effectiveness and Efficacy of Pneumococcal Vaccination on Pneumonia and Invasive Pneumococcal Disease in an Elderly Population

Adult vaccination is high on the agenda in many countries. Two different vaccines are available for the prevention of pneumococcal disease in adults: a 23-valent polysaccharide vaccine (PPV23), and a 13-valent conjugated vaccine (PCV13). The objective of this review is to update the evidence base for vaccine efficacy and effectiveness of PPV23 and PCV13 against invasive pneumococcal disease and pneumonia among an unselected elderly population. We systematically searched for clinical trials and observational studies published between January 1 2016 and April 17 2019 in Pubmed, Embase, Cinahl, Web of Science, Epistemonikos and Cochrane databases. Risk of bias was assessed using Cochrane Risk of Bias tool for and the Newcastle–Ottawa Scale. Results were stratified by vaccine type and outcome. We identified nine studies on PCV13 and six on PPV23. No new randomized clinical trials were identified. Due to different outcomes, it was not possible to do a meta-analysis. New high-quality observational studies indicate protective vaccine effectiveness for both vaccines against vaccine type pneumonia. Our estimates for the protective vaccine efficacy and effectiveness (VE) of PPV23 on pneumonia and pneumococcal pneumonia overlap with results from previously published reviews. Some of the results indicate that the effectiveness of the PPV23 is best in younger age groups, and that it decreases over time.

A model for predicting bacteremia in patients with community-acquired pneumococcal pneumonia: a retrospective observational study

Background

Pneumococcal pneumonia causes high morbidity and mortality among adults. This study aimed to identify risk factors for bacteremic pneumococcal pneumonia, and to construct a prediction model for the development of bacteremia in patients with community-acquired pneumococcal pneumonia.

Methods

We retrospectively analyzed data from patients hospitalized with community-acquired pneumococcal pneumonia between April 2007 and August 2015. Logistic regression models were applied to detect risk factors for pneumococcal bacteremia, and a receiver operating characteristic curve was used to devise a prediction model.

Results

Based on the results of sputum cultures, urine antigen tests, and/or blood cultures, 389 patients were diagnosed with pneumococcal pneumonia, 46 of whom had bacteremia. In the multivariate analysis, age < 65 years, serum albumin level < 3.0 g/dL, need for intensive respiratory or vasopressor support (IRVS), and C-reactive protein level > 20 mg/dL were identified as independent risk factors for the development of pneumococcal bacteremia. The bacteremia prediction score based on receiver operating characteristic curve analysis had a sensitivity of 0.74 and a specificity of 0.78 in patients with two risk factors. The area under the receiver operating characteristic curve was 0.77 (95% confidence interval (CI), 0.70–0.85).

Conclusions

Age < 65 years, hypoalbuminemia, IRVS, and high C-reactive protein level on admission are independent risk factors for the development of bacteremia in patients with community-acquired pneumococcal pneumonia. A prediction model based on these four risk factors could help to identify patients with community-acquired pneumococcal pneumonia at high risk of developing bacteremia; this can be used to guide antibiotic choices.

Trial registration

UMIN-CTR UMIN 000004353. Registered 7 October 2010. Retrospectively registered.