Pediatric complicated pneumonia and pneumococcal serotype replacement: trends in hospitalized children pre and post introduction of routine vaccination with Pneumococcal Conjugate Vaccine (PCV7)

Complicated pneumococcal pneumonia in the era of higher-valent pneumococcal conjugate vaccines: a systematic literature review and meta-analysis, 2001-2022

PURPOSE

To estimate pneumococcal conjugate vaccine (PCV) national program impact on pneumococcal complicated pneumonia (PnCP) based on changes in PnCP population-based incidence, PnCP proportion of all-cause complicated pneumonia (or invasive pneumococcal disease), and PnCP serotype distribution.

METHODS

MEDLINE, EMBASE, and Global Index Medicus articles (2001-March 2022) reporting laboratory-confirmed PnCP studies were stratified by age group, outcome measure, PCV program period(s) (pre-PCV, transition, and post-PCV), serotype distribution (based on serotyping methodology used), and PCV serotype formulation. Random effect meta-analysis of the total number of serotyped isolates within each study was used to calculate pooled serotype-specific percentages.

RESULTS

Of 1360 publications screened, the 134 studies included from 30 countries differed widely by methodological approaches. Pediatric PnCP incidence tended to decline from pre-PCV to post-PCV periods, as did PnCP as a proportion of all-cause complicated pneumonia from transition to post-PCV periods. Studies describing changes in serotype distribution by PCV program period applied detection methods that varied from pre-PCV period microbiological culture with Quellung serotyping to in the transition and post-PCV periods molecular methods like PCR. Meta-analysis revealed near elimination of pediatric PCV7-serotype PnCP between pre- and post-PCV, while the PCV13nonPCV7 percentage increased from 51.1% pre-PCV period to 76.5% in the transition period, remaining stable post-PCV period. Non-PCV13 serotypes increased slightly from low baseline numbers. Adult data were lacking or inconsistent.

CONCLUSIONS

Although studies were heterogeneous, pediatric PnCP incidence and proportion tended to decline from pre-PCV to post-PCV periods, and PCV13nonPCV7 serotype distribution percentage remained unchanged from transition to post-PCV period. Standardization of PnCP surveillance methods, definitions, and reporting is needed to evaluate accurately PCV program impact.

Epidemiological characteristics and serotype distribution of culture-confirmed pediatric pneumococcal pneumonia before and after PCV 10 introduction, a multicenter study in Bogota, Colombia, 2008-2019

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) have decreased pneumonia in children. Colombia introduced mass vaccination with PCV10 in 2012.

METHODS

Cases of pneumococcal pneumonia from 10 hospitals were included. Two periods were compared: pre-PCV10: 2008-2011 and post-PCV10: 2014-2019. The objective was to compare epidemiological and clinical characteristics before and after PCV10 vaccination.

RESULTS

A total of 370 cases were included. Serotypes 1 (15, 11.2%) and 14 (33, 24.6%) were the most frequent in the pre-PCV10 period, with only 4 (3%) cases of serotype 19A and 1 case (0.7%) serotype 3. From the pre-PCV10 period to the post-PCV10 period, cases of serotypes 1 (6, 3.1%) and 14 (1, 7.8%) decreased, while cases of serotypes 19A (58, 30.2%), serotype 3 (32, 16.7%) and 6A (7, 3.6%) increased (p < 0.001); complicated pneumonia (CP) increased significantly (13.4% to 31.8%) (p < 0.001); hospitalizations increased from 8 (5.5-15) to 12 (7-22) days (p < 0.001); and the frequency of PICU admission increased from 32.8% to 51.6% (p = 0.001). The use of ampicillin-sulbactam (0.7% to 24%) and ceftriaxone/clindamycin (0.7% to 5.7%) increased in the post-PCV10 period. The duration of empirical antibiotic treatment was 7 (4-11) days in the pre-PCV10 period and increased to 10 (6-17) days (p < 0.001) in the post-PCV10 period. Lethality showed a slight nonsignificant increase (7.5% vs. 9.9%; p = 0.57) in the post-PCV10 period.

CONCLUSIONS

PCV10 significantly decreased cases of serotypes 1 and 14, with an increase in cases of serotypes 19A, 3 and 6A, which were the predominant serotypes and had greater severity (e.g., admission to the PICU, CP and more resistance, with an increase in the use of broad-spectrum antibiotics and longer hospitalization) and subsequently included in PCV13. Current data support national and regional evidence on the importance of replacing PCV10 with a higher valence that includes 19A, such as PCV13, with the aim of reducing circulation, particularly of this serotype.

Characterization of the Anti-Inflammatory Capacity of IL-10-Producing Neutrophils in Response to Streptococcus pneumoniae Infection

Neutrophils are immune cells classically defined as pro-inflammatory effector cells. However, current accumulated evidence indicates that neutrophils have more versatile immune-modulating properties. During acute lung infection with Streptococcus pneumoniae in mice, interleukin-10 (IL-10) production is required to temper an excessive lung injury and to improve survival, yet the cellular source of IL-10 and the immunomodulatory role of neutrophils during S. pneumoniae infection remain unknown. Here we show that neutrophils are the main myeloid cells that produce IL-10 in the lungs during the first 48 h of infection. Importantly, in vitro assays with bone-marrow derived neutrophils confirmed that IL-10 can be induced by these cells by the direct recognition of pneumococcal antigens. In vivo, we identified the recruitment of two neutrophil subpopulations in the lungs following infection, which exhibited clear morphological differences and a distinctive profile of IL-10 production at 48 h post-infection. Furthermore, adoptive transfer of neutrophils from WT mice into IL-10 knockout mice (Il10^-/-) fully restored IL-10 production in the lungs and reduced lung histopathology. These results suggest that IL-10 production by neutrophils induced by S. pneumoniae limits lung injury and is important to mediate an effective immune response required for host survival.

Molecular epidemiology of Streptococcus pneumoniae isolated from pediatric community-acquired pneumonia in pre-conjugate vaccine era in Western China

BACKGROUND

Streptococcus pneumoniae (S. pneumoniae) is one of the most common pathogens which can cause morbidity and mortality in pediatric infections worldwide. This study aimed to describe the phenotypic and molecular characteristics of community-acquired pneumonia (CAP)-causing S. pneumoniae recovered from children in Western China.

METHODS

We retrospectively enrolled pediatric patients younger than 5 years diagnosed with CAP. All 419 S. pneumoniae isolates were tested for antibiotic susceptibility, serotypes, virulence genes, resistance genes, and sequence types. The potential relationships between molecular characteristics were tested by correspondence analysis.

RESULTS

Most of S. pneumoniae isolates were resistant to erythromycin, tetracycline, clindamycin and trimethoprim-sulfamethoxazole, with 93.8% isolates classified as multidrug resistant. The dominant STs were ST271 (30.8%) and ST320 (12.2%), while the prevailing serotypes were 19F (46.8%), 6B (11.5%), 23F (9.5%) and 19A (9.3%). The coverage rates of PCV-7 and PCV-13 were 73.03% and 86.16%, while the coverage rates of PCV13 among children aged < 1 year and 1-2 years were high in 93.18% and 93.62%. We also observed that CC271 expressed more of mef (A/E), lytA, rlrA and sipA than non-CC271 isolates. Moreover, there were strong corresponding relationships between molecular characteristics.

CONCLUSIONS

The high coverage rate of PCV13 suggests the necessity of introducing the PCV13 vaccine in Western China. Our findings underscore the value of monitoring multiple molecular characteristics to provide new guidance for developing future pneumococcal vaccines.

The Modified Surface Killing Assay Distinguishes between Protective and Nonprotective Antibodies to PspA

The most important finding of this study is that the MSKA can be used as an in vitro functional assay. Such an assay will be critical for the development of PspA-containing vaccines. The other important findings relate to the locations and nature of the protection-eliciting epitopes of PspA. There are limited prior data on the locations of protection-eliciting PspA epitopes, but those data along with the data presented here make it clear that there is not a single epitope or domain of PspA that can elicit protective antibody and there exists at least one region of the αHD which seldom elicits protective antibody. Moreover, these data, in concert with prior data, strongly make the case that protective epitopes in the αHD are highly conformational (≥100-amino-acid fragments of the αHD are required), whereas at least some protection-eliciting epitopes in the proline-rich domain are encoded by ≤15-amino-acid sequences.

Pneumococcal surface protein A (PspA) elicits antibody protective against lethal challenge by Streptococcus pneumoniae and is a candidate noncapsular antigen for inclusion in vaccines. Evaluation of immunity to PspA in human trials would be greatly facilitated by an in vitro functional assay able to distinguish protective from nonprotective antibodies to PspA. Mouse monoclonal antibodies (MAbs) to PspA can mediate killing by human granulocytes in the modified surface killing assay (MSKA). To determine if the MSKA can distinguish between protective and nonprotective MAbs, we examined seven MAbs to PspA. All bound recombinant PspA, as detected by enzyme-linked immunosorbent assay and Western blotting; four gave strong passive protection against fatal challenge, two were nonprotective, and the seventh one only delayed death. The four that were able to provide strong passive protection were also most able to enhance killing in the MSKA, the two that were not protective in mice were not effective in the MSKA, and the MAb that was only weakly protective in mice was weakly effective in the MSKA (P < 0.001). One of the four most protective MAbs tested reacted to the proline-rich domain of PspA. Two of the other most protective MAbs and the weakly protective MAb reacted with a fragment from PspA’s α-helical domain (αHD), containing amino acids (aa) 148 to 247 from the N terminus of PspA. The fourth highly protective MAb recognized none of the overlapping 81- or 100-aa fragments of PspA. The two nonprotective MAbs recognized a more N-terminal αHD fragment (aa 48 to 147).

IMPORTANCE The most important finding of this study is that the MSKA can be used as an in vitro functional assay. Such an assay will be critical for the development of PspA-containing vaccines. The other important findings relate to the locations and nature of the protection-eliciting epitopes of PspA. There are limited prior data on the locations of protection-eliciting PspA epitopes, but those data along with the data presented here make it clear that there is not a single epitope or domain of PspA that can elicit protective antibody and there exists at least one region of the αHD which seldom elicits protective antibody. Moreover, these data, in concert with prior data, strongly make the case that protective epitopes in the αHD are highly conformational (≥100-amino-acid fragments of the αHD are required), whereas at least some protection-eliciting epitopes in the proline-rich domain are encoded by ≤15-amino-acid sequences.

Pneumococcal conjugate vaccines decrease community-acquired alveolar pneumonia with and without pleural effusion in children <60 months in Southern Israel, 2002-2016

Background: Radiographically-proven community-acquired alveolar pneumonia with pleural effusion (PE-CAP) has a less favourable outcome than pneumonia without pleural effusion (NPE-CAP). We assessed PE-CAP and NPE-CAP rate dynamics in children <60 months in southern Israel before and after 7- and 13-valent pneumococcal conjugate vaccine (PCV7/PCV13) implementation (2002-2016).Methods: An ongoing, prospective observational study. Our hospital serves a captive population of ∼75,000 children <60 months, enabling incidence calculation. PCV7/PCV13 were implemented in Israel in July 2009/November 2010, respectively. All chest radiographs (CXRs) were digitalized and analysed according to the WHO Standardization of Interpretation. Annual incidences of PE-CAP and NPE-CAP were calculated, 2002-2016. Incidence-rate ratios (IRRs) comparing PCV13 (2013-2016), PCV7 (2010-2011) and pre-PCV (2002-2008) periods were calculated.Results: Overall, 12,271 CAP episodes were identified; 159 (1.3%) PE-CAP and 12,112 (98.7%) NPE-CAP. In total, 65.8% and 34.2% were children <24 and 24-59 months, respectively; 61.0% and 39.0% were Bedouin and Jewish children, respectively. Following PCV7 introduction, PE-CAP rates declined by 48% (Incidence rate ratios [IRR] = 0.52; 0.26-1.03), while NPE-CAP rates declined by 20% (IRR = 0.80; 0.75-0.86). In the PCV13 period, PE-CAP and NPE-CAP rates further declined, resulting in overall 70% (IRR = 0.30; 0.18-0.50) and 55% (IRR = 0.45; 0.43-0.48) reductions, respectively, comparing the PCV13 and the pre-PCV periods. Similar trends were observed in all subgroups (Bedouin vs. Jewish and age < 24 months vs. 24-59 months).Conclusions: Following PCV7/PCV13 introduction, PE-CAP and NPE-CAP rates substantially declined. However, the rate dynamics were different, with steeper declines observed in PE-CAP rates, possibly deriving from differences in disease aetiology.

The Impact of Pneumococcal Vaccination on Bacterial and Viral Pneumonia in Western Australian Children: Record Linkage Cohort Study of 469589 Births, 1996-2012

Background

Pneumococcal conjugate vaccine (PCV) was included in Australia's National Immunisation Program for all children from 2005. We assessed the impact of PCV on all-cause and pathogen-specific pneumonia hospitalizations in Western Australian (WA) children aged ≤16 years.

Methods

All hospitalizations with pneumonia-related International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification diagnosis codes occurring in WA-born children (1996-2012) were linked to pathology records. Age-specific incidence rate ratios and temporal trends for all-cause and pathogen-specific pneumonia hospitalizations were calculated before and after PCV introduction.

Results

Among 469589 births, there were 15175 pneumonia-related hospitalizations. Hospitalization rates were 6.7 (95% confidence interval, 6.4-6.9) times higher in Aboriginal than in non-Aboriginal children. Following PCV introduction, all-cause pneumonia hospitalizations showed significant declines across all age groups. A pathogen was identified in 2785 of 6693 (41.6%) pneumonia hospitalizations that linked to a pathology record. Respiratory syncytial virus (RSV) was most frequently identified, with RSV-associated pneumonia hospitalization rates of 89.6/100000 child-years in Aboriginal and 26.6/100000 child-years in non-Aboriginal children. The most common bacterial pathogen was Streptococcus pneumoniae in Aboriginal children (32.9/100000 child-years) and Mycoplasma pneumoniae in non-Aboriginal children (8.4/100000 child-years). Viral pneumonia rates declined in all children following PCV introduction, with the greatest declines seen in non-Aboriginal children; declines in bacterial pneumonia were observed in non-Aboriginal children.

Conclusions

Based on our ecological analyses, PCV seems to have had an impact on hospitalizations for pneumonia, suggesting that the pneumococcus is likely to play a role in both bacterial and viral pneumonia. Respiratory viruses remain an important pathogen in childhood pneumonia. Vaccines targeting respiratory viruses are needed to combat the residual burden of childhood pneumonia.

Trends in Pediatric Complicated Pneumonia in an Ontario Local Health Integration Network

Following the introduction of 7-valent pneumococcal vaccine (PCV7), while overall rates of invasive pneumococcal disease and pneumococcal pneumonia in children declined, rates of empyema increased. We examined changes in the incidence of hospitalization for pediatric complicated pneumonia (PCOMP) in Eastern Ontario, Canada, particularly since the introduction of the 13-valent vaccine (PCV13). A retrospective chart review was carried out evaluating previously healthy children admitted with PCOMP, which included empyema, parapneumonic effusion, necrotizing pneumonia, and lung abscess between 2002 and 2015. Three-hundred seventy-one children were included. Subjects had a median age of four years, and 188/370 (50.8%) required a chest tube. Admission rates changed markedly during this time period. The number of admissions per year rose most sharply between 2009 and 2012, corresponding to the period following introduction of PCV7 and then the occurrence of pandemic influenza A (H1N1). In children who likely received PCV13, the incidence of PCOMP returned to approximately pre-PCV7 levels. In contrast, rates of PCOMP in older children (who would not have received PCV13) remained elevated during the post-PCV13 time period. While rates of PCOMP, particularly in older children, remain elevated following the introduction of PCV13, this might be expected to resolve with more widespread vaccine coverage with PCV13 and herd immunity.

Staphylococcus aureus and Streptococcus pneumoniae interaction and response to pneumococcal vaccination: Myth or reality?

S. aureus and S. pneumoniae are both common pathogens that are also carried by a large proportion of healthy individuals in the nasal and nasopharyngeal spaces. A negative association between carriage of S. aureus and S. pneumoniae has been reported in children in various epidemiologic studies from different geographical regions. Most studies found that the negative association between S. pneumoniae and S. aureus was significant only for carriage of vaccine-type S. pneumoniae strains. In this review, we summarize the various suggested mechanisms of this suggested bacterial interference, and the clinical implications reported following PCV introduction to date in various geographical regions.

Discovery of Immunodominant B Cell Epitopes within Surface Pneumococcal Virulence Proteins in Pediatric Patients with Invasive Pneumococcal Disease

The identification of immunodominant B cell epitopes within surface pneumococcal virulence proteins in pediatric patients with invasive pneumococcal disease (IPD) is a valuable approach to define novel vaccine candidates. To this aim, we evaluated sera from children with IPD and age-matched controls against 141 20-mer synthetic peptides covering the entire sequence of major antigenic fragments within pneumococcal virulence proteins; namely, choline-binding protein D (CbpD), pneumococcal histidine triad proteins (PhtD and PhtE), pneumococcal surface protein A (PspA), plasminogen and fibronectin binding protein B (PfbB), and zinc metalloproteinase B (ZmpB). Ten immunodominant B cell epitopes were identified: CbpD-pep4 (amino acids (aa) 291-310), PhtD-pep11 (aa 88-107), PhtD-pep17 (aa 172-191), PhtD-pep19 (aa 200-219), PhtE-pep32 (aa 300-319), PhtE-pep40 (aa 79-98), PfbB-pep76 (aa 180-199), PfbB-pep79 (aa 222-241), PfbB-pep90 (aa 484-503), and ZmpB-pep125 (aa 431-450). All epitopes were highly conserved among different pneumococcal serotypes, and four of them were located within the functional zinc-binding domain of the histidine triad proteins PhtD and PhtE. Peptides CbpD-pep4, PhtD-pep19, and PhtE-pep40 were broadly recognized by IPD patient sera with prevalences of 96.4%, 92.9%, and 71.4%, respectively, whereas control sera exhibited only minor reactivities (<10.7%). Their specificities for IPD were 93.3%, 95%, and 96.7%; their sensitivities were 96.4%, 92.9%, and 71.4% and their positivity likelihood ratios for IPD were 14.5, 18.6, and 21.4, respectively. Furthermore, purified antibodies against CbpD-pep4, PhtD-pep19, and PhtE-pep40 readily bound on the surfaces of different pneumococcal serotypes, as assessed by FACS and immunofluorescence analysis. The identified immunodominant B cell epitopes provide a better understanding of immune response in IPD and are worth evaluation in additional studies as potential vaccine candidates.

Effectiveness of 7-valent pneumococcal conjugate vaccine: A meta-analysis of post-marketing studies

AIM: To investigate the 7-valent pneumococcal conjugate vaccine (PCV7) effectiveness.

METHODS: A systematic literature review of studies which evaluated the effectiveness of PCV7 vaccine was performed searching the keyword “heptavalent pneumococcal conjugate vaccine” in PubMed and Scopus until March 16, 2013. The selection of potential eligible articles was done by two researchers independently on the basis of abstract and title and only post-marketing studies were included in the systematic review. Data extraction was carried out by two researchers with respect to invasive pneumococcal diseases due to both all and vaccine serotypes in pre-vaccine and post-vaccine periods in children less than 5 years. Results of studies which were considered suitable for meta-analysis were combined by means of relative risk (RR) with 95%CI. Vaccine effectiveness was calculated as (1-RR) × 100. Heterogeneity was assessed by I² and a random effects model was used to combine data in the case of heterogeneity. RevMan 5 was used to pool data.

RESULTS: On the whole, 757 eligible papers were identified from the literature search in PubMed and Scopus. Of them, 62 were finally considered in the systematic review and 38 were included in the meta-analysis. In all post-marketing studies included in the systematic review the incidence of invasive pneumococcal diseases due to vaccine serotypes declined significantly with the exception of few studies showing stability or a slight, but not significant, increase. Furthermore most of studies highlighted also a reduction in the incidence of invasive pneumococcal diseases due to all serotypes. With regards to meta-analysis, a random effects model was used to combine data because of the high heterogeneity. Data combination showed that the effectiveness of PCV7 in reducing invasive pneumococcal diseases due to vaccine serotypes and to all serotypes was 84% (95%CI: 74%-90%) and 53% (95%CI: 46%-59%) respectively. These results are confirmatory with respect to the efficacy of PCV7 against invasive pneumococcal diseases due to vaccine serotypes.

CONCLUSION: PCV7 implementation determines a significant decrease of invasive pneumococcal diseases.

Treatment trends and outcomes in US hospital stays of children with empyema

BACKGROUND

Recently published practice guidelines continue to reflect uncertainty about the comparative effectiveness of various treatments for empyema in children. We describe treatment trends and outcomes in pediatric empyema using the most current nationally representative data.

METHODS

Using survey methods and Kids' Inpatient Databases from 1997 to 2009, we evaluated hospital stays in children 0-18 years of age. We used 2009 data to compare transfer-out rates and lengths of stay across various types of treatment, after adjusting for patient and hospital factors.

RESULTS

From 1997 to 2009, empyema discharges steadily increased from 3.1 to 6.0 per 100,000 children (P < 0.001 for trend) and also were increasingly likely (P < 0.01) to be coded for: (1) at least 1 pleural drainage procedure (76.4-83.2%), (2) multiple drainage procedures (36.0-41.6%) and (3) home health care (8.7-15.0%). By 2009, video-assisted thoracoscopic surgery was more commonly coded than chest tube drainage and was associated with a lower transfer-out rate (0.6% vs. 10.1%, adjusted P < 0.001) but no reduction in mean length of stay [11.2 vs. 13.4 days, adjusted incidence rate ratio 0.95 (95% confidence interval: 0.88-1.04)] for children neither admitted nor discharged by transfer.

CONCLUSIONS

US hospital stays for empyema in children not only continued to increase through 2009 but were also characterized by more intense procedural management. Outcomes results in this population-based study are consistent with practice guidelines and recommendations that recently endorsed chest tube drainage as an acceptable first treatment option for most children with empyema.

Pneumococcal empyema and complicated pneumonias: global trends in incidence, prevalence, and serotype epidemiology

This review evaluates the serotype epidemiology of complicated pneumococcal pneumonia (CPP) during the period 1990–2012. PubMed and EMBASE were searched using the terms “empyema”, “complicated pneumonia”, “pleural infection”, “necrotizing pneumonia”, “pleural effusion”, “parapneumonic effusion”, “pneumatocele”, or “lung abscess”; “pneumococcal” or “Streptococcus pneumoniae”; and “serotype” for studies on the epidemiology of complicated pneumonias published from January 1, 1990 to October 1, 2013. Studies with data on incidence and serotypes were included; reviews, case reports, and conference abstracts were excluded. Of 152 papers, 84 fitted the inclusion criteria. A few pneumococcal serotypes were predominant causes of CPP, particularly serotypes 1, 19A, 3, 14, and 7F. CPP was a more common manifestation of pneumococcal disease among older (>2 years old) than younger children. The data support increases in both reported incidence rates and proportions of CPP in children and adults during the period 1990–2012; specific increases varied by geographic region. The proportions of serotype 3 and, particularly in Asia, serotype 19A CPP have increased, whereas most studies show declines in serotype 14. Serotype 1 has been a predominant cause of CPP since 1990, while antibiotic resistance was infrequent among serotype 1 isolates. The reported incidence and proportions of CPP among pneumonia cases steadily increased from 1990 to 2012. Several factors might account for these increases, including enhanced disease detection due to a higher index of suspicion, more sophisticated diagnostic assays, and changes in the prevalence of serotypes with capacity to invade the pleural space that were not targeted by the 7-valent pneumococcal conjugate vaccine (PCV7).

Initial effects of the National PCV7 Childhood Immunization Program on adult invasive pneumococcal disease in Israel

Background

PCV7 was introduced as universal childhood vaccination in Israel in July 2009 and PCV13 in November 2010. Here we report data on adult invasive pneumococcal disease (IPD), two years post PCV7 implementation and before an expected effect of PCV13.

Methods

An ongoing nationwide active-surveillance (all 27 laboratories performing blood cultures in Israel), providing all blood & CSF S. pneumoniae isolates from persons >18 y was initiated in July 2009. Capture-recapture method assured reporting of >95% cases. All isolates were serotyped in one central laboratory. IPD outcome and medical history were recorded in 90%. Second year post PCV implementation is compared to the first year.

Results

During July 2009 to June 2011, 970 IPD cases were reported (annual incidence [/100,000] of 9.17 and 10.16 in the two consecutive years, respectively). Respective case fatality rates (CFRs) were 20% and 19.1%. Incidence of IPD and CFR increased with age and number of comorbidities. Incidence rate was significantly greater during the second winter, 7.79/100,000 vs. 6.14/100,000 in first winter, p = 0.004, with a non-significant decrease during summer months (3.02 to 2.48/100,000). The proportion of IPD cases due to PCV7-serotypes decreased from 27.5% to 13.1% (first to second year) (p<0.001). Yet, non-PCV13-strains increased from 32.7% to 40.2% (p = 0.017). The increase in non-PCV13-strains was highly significant in immunocompromised patients and to a lesser degree in non-immunocompromised at risk or in older patients (>64 y). Among younger/healthier patients serotype 5 was the major increasing serotype. Penicillin and ceftriaxone resistance decreased significantly in the second year.

Conclusions

While overall annual incidence of IPD did not change, the indirect effect of PCV7 vaccination was evident by the significant decrease in PCV7 serotypes across all age groups. Increase in non-VT13 strains was significant in immunocompromised patients. A longer follow-up is required to appreciate the full effect of infant vaccination on annual IPD.

Improving the Diagnosis, Management, and Outcomes of Children with Pneumonia: Where are the Gaps?

Pneumonia is the greatest contributor to childhood mortality and morbidity in resource-poor regions, while in high-income countries it is one of the most common reasons for clinic attendance and hospitalization in this age group. Furthermore, pneumonia in children increases the risk of developing chronic pulmonary disorders in later adult life. While substantial advances in managing childhood pneumonia have been made, many issues remain, some of which are highlighted in this perspective. Multiple studies are required as many factors that influence outcomes, such as etiology, patient characteristics, and prevention strategies can vary between and within countries and regions. Also, outside of vaccine studies, most randomized controlled trials (RCTs) on pneumonia have been based in resource-poor countries where the primary aim is usually prevention of mortality. Few RCTs have focused on medium to long-term outcomes or prevention. We propose different tiers of primary outcomes, where in resource-rich countries medium to long-term sequelae should also be included and not just the length of hospitalization and readmission rates.

Making valid causal inferences from observational data

The ability to make strong causal inferences, based on data derived from outside of the laboratory, is largely restricted to data arising from well-designed randomized control trials. Nonetheless, a number of methods have been developed to improve our ability to make valid causal inferences from data arising from observational studies. In this paper, I review concepts of causation as a background to counterfactual causal ideas; the latter ideas are central to much of current causal theory. Confounding greatly constrains causal inferences in all observational studies. Confounding is a biased measure of effect that results when one or more variables, that are both antecedent to the exposure and associated with the outcome, are differentially distributed between the exposed and non-exposed groups. Historically, the most common approach to control confounding has been multivariable modeling; however, the limitations of this approach are discussed. My suggestions for improving causal inferences include asking better questions (relates to counterfactual ideas and "thought" trials); improving study design through the use of forward projection; and using propensity scores to identify potential confounders and enhance exchangeability, prior to seeing the outcome data. If time-dependent confounders are present (as they are in many longitudinal studies), more-advanced methods such as marginal structural models need to be implemented. Tutorials and examples are cited where possible.

Conjugation of polysaccharide 6B from Streptococcus pneumoniae with pneumococcal surface protein A: PspA conformation and its effect on the immune response

Despite the substantial beneficial effects of incorporating the 7-valent pneumococcal conjugate vaccine (PCV7) into immunization programs, serotype replacement has been observed after its widespread use. As there are many serotypes currently documented, the use of a conjugate vaccine relying on protective pneumococcal proteins as active carriers is a promising alternative to expand PCV coverage. In this study, capsular polysaccharide serotype 6B (PS6B) and recombinant pneumococcal surface protein A (rPspA), a well-known protective antigen from Streptococcus pneumoniae, were covalently attached by two conjugation methods. The conjugation methodology developed by our laboratory, employing 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) as an activating agent through carboxamide formation, was compared with reductive amination, a classical methodology. DMT-MM-mediated conjugation was shown to be more efficient in coupling PS6B to rPspA clade 1 (rPspA1): 55.0% of PS6B was in the conjugate fraction, whereas 24% was observed in the conjugate fraction with reductive amination. The influence of the conjugation process on the rPspA1 structure was assessed by circular dichroism. According to our results, both conjugation processes reduced the alpha-helical content of rPspA; reduction was more pronounced when the reaction between the polysaccharide capsule and rPspA1 was promoted between the carboxyl groups than the amine groups (46% and 13%, respectively). Regarding the immune response, both conjugates induced functional anti-rPspA1 and anti-PS6B antibodies. These results suggest that the secondary structure of PspA1, as well as its reactive groups (amine or carboxyl) involved in the linkage to PS6B, may not play an important role in eliciting a protective immune response to the antigens.

DNA bacterial load in children with bacteremic pneumococcal community-acquired pneumonia

This study was conducted to evaluate the association between pneumococcal DNA load and parapneumonic pleural effusion (PPE) in children with community-acquired pneumonia. Bacterial load was quantified and related to the presence of PPE with or without empyema in 72 otherwise healthy children aged ≤5 years who were hospitalised because of radiographically confirmed CAP and showed a real-time polymerase chain reaction that was positive for Streptococcus pneumoniae. The proportion of children with a high bacterial load (i.e. ≥265 DNA copies/mL) was larger among the subjects with PPE than those without it. Multivariate analysis showed that a high bacterial load was significantly associated with PPE (OR 8.65; 95% CI 1.10-67.8 vs a bacterial load of <125 copies/mL). Children with infection due to pneumococcal serotype 19A were at highest risk of developing PPE (OR 7.44; 95% CI 1.10-50.4 vs all other typeable serotypes). The patients with CAP due to pneumococcal serotypes that are not included in the 13-valent conjugate vaccine (PCV13) were more frequently affected by PPE than those with infections associated with serotypes included in the vaccine, except for serotype 19A. Bacterial loads of ≥265 DNA copies/mL are significantly associated with PPE, and serotype 19A is significantly associated with a high bacterial load and the development of PPE. The mean bacterial load of the patients with empyema was higher than that of patients with simple PPE. Although further studies are required, it seems that serotypes not included in PCV13 can play a major role in causing a higher bacterial load and PPE.

Pharmacotherapy for pneumococcal infections: an update

INTRODUCTION

The management of pneumococcal diseases still places a significant burden on medical and economic resources. The subjects at greatest risk of pneumococcal infections are children.

AREAS COVERED

The aim of this review is to analyse the best current therapeutic approach to pneumococcal resistance, taking into account the level of susceptibility of Streptococcus pneumoniae, and the pharmacokinetics and pharmacodynamics of different antibiotics in the various pneumococcal diseases.

EXPERT OPINION

Antibiotic treatment of a number of pneumococcal diseases remains difficult or impossible due to the presence of strains resistant to commonly used antibiotics. In children the problem is significantly more important than in adults due to the reduced number of licenced drugs for subjects in the first years of life. The new conjugate pneumococcal vaccines containing 10 (PCV10) and 13 serotypes (PCV13), which include most of the recently emerging strains, might reduce the incidence of pneumococcal infections and the circulation of resistant pathogens. However, it is likely that optimal results will only be reached after the development of effective vaccines based on conserved proteins that are capable of preventing all pneumococcal infections, regardless of the serotype of the causative organism.

Comparative analysis of the humoral immune response to Moraxella catarrhalis and Streptococcus pneumoniae surface antigens in children suffering from recurrent acute otitis media and chronic otitis media with effusion

A prospective clinical cohort study was established to investigate the humoral immune response in middle ear fluids (MEF) and serum against bacterial surface proteins in children suffering from recurrent acute otitis media (rAOM) and chronic otitis media with effusion (COME), using Luminex xMAP technology. The association between the humoral immune response and the presence of Moraxella catarrhalis and Streptococcus pneumoniae in the nasopharynx and middle ear was also studied. The levels of antigen-specific IgG, IgA, and IgM showed extensive interindividual variation. No significant differences in anti-M. catarrhalis and anti-S. pneumoniae serum and MEF median fluorescence intensity (MFI) values (anti-M. catarrhalis and antipneumococcal IgG levels) were observed between the rAOM or COME groups for all antigens tested. No significant differences were observed for M. catarrhalis and S. pneumoniae colonization and serum IgG levels against the Moraxella and pneumococcal antigens. Similar to the antibody response in serum, no significant differences in IgG, IgA, and IgM levels in MEF were observed for all M. catarrhalis and S. pneumoniae antigens between OM M. catarrhalis- or S. pneumoniae-positive and OM M. catarrhalis- or S. pneumonia-negative children suffering from either rAOM or COME. Finally, results indicated a strong correlation between antigen-specific serum and MEF IgG levels. We observed no significant in vivo expressed anti-M. catarrhalis or anti-S. pneumoniae humoral immune responses using a range of putative vaccine candidate proteins. Other factors, such as Eustachian tube dysfunction, viral load, and genetic and environmental factors, may play a more important role in the pathogenesis of OM and in particular in the development of rAOM or COME.

The changing epidemiology of invasive pneumococcal disease at a tertiary children's hospital through the 7-valent pneumococcal conjugate vaccine era: a case for continuous surveillance

BACKGROUND

In 2000, a 7-valent pneumococcal conjugate vaccine (PCV7) was licensed for use among US children. Many sites have since reported changes in invasive pneumococcal disease (IPD). We recognized an opportunity to describe the changes in epidemiology, clinical syndromes, and serotype distribution during a 14-year period including 4 years before vaccine introduction and spanning the entire PCV7 era.

METHODS

Cases were defined as children <18 years of age who were cared for at Primary Children's Medical Center for culture-confirmed IPD. We defined the prevaccine period as the time frame spanning from 1997 to 2000 and the postvaccine period from 2001 to 2010. Demographics, clinical data, and outcomes were collected through electronic query and chart review. Streptococcus pneumoniae serotyping was performed using the capsular swelling method.

RESULTS

The median age of children with IPD increased from 19 months during the prevaccine period to 27 months during postvaccine period (P = 0.02), with a larger proportion of IPD among children older than 5 years. The proportion of IPD associated with pneumonia increased substantially from 29% to 50% (P < 0.001). This increase was primarily attributable to an increase in complicated pneumonia (17% to 33%, P < 0.001). Nonvaccine serotypes 7F, 19A, 22F, and 3 emerged as the dominant serotypes in the postvaccine period. In children with IPD who were younger than 5 years, for whom vaccine is recommended, 67% of the cases were caused by serotypes in 13-valent PCV during 2005 to 2010.

CONCLUSIONS

After PCV7 was introduced, significant changes in IPD were noted. One-third of IPD occurred in children older than 5 years, who were outside the age-group for which PCV is recommended. Continued surveillance is warranted to identify further evolution of the epidemiology, clinical syndromes, and serotype distribution of S. pneumoniae after 13-valent PCV licensure.

Pneumococcal disease manifestation in children before and after vaccination: what's new?

Pneumococcal infections remain a relevant cause of morbidity and mortality in children, especially in countries where vaccination has not been introduced. In contrast to the common belief by many pediatricians, the most important pneumococcal infections are of the respiratory tract and not invasive diseases. The recent pandemic of the H1N1 virus prompted studies to better understand the interaction between the influenza virus, Streptococcus pneumoniae, and pneumonia outcomes. Radiological findings of bacteremic pneumonia have been well investigated and besides the typical alveolar consolidation, a broad spectrum of atypical patterns has been reported. Molecular techniques, such as real-time polymerase chain reaction (PCR), can improve the detection of S. pneumoniae in sterile fluids, mainly in regions where previous antibiotic therapy is a common practice. In the post vaccination era, new manifestations of pneumococcal invasive disease, such as hemolytic uremic syndrome, have increased in association with parapneumonic empyema. Moreover, serotypes not included in PCV7, particularly serotypes 1, 3, 5, 7F, and 19A, have been among the most common isolates in pneumococcal disease. In Latin America, pneumococcal primary peritonitis has been described as an important clinical syndrome in a growing proportion of patients, mainly in girls. The development of newer and more specific diagnostic markers to distinguish bacterial and viral pneumonia are urgently sought, and will be especially pertinent after the introduction of pneumococcal conjugate vaccines with expanded serotypes. Such markers would minimize inappropriate diagnosis of false positive cases and treatment with antibacterial agents, while increasing positive predictive values for diagnosis of bacterial pneumonia. The extension of serotype coverage with the new conjugate vaccines is promising for pneumococcal infections and coverage against antibiotic-resistant strains.

Serotype replacement in disease after pneumococcal vaccination

Vaccination with heptavalent pneumococcal conjugate vaccine (PCV7) has significantly reduced the burden of pneumococcal disease and has had an important public health benefit. Because this vaccine targets only seven of the more than 92 pneumococcal serotypes, concerns have been raised that non-vaccine serotypes (NVTs) could increase in prevalence and reduce the benefits of vaccination. Indeed, among asymptomatic carriers, the prevalence of NVTs has increased substantially, and consequently, there has been little or no net change in the bacterial carriage prevalence. In many populations, pneumococcal disease caused by NVT has increased, but in most cases this increase has been less than the increase in NVT carriage. We review the evidence for serotype replacement in carriage and disease, and address the surveillance biases that might affect these findings. We then discuss possible reasons for the discrepancy between near-complete replacement in carriage and partial replacement for disease, including differences in invasiveness between vaccine serotypes. We contend that the magnitude of serotype replacement in disease can be attributed, in part, to a combination of lower invasiveness of the replacing serotypes, biases in the pre-vaccine carriage data (unmasking), and biases in the disease surveillance systems that could underestimate the true amount of replacement. We conclude by discussing the future potential for serotype replacement in disease and the need for continuing surveillance.

Diagnosis of pneumococcal empyema using immunochromatographic test on pleural fluid and serotype distribution in Korean children

To evaluate the diagnostic value of immunochromatographic test (ICT) on pleural fluid in diagnosing pneumococcal empyema in children and to determine pneumococcal serotypes, 62 exudative parapneumonic effusions from Korean children were tested with culture, ICT for S. pneumoniae, pneumococcal autolysin polymerase chain reaction (PCR), and subsequent sequencing. Of the 62 patients, culture was positive in 3 patients only (4.8%). Pneumococci were identified in 13 samples (21.0%) by sequencing-confirmed PCR and ICT, respectively. When pneumococcal empyema was defined by either positive culture or sequence confirmation, the sensitivity of ICT was 76.9% (10/13) and the specificity of ICT was 93.9%. Eight of 10 patients with positive ICT and culture-negative results had a history of prior antibiotics use, whereas none of the culture-proven cases had. Serotypes of PCR-positive samples were determined by multiplex PCR assays. Multiplex PCR detected serotypes 19A (6), 1 (1), 14 (1), 34 (1), and untypable (4). ICT on pleural fluid is a relatively sensitive and highly specific method for diagnosis of pneumococcal empyema, especially in children given prior antibiotics.

Pulmonary complications of pneumococcal community-acquired pneumonia: incidence, predictors, and outcomes

The aim of this study was to evaluate the clinical characteristics, predictors and outcomes of pneumococcal pneumonia developing pulmonary complications and the distribution of pneumococcal serotypes. It was a prospective study including all adult patients admitted to the Hospital Clinic of Barcelona, Spain (2001-2009) with the diagnosis of pneumococcal pneumonia. Microbiological investigation was systematically performed, including antimicrobial susceptibility and serotype distribution (only invasive strains isolated during 2006-2009). Complicated pneumonia was defined as the presence of one or more pulmonary complications: pleural effusion, empyema, or multilobar infiltrates. We included 626 patients, and 235 (38%) had the following pulmonary complications: pleural effusion, 122 (52%); empyema, 18 (8%); and multilobar infiltration, 151 (64%). Forty-six (20%) patients had more than one complication. Patients with pulmonary complications showed a higher rate of intensive-care unit admission (34% vs. 13%, p <0.001), a higher rate of shock (16% vs. 7%, p <0.001), a longer length of stay (9 days vs. 6 days, p <0.001), and a lower rate of penicillin resistance (14% vs. 25%, p 0.013), but similar mortality (9% vs. 8%). No significant differences were observed in the serotype distribution between complicated and uncomplicated pneumonia. Chronic obstructive pulmonary disease (COPD) (OR 0.38, 95% CI 0.23-0.63; p <0.001) was a protective factor against pulmonary complications, whereas chronic liver disease (OR 3.60, 95% CI 1.71-7.60; p 0.001), admission C-reactive protein level ≥18 mg/dL (OR 2.77, 95% CI 1.91-4.00; p <0.001) and admission creatinine level >1.5 mg/dL (OR 2.01, 95% CI 1.31-3.08; p 0.001) were risk factors for pulmonary complications. Complicated pneumonia was characterized by a more severe clinical presentation, but was not associated with increased mortality. Resistance to antibiotics was lower in complicated cases. No significant differences were observed in the serotype distribution between complicated and uncomplicated pneumonia. In the multivariate analysis, COPD was a protective factor against pulmonary complications.

A multiplex polymerase chain reaction method for rapid pneumococcal serotype determination in childhood empyema

Nonvaccine serotypes are increasingly responsible for pneumococcal empyema. We developed a one-step polymerase chain reaction for identifying all serotypes covered by the 13-valent conjugate vaccine. Over 1 year, we identified serotypes 19A (n = 6), 1 (n = 2), 3 (n = 1) and 7F/A (n = 2), both in culture-positive and culture-negative pleural fluid from 11 children with empyema.

Economic evaluation of pneumococcal conjugate vaccination in The Gambia

BACKGROUND

Gambia is the second GAVI support-eligible country to introduce the 7-valent pneumococcal conjugate vaccine (PCV7), but a country-specific cost-effectiveness analysis of the vaccine is not available. Our objective was to assess the potential impact of PCVs of different valences in The Gambia.

METHODS

We synthesized the best available epidemiological and cost data using a state-transition model to simulate the natural histories of various pneumococcal diseases. For the base-case, we estimated incremental cost (in 2005 US dollars) per disability-adjusted life year (DALY) averted under routine vaccination using PCV9 compared to no vaccination. We extended the base-case results for PCV9 to estimate the cost-effectiveness of PCV7, PCV10, and PCV13, each compared to no vaccination. To explore parameter uncertainty, we performed both deterministic and probabilistic sensitivity analyses. We also explored the impact of vaccine efficacy waning, herd immunity, and serotype replacement, as a part of the uncertainty analyses, by assuming alternative scenarios and extrapolating empirical results from different settings.

RESULTS

Assuming 90% coverage, a program using a 9-valent PCV (PCV9) would prevent approximately 630 hospitalizations, 40 deaths, and 1000 DALYs, over the first 5 years of life of a birth cohort. Under base-case assumptions ($3.5 per vaccine), compared to no intervention, a PCV9 vaccination program would cost $670 per DALY averted in The Gambia. The corresponding values for PCV7, PCV10, and PCV13 were $910, $670, and $570 per DALY averted, respectively. Sensitivity analyses that explored the implications of the uncertain key parameters showed that model outcomes were most sensitive to vaccine price per dose, discount rate, case-fatality rate of primary endpoint pneumonia, and vaccine efficacy against primary endpoint pneumonia.

CONCLUSIONS

Based on the information available now, infant PCV vaccination would be expected to reduce pneumococcal diseases caused by S. pneumoniae in The Gambia. Assuming a cost-effectiveness threshold of three times GDP per capita, all PCVs examined would be cost-effective at the tentative Advance Market Commitment (AMC) price of $3.5 per dose. Because the cost-effectiveness of a PCV program could be affected by potential serotype replacement or herd immunity effects that may not be known until after a large scale introduction, type-specific surveillance and iterative evaluation will be critical.