Epidemiology of community-acquired pneumonia in the era of extended serotype-covering multivalent pneumococcal conjugate vaccines

Recommendations for Adult Immunization by the Korean Society of Infectious Diseases, 2023: Minor Revisions to the 3rd Edition

The Korean Society of Infectious Diseases has been regularly developing guidelines for adult immunization since 2007. In 2023, the guidelines for the following seven vaccines were revised: influenza, herpes zoster, pneumococcal, tetanus-diphtheria-pertussis (Tdap), human papillomavirus (HPV), meningococcal, and rabies vaccines. For the influenza vaccine, a recommendation for enhanced vaccines for the elderly was added. For the herpes zoster vaccine, a recommendation for the recombinant zoster vaccine was added. For the pneumococcal vaccine, the current status of the 15-valent pneumococcal conjugate vaccine and 20-valent PCV was described. For the Tdap vaccine, the possibility of using Tdap instead of tetanus-diphtheria vaccine was described. For the HPV vaccine, the expansion of the eligible age for vaccination was described. For the meningococcal vaccine, a recommendation for the meningococcal B vaccine was added. For the rabies vaccine, the number of pre-exposure prophylaxis doses was changed. This manuscript documents the summary and rationale of the revisions for the seven vaccines. For the vaccines not mentioned in this manuscript, the recommendations in the 3rd edition of the Vaccinations for Adults textbook shall remain in effect.

Prior pneumococcal vaccination improves in-hospital mortality among elderly population hospitalized due to community-acquired pneumonia

BACKGROUND

Pneumococcal vaccination is a preventive method to reduce pneumonia related mortality. However, real-world data on efficacy of the pneumococcal vaccine in reducing mortality is lacking, especially in elderly patients. This study was conducted to assess the effects of prior pneumococcal vaccination in elderly pneumonia patients.

METHODS

The data was procured from the Health Insurance Review and Assessment and Quality Assessment database. Hospitalized patients who met the criteria of community-acquired pneumonia (CAP) were included and they were grouped according to vaccination state. Patients were aged ≥ 65 years and treated with beta-lactam, quinolone, or macrolide. Patients were excluded when treatment outcomes were unknown.

RESULTS

A total of 4515 patients were evaluated, and 1609 (35.6%) of them were vaccinated prior to hospitalization. Mean age was 77.0 [71.0;82.0], 54.2% of them were male, and mean Charlson comorbidity index (CCI) was 3.0. The patients in the vaccinated group were younger than those in the unvaccinated group (76.0 vs. 78.0 years; P < 0.001), and showed higher in-hospital improvement (97.6 vs. 95.0%; P < 0.001) and lower 30-day mortality (2.6 vs. 5.3%; P < 0.001). After adjusting confounding factors such as age, gender, CURB score and CCI score, the vaccinated group demonstrated a significant reduction in 30-day mortality (hazard ratio [HR] 0.58, 95% confidence interval [CI] 0.41-0.81; P < 0.01) and in-hospital mortality (HR 0.53, 95% CI0.37-0.78; P < 0.001) compared to the unvaccinated group in multivariate analysis. Vaccinated group showed better 30-day survival than those in non-vaccinated group (log-rank test < 0.05).

CONCLUSIONS

Among elderly hospitalized CAP patients, prior pneumococcal vaccination was associated with improved in-hospital mortality and 30-day mortality.

Cost-effectiveness of the 20-valent pneumococcal conjugate vaccine versus the 23-valent pneumococcal polysaccharide vaccine for older adults in South Korea

BACKGROUND

Despite the demonstrated immunogenicity and safety of the 20-valent pneumococcal conjugate vaccine (PCV20) in older adults, the cost-effectiveness of the PCV20 was not examined compared to the 23-valent pneumococcal polysaccharide vaccine (PPSV23) in South Korea. Therefore, this study aimed to evaluate the cost-effectiveness of PCV20 compared with PPSV23 in adults aged 65 years and older in South Korea.

METHODS

We constructed a Markov model that included susceptible states, invasive pneumococcal disease (IPD), non-bacteremic pneumonia (NBP), and death. The population was categorized by disease risk status (low risk, moderate risk, and high risk) and age group (65-74/75-84/85-99 years) at model entry. The annual incidence and mortality of IPD and NBP associated with PCV20 and PPSV23 were estimated based on serotype coverage, vaccine coverage, and vaccine effectiveness. The disease costs and utilities were obtained from previous studies. The incremental cost-effectiveness ratio (ICER) was used to evaluate cost-effectiveness within the threshold of 16,824 USD per quality-adjusted life-year (QALY).

RESULTS

Among the total population (n = 8,843,072), PCV20 prevented 1941 and 50,575 cases of IPDs and NBPs, respectively, and 898 and 8593 deaths due to IPDs and NBPs compared to PPSV23. The total medical cost per person was 12.11 USD higher in PCV20, with a gain of 0.0053 LYs and 0.0045 QALYs per person. The ICER for PCV20 and PPSV23 was 2270 USD/LY and 2677 USD/QALY.

CONCLUSIONS

In South Korea, PCV20 is a cost-effective option compared with PPSV23 for adults aged 65 years and older. These cost-effectiveness results provide evidence for decision-making regarding the approval and National Immunization Program implementation of PCV20.

Epidemiology of Pneumococcal Pneumonia in Louisville, Kentucky, and Its Estimated Burden of Disease in the United States

Streptococcus pneumoniae remains a primary pathogen in hospitalized patients with community-acquired pneumonia (CAP). The objective of this study was to define the epidemiology of pneumococcal pneumonia in Louisville, Kentucky, and to estimate the burden of pneumococcal pneumonia in the United States (US). This study was nested in a prospective population-based cohort study of all adult residents in Louisville, Kentucky, who were hospitalized with CAP from 1 June 2014 to 31 May 2016. In hospitalized patients with CAP, urinary antigen detection of 24 S. pneumoniae serotypes (UAD-24) was performed. The annual population-based pneumococcal pneumonia incidence was calculated. The distribution of S. pneumoniae serotypes was characterized. Ecological associations between pneumococcal pneumonia and income level, race, and age were defined. Mortality was evaluated during hospitalization and at 30 days, 6 months, and 1 year after hospitalization. Among the 5402 CAP patients with a UAD-24 test performed, 708 (13%) patients had pneumococcal pneumonia. The annual cumulative incidence was 93 pneumococcal pneumonia hospitalizations per 100,000 adults (95% CI = 91-95), corresponding to an estimated 226,696 annual pneumococcal pneumonia hospitalizations in the US. The most frequent serotypes were 19A (12%), 3 (11%), and 22F (11%). Clusters of cases were found in areas with low incomes and a higher proportion of Black or African American population. Pneumococcal pneumonia mortality was 3.7% during hospitalization, 8.2% at 30 days, 17.6% at 6 months, and 25.4% at 1 year after hospitalization. The burden of pneumococcal pneumonia in the US remains significant, with an estimate of more than 225,000 adults hospitalized annually, and approximately 1 out of 4 hospitalized adult patients dies within 1 year after hospitalization.

Community-Acquired Pneumococcal Pneumonia in Highly Vaccinated Population: Analysis by Serotypes, Vaccination Status, and Underlying Medical Conditions

BACKGROUND

Targeted risk population has been highly vaccinated against pneumococcal diseases in South Korea. Despite this, the pneumococcal serotype distribution is evolving, which impedes efficient roll-out of vaccines.

METHODS

This prospective cohort study included patients aged ≥ 19 years with community-acquired pneumonia (CAP) from five university hospitals in South Korea between September 2018 and July 2021. The outcomes of interest were the demographic and clinical characteristics of patients with CAP, pneumococcal serotype distribution, and risk factors of 30-day mortality in patients with pneumococcal CAP (pCAP). Considering the high seroprevalence, we analyzed the clinical characteristics of serotype 3 pCAP.

RESULTS

A total of 5,009 patients hospitalized with CAP was included (mean age ± standard deviation, 70.3 ± 16.0 years; 3,159 [63.1%] men). Streptococcus pneumoniae was the leading causative agent of CAP (11.8% overall, 17.7% in individuals aged < 65 years with chronic medical conditions). Among the 280 serotyped Streptococcus pneumococcus, serotype 3 was the most common (10.0%), followed by serotypes 19A (8.9%), 34 (8.9%), and 35B (8.9%). Non-vaccine serotypes (serotype 35B [13.9%] and 34 [12.0%]) were the most prevalent in 108 individuals vaccinated with 23-valent pneumococcal polysaccharide vaccine (PPSV23). Serotype 3 was prevalent, irrespective of PPSV23 vaccination status, and more common in individuals with chronic lung disease (P = 0.008). Advanced age (adjusted odds ratio [aOR], 1.040; 95% confidence interval [CI], 1.011-1.071), long-term care facility residence (aOR, 2.161; 95% CI, 1.071-4.357), and bacteremia (aOR, 4.193; 95% CI, 1.604-10.962) were independent risk factors for 30-day mortality in patients with pCAP. PPSV23 vaccination reduced the risk of mortality (aOR, 0.507; 95% CI, 0.267-0.961).

CONCLUSION

Serotype 3 and 19A were still the most common serotypes of pCAP in South Korea despite the national immunization program of 13-valent pneumococcal conjugated vaccine in children and PPSV23 in old adults. PPSV23 vaccination might reduce the risk of mortality in patients with pCAP.

Outcomes and Predictors of Severe Community-acquired Pneumonia Among Adults Admitted to the University of Gondar Comprehensive Specialized Hospital: A Prospective Follow-up Study

Background

Severe community-acquired pneumonia is a common life-threatening infection with a high rate of unfavorable outcome. This study aimed to assess the outcomes and predictors of hospitalized severe community-acquired pneumonia patients at University of Gondar comprehensive specialized hospital.

Methods

A prospective follow-up study was conducted at University of Gondar comprehensive specialized hospital from May 1 to September 31, 2021. The data was collected by reviewing patients' charts and interviewing the patients themselves. Descriptive statistics, binary and multivariable logistic regression analysis were performed accordingly. Variables with p-value <0.2 on binary logistic regression were analyzed using multivariable logistic regression and variables with p<0.05 were considered to have significant association.

Results

A total of 239 admitted patients with severe community-acquired pneumonia were enrolled in the study. An unfavorable outcome was observed in 105 (44%) patients; 24.27% was in-hospital all-cause mortality, 12.5% was nonresolution, 5.8% was complicated cases, and 1.26% were gone against medical care for poor prognosis. After analyzing multivariable logistic regression, confusion (OR= 4.84; 95%CI: 1.47-15.88), anemia (OR= 2.36; 95%CI: 1.01-5.52), leukopenia (OR=4.38; 95%CI: 1.26-15.25), leukocytosis (OR=3.15; 95%CI: 1.23-7.96), elevated creatinine (OR=5.67; 95%CI: 1.72-18.65), intubation (OR=7.27; 95%CI: 1.58-33.37) and antibiotic revision during treatment for a different reason (OR=0.02; 95%CI: 0.01-0.07) were variables significantly associated with unfavorable outcome.

Conclusion

Unfavorable outcome was high among hospitalized severe community acquired pneumonia patients, and confusion, elevated creatinine, anemia, leukopenia, leukocytosis, intubation during admission, and antibiotic revision during the course were independent predictors associated significantly with the unfavorable outcome. It is important to consider the development of a treatment protocol for the hospital and to further research incorporating the microbiologic profile of the patients.

Targeted Transcriptomic Screen of Pneumococcal Genes Expressed during Murine and Human Infection

The advent of pneumococcal conjugate vaccines led to the near disappearance of most of the included serotypes in high-income settings but also the rise of nonvaccine-type colonization and disease. Alternative strategies, using genetically conserved proteins as antigens, have been evaluated preclinically and clinically for years, so far unsuccessfully. One possible explanation for the failure of these efforts is that the choice of antigens may not have been sufficiently guided by an understanding of the gene expression pattern in the context of infection. Here, we present a targeted transcriptomic analysis of 160 pneumococcal genes encoding bacterial surface-exposed proteins in mouse models, human colonization, and human meningitis. We present the overlap of these different transcriptomic profiles. We identify two bacterial genes that are highly expressed in the context of mouse and human infection: SP_0282, an IID component of a mannose phosphotransferase system (PTS), and SP_1739, encoding RNase Y. We show that these two proteins can confer protection against pneumococcal nasopharyngeal colonization and intraperitoneal challenge in a murine model and generate opsonophagocytic antibodies. This study emphasizes and confirms the importance of studies of pneumococcal gene expression of bacterial surface proteins during human infection and colonization and may pave the way for the selection of a protein-based vaccine candidate.

Risk factor-based analysis of community-acquired pneumonia, healthcare-associated pneumonia and hospital-acquired pneumonia: Microbiological distribution, antibiotic resistance, and clinical outcomes

BACKGROUND

Healthcare-associated pneumonia (HCAP) lies in the intersection of community-acquired pneumonia (CAP) and hospital-acquired pneumonia (HAP). Although HCAP is excluded from the revised HAP guideline, reassessment for HCAP is needed considering its heterogeneous characteristics.

METHODS

The microbiological distribution, antibiotic resistance, and clinical outcomes in CAP, HCAP, and HAP were studied retrospectively. The susceptibility to standard CAP regimens (β-lactams plus macrolide or fluoroquinolone monotherapy) and rates of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (P. aeruginosa) infections were evaluated in the CAP group and HCAP subgroups.

RESULTS

In total, 933 cases were included (CAP, n = 557; HCAP, n = 264; HAP, n = 112). In the CAP and HCAP cases, Streptococcus pneumoniae (7.4% vs. 5.7%) and P. aeruginosa (9.2% vs. 18.6%) were the most common gram-positive and gram-negative pathogens. Staphylococcus aureus (methicillin-resistant, 2.7%; methicillin-susceptible, 2.4%) and carbapenem-resistant Acinetobacter baumannii (20.5%) were the most common Gram-positive and Gram-negative pathogens in the HAP group, respectively. Higher susceptibility to levofloxacin was observed in CAP and HCAP isolates than that to β-lactam agents. However, levofloxacin non-susceptibility was significantly higher in long-term care facility (LTCF)-onset HCAP compared to community-onset HCAP (43.6% vs. 22.7%, P = 0.014).

CONCLUSION

HCAP showed higher rates of P. aeruginosa and MRSA infections than CAP. Empirical antipseudomonal therapy should be considered in the treatment of HCAP. Prior isolation of P. aeruginosa was the most important risk factor for P. aeruginosa infection.

Molecular Characterization of Predominant Serotypes, Drug Resistance, and Virulence Genes of Streptococcus pneumoniae Isolates From East China

Streptococcus pneumoniae is a common diplococcus pathogen found worldwide. The characterization of predominant serotypes, drug resistance, and virulence genes of S. pneumoniae isolates prevailing in different areas and countries is clinically important for choice of antibiotics and improvement of vaccines. In this study, pneumonia (78.7%) and meningitis (37.0%) were the predominant diseases observed in the 282 (children) and 27 (adults) S. pneumoniae-infected patients (p < 0.05) from seven hospitals in different areas of East China. Of the 309 pneumococcal isolates, 90.3% were classified by PCR into 15 serotypes, with serotypes 19F (27.2%) and the 6A/B (19.1%) being most predominant (p < 0.05). Importantly, serotypes 15A and 15B/C combined for a total of 10.4% of the isolates, but these serotypes are not included in the 13-valent pneumococcal capsule conjugate vaccine used in China. Antimicrobial susceptibility analysis by the E-test showed that >95% of the 309 pneumococcal isolates were susceptible to moxifloxacin and levofloxacin, as well as 18.4, 85.8, and 81.6% of the isolates displayed susceptibility to penicillin, cefotaxime, and imipenem, respectively. A significant correlation between the prevalence of predominant serotypes and their penicillin resistance was observed (p < 0.05). In particular, >95% of all the pneumococcal isolates showed resistance to erythromycin and azithromycin. Of the nine detected virulence genes, the lytA, ply, hysA, and nanA were the most common with 95–100% positive rates in the 309 pneumococcal isolates, while the pavA and psaA genes displayed a significant correlation with pneumococcal bacteremia and meningitis (p < 0.05). Overall, our data suggested that the predominant serotypes, drug resistance, and virulence genes of the S. pneumoniae isolates prevailing in East China are distinct from those observed in other areas of China and adjacent countries.

Effectiveness of Pneumococcal Vaccination Against Hospitalized Pneumococcal Pneumonia in Older Adults: A Prospective, Test-Negative Study

BACKGROUND

Despite use of the 13-valent pneumococcal conjugate vaccine (PCV13) and 23-valent pneumococcal polysaccharide vaccine (PPSV23) over the last decade, the disease burden of pneumococcal pneumonia is still high. We evaluated the field effectiveness of PCV13, PPSV23, and sequential vaccination against pneumococcal pneumonia in older adults.

METHODS

This prospective multicenter study was conducted in adults aged ≥ 65 years with hospitalized community-acquired pneumonia (CAP) between September 2015 and August 2017. The case-control test-negative design was used to estimate vaccine effectiveness (VE) against pneumococcal CAP.

RESULTS

Of 1,525 cases with hospitalized CAP, 167 (11.0%) were identified as pneumococcal CAP. In the elderly aged ≥65 years, the adjusted VE of pneumococcal vaccines against pneumococcal CAP was statistically insignificant: 40.0% (95% CI -10.8% to 67.5%) for PCV13 and 11.0% (95% CI, -26.4% to 37.3%) for PPSV23. However, in the younger subgroup (aged 65-74 years), sequential PCV13/PPSV23 vaccination showed the highest adjusted VE of 80.3% (95% CI 15.9% to 95.4%), followed by single-dose PCV13 (adjusted VE 66.4%; 95% CI 0.8% to 88.6%) and PPSV23 (adjusted VE 18.5%; 95% CI -38.6% to 52.0%).

CONCLUSIONS

Sequential PCV13/PPSV23 vaccination is most effective for preventing pneumococcal CAP among the elderly aged 65-74 years.