Failures of 13-Valent Conjugated Pneumococcal Vaccine in Age-Appropriately Vaccinated Children 2-59 Months of Age, Spain

Bacterial cholesterol-dependent cytolysins and their interaction with the human immune response

PURPOSE OF REVIEW

Many cholesterol-dependent cytolysin (CDC)-producing pathogens pose a significant threat to human health. Herein, we review the pore-dependent and -independent properties CDCs possess to assist pathogens in evading the host immune response.

RECENT FINDINGS

Within the last 5 years, exciting new research suggests CDCs can act to inhibit important immune functions, disrupt critical cell signaling pathways, and have tissue-specific effects. Additionally, recent studies have identified a key region of CDCs that generates robust immunity, providing resources for the development of CDC-based vaccines.

SUMMARY

This review provides new information on how CDCs alter host immune responses to aid bacteria in pathogenesis. These studies can assist in the design of more efficient vaccines and therapeutics against CDCs that will enhance the immune response to CDC-producing pathogens while mitigating the dampening effects CDCs have on the host immune response.

Pneumococcal Vaccine Breakthrough and Failure in Infants and Children: A Narrative Review

Globally, Streptococcus pneumoniae is a leading cause of vaccine-preventable morbidity and mortality in infants and children. In recent decades, large-scale pediatric immunization programs have substantially reduced the incidence of invasive pneumococcal disease. Despite this, residual vaccine-type pneumococcal disease remains in the form of vaccine breakthrough and vaccine failure. This targeted literature review aims to discuss aspects of vaccine breakthrough and failure in infants and children, including disease epidemiology, clinical presentation, risk factors, vaccination schedules, vaccine serotypes, correlates of protection, comorbidities, disease surveillance, and potential implications for future vaccine development.

Multi epitope vaccine candidate design against Streptococcus pneumonia

Streptococcus pneumonia, the causative agent of sepsis, meningitis and pneumonia, is held responsible for causing invasive diseases predominantly in children along with adults from both developing and developed countries. The available vaccines coverage in the context of different serotypes is limited and emergence of non-vaccine serotypes could further emerge as a threat in future. Advanced immunoinformatics tools have been used for developing a multi epitope subunit vaccine. In the current study we have subjected these four surface antigenic proteins Ply, PsaA, PspA and PspK to construct vaccine designs. We have predicted different B-cell and T-cell epitopes by using NetCTL 1.2, IEDB (Immune Epitope Databases) and ABCpred. An adjuvant (griselimycin) has been added to the vaccine construct sequence in order to improve its immunogenicity. The vaccine construct has been evaluated for its antigenicity, allergenicity, toxicity and different physio-chemical properties. The bioinformatic tools have been used for prediction, refinement and validation of the 3 D structure. Further, the vaccine structure has been docked with a toll-like receptor (TLR-4) by ClusPro 2.0. In conclusion, the proposed multi-epitope vaccine designs could potentially activate both humoral and cellular immune responses and has a potential to be a vaccine candidate against S.pneumoniae, and requires experimental validation for ensuring immunogenicity and safety profile.Communicated by Ramaswamy H. Sarma.

Continued Vaccine Breakthrough Cases of Serotype 3 Complicated Pneumonia in Vaccinated Children, Portugal (2016-2019)

We previously reported that despite the use of pneumococcal conjugate vaccines (PCVs), vaccine serotypes remained important causes of pneumonia with pleural effusion and empyema (pediatric complicated pneumococcal pneumonia [PCPP]). We cultured and performed PCR on 174 pleural fluid samples recovered from pediatric patients in Portugal from 2016 to 2019 to identify and serotype Streptococcus pneumoniae. Most PCPP cases (n = 87/98) were identified by PCR only. Serotypes 3 (67%), 14, and 8 (5% each) were the most frequent. Vaccine breakthrough cases were seen among age-appropriately, 13-valent, PCV vaccinated children (median: 3 years, range: 17 months to 7 years), mostly with serotype 3 (n = 27) but also with serotypes 14 and 19A (n = 2 each). One breakthrough was seen with serotype 14 in an age-appropriately, 10-valent, PCV-vaccinated child and another with serotype 3 in a child to whom the 23-valent polysaccharide vaccine was administered. While the relative risk of serotype 1 PCPP decreased almost 10-fold from the period of 2010 to 2015 to the period of 2016 to 2019 (relative risk [RR] = 0.106), that of serotype 3 PCPP almost doubled (RR = 1.835). Our data highlight the importance of molecular diagnostics in identifying PCPP and document the continued importance of serotype 3 PCPP, even when PCV13 use with almost universal coverage could be expected to reduce exposure to this serotype. IMPORTANCE The use of conjugate vaccines against Streptococcus pneumoniae in children has led to substantial reductions in pneumococcal invasive disease. However, the reductions seen in each of the 13 serotypes currently included in the highest-valency vaccine approved for use in children (PCV13), were not the same. It is becoming clear that most vaccine breakthroughs worldwide involve serotype 3 and are frequently associated with complicated pneumonia cases, often with empyema or pleural effusion. Here, we show that despite almost universal PCV13 use, which would be expected to reduce vaccine serotype circulation and further reinforce vaccine direct protection, pneumococci and serotype 3 remain the major causes of pediatric complicated pneumonia. Molecular methods are essential to identify and serotype pneumococci in these cases, which frequently reflect vaccine breakthroughs. A broader use of molecular diagnostics will be essential to determine the role of this important serotype in the context of PCV13 use in different geographic regions.

Pneumococcal meningitis in Greece: A retrospective serotype surveillance study in the post-PCV13 era (2010-2020)

BACKGROUND

As Greece is a country which has introduced the 13-valent pneumococcal conjugate vaccine (PCV13) both in the infant and in the adult immunization programs, the aim of the study was to investigate age-specific and serotype-specific trends of pneumococcal meningitis over an 11-year period (2010-2020).

MATERIALS AND METHODS

Data are reported from pneumococcal meningitis cases [notified to the National Public Health Organization (NPHO)], with clinical samples and bacterial isolates sent for pneumococcal identification and serotyping at the National Meningitis Reference Laboratory (NMRL). Pneumococcal identification was performed directly on clinical samples or bacterial isolates by multiplex PCR (mPCR) assay, while serotyping was carried out by application of the Capsular Sequence Typing (CST) method with the combination of single tube PCR assays.

RESULTS

A total of 427 pneumococcal meningitis cases were notified to the NPHO between 2010 and 2020. Among those, 405 (94.8%) were microbiologically confirmed, while samples from 273 patients were sent to the NMRL for identification and/or further typing. The annual notification rate peaked at 0.47/100,000 in 2016 and since then has been decreasing. The incidence was highest in infants and in older adults. Pneumococcal serotypes were identified in 260/273 (95.2%) cases, where clinical samples were sent to the NMRL. The most prevalent serotypes (≥5%) were 3, 19A, 23B, 15B/C, 11A/D, 23A, 22F. During the study period there has been a decrease of PCV13 serotypes combined with an increase of non-PCV13 serotypes (p = 0.0045).

CONCLUSIONS

This is the first study to report serotypes for pneumococcal meningitis across all ages in the post-PCV13 era in Greece. There is a need to enhance surveillance, by close monitoring of the emerging serotypes and the impact of vaccination programs. Higher-valency PCVs may help to improve the coverage of pneumococcal disease.

A systematic review of invasive pneumococcal disease vaccine failures and breakthrough with higher-valency pneumococcal conjugate vaccines in children

INTRODUCTION

: The pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV or PCV10) and 13-valent pneumococcal conjugate vaccine (PCV13) protect against vaccine-serotype invasive pneumococcal disease (VT IPD). However, VT IPD can still occur in fully or partially vaccinated children (vaccine failure or breakthrough). We performed a systematic review of vaccine failures and breakthrough IPD with PCV10 and PCV13 in ≤5-year-olds.

AREAS COVERED

: We searched Scopus/Medline/EMBASE to retrieve articles/abstracts published between 1/2008-7/2019. We excluded reports from studies only including data from adults or children ≥6 years, exclusively assessing PCV7-vaccinated children or children with underlying comorbidities. Twenty-six reports (20 PCV13, 1 PCV10, 5 both), covering studies with various designs in six continents, using different schedules, were included. Collectively, these studies reported 469 VT IPD cases classified as vaccine failures and 403 as breakthrough. Vaccine failure and breakthrough rates were low: 8.4% and 9.3%, respectively, of all IPD in vaccinated children, consistent with the vaccines' high effectiveness. The main serotypes associated with vaccine failure or breakthrough were 19A, 3 and 19F in PCV13 studies and 14, 6B and vaccine-related 19A and 6A in PCV10 studies.

EXPERT OPINION

: As we move to vaccines with more serotypes, it is not only important to consider which serotypes are added, but also to monitor and address incomplete protection against specific serotypes.

Pediatric Invasive Pneumococcal Disease Three Years after PCV13 Introduction in the National Immunization Plan-The Continued Importance of Serotype 3

The introduction of pneumococcal conjugate vaccines PCV7 and PCV13 led to decreases in incidence of pediatric invasive pneumococcal disease (pIPD) and changes in serotype distribution. We evaluated the consequences of higher vaccine uptake after the introduction of PCV13 in the National Immunization Plan (NIP) in 2015. Besides culture and conventional serotyping, the use of molecular methods to detect and serotype pneumococci in both pleural and cerebrospinal fluid samples contributed to 30% of all pIPD (n = 232) in 2015–2018. The most frequently detected serotypes were: 3 (n = 59, 26%), 10A (n = 17, 8%), 8 (n = 16, 7%) and 19A (n = 10, 4%). PCV13 serotypes still accounted for 46% of pIPD cases. Serotypes not included in any currently available conjugate vaccine (NVT) are becoming important causes of pIPD, with the increases in serotypes 8 and 33F being of particular concern given the importance of serotype 8 in adult IPD and the antimicrobial resistance of serotype 33F isolates. This study highlights the importance of using molecular methods in pIPD surveillance since these allowed a better case ascertainment and the identification of serotype 3 as the leading cause of pIPD. Even in a situation of vaccine uptake >95% for 3 years, PCV13 serotypes remain important causes of pIPD.

Exploring the evidence behind the comparable impact of the pneumococcal conjugate vaccines PHiD-CV and PCV13 on overall pneumococcal disease

The worldwide implementation of pneumococcal conjugate vaccines (PCVs) in children has reduced the overall pneumococcal disease burden. Two PCVs are widely available for infant vaccination: the pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) and the 13-valent PCV (PCV13). While these PCVs differ in serotype composition (PCV13 includes polysaccharides of serotypes 3, 6A and 19A; PHiD-CV does not), their impact on the overall pneumococcal disease burden in children is comparable. This commentary summarizes the evidence of comparability between PHiD-CV and PCV13 and explores why differences in serotype composition may not necessarily translate into a differential clinical impact. Both vaccines confer similarly high protection against disease caused by vaccine serotypes and lead to a partial replacement by non-vaccine serotypes. PHiD-CV does not protect against serotype 3 disease (not included in the vaccine) and PCV13’s effect on this serotype has been inconsistent. PHiD-CV provides some cross-protection against disease caused by vaccine-related serotype 19A but neither vaccine has fully controlled 19A disease. While protection against 19A is higher for PCV13 than PHiD-CV, replacement by non-PCV13 serotypes in settings with a PCV13 program appears to compensate for this difference. This results in a similar residual overall disease burden with both vaccines.

What is the context?

The pneumococcus bacterium can cause infections of the meninges, blood, lung, middle ear and sinuses.

Two vaccins, Synflorix (GSK) and Prevnar 13 (Pfizer Inc.), are widely used to protect young children against these infections.

The vaccines’ compositions differ: Synflorix includes antigens from 10 pneumococcus strains (or “serotypes”) and Prevnar 13 from 13 serotypes.

However, both have a similar effect on the total pneumococcal disease burden in children.

What does this commentary highlight?

This commentary summarizes the evidence beihnd the two vaccines’ comparable impact on pneumococcal disase.

It also looks at why the vaccines have a similar effect on the total pneumococcal disease burden despite their different compositions.

What is the impact on current thinking?

Given that Synflorix and Prevnar 13 have a comparable impact on pneumococcal disease, a country’s choice between the two vaccines will depend on vaccine supply, cost, logistical factors (e.g., transport, storage, training requirements of health workers) and the local pneumococcal epidemiology.

Impact of the 13-Valent Conjugated Pneumococcal Vaccine on the Direct Costs of Invasive Pneumococcal Disease Requiring Hospital Admission in Children Aged < 5 Years: A Prospective Study

The lack of invasive pneumococcal disease (IPD) cost studies may underestimate the eect ofpneumococcal polysaccharide conjugated vaccines (PCV). The objective of this study was to estimatethe direct costs of hospitalized IPD cases. A prospective study was made in children aged <5 yearsdiagnosed with IPD in two high-tech hospitals in Catalonia (Spain) between 2007-2009 (PCV7 period)and 2012-2015 (PCV13 period). Costs were calculated according to 2014 Catalan Health Service ratesusing diagnostic-related groups. In total, 319 and 154 cases were collected, respectively. Pneumoniahad the highest cost (65.7% and 62.0%, respectively), followed by meningitis (25.8% and 26.1%,respectively). During 2007-2015, the costs associated with PCV7 serotypes (Pearson coecient (Pc) =?0.79; p = 0.036) and additional PCV13 serotypes (Pc = ?0.75; p = 0.05) decreased, but those of otherserotypes did not (Pc = 0.23 p = 0.62). The total mean cost of IPD increased in the PCV13 period by31.4% (¿3016.1 vs. ¿3963.9), mainly due to ICU stay (77.4%; ¿1051.4 vs. ¿1865.6). During the PCV13period, direct IPD costs decreased due to a reduction in the number of cases, but cases were more severe and had a higher mean cost. During 2015, IPD costs increased due to an increase in the costsassociated with non-PCV13 serotypes and serotype 3 and this requires further investigation.

Influence of pneumococcal vaccination on the hospitalization of healthy pediatric patients due to typical Community-Acquired Pneumonia

INTRODUCTION

Community-Acquired Pneumonia (CAP) is one of the most frequent causes of hospital admission in children. Our objective is to measure the impact of the introduction of pneumococcal conjugate vaccines on the hospitalization of previously healthy children due to CAP.

METHOD

From 2011 to 2016, a partially retrospective, prospective, and descriptive study was carried out on healthy pediatric patients (3 months-14 years old) with CAP, who required hospital admission. Clinical, epidemiological, and demographic characteristics were collected, and vaccination status was obtained from medical records.

RESULTS

A total of 292 cases were included, with a mean age of 33.4 months, 54% males. There was a progressive and significant 42% decrease in the number of admissions each year, without significant changes in the annual percentage of parapneumonic pleural effusion (PPE). Fifty-six percent of patients were immunized with a pneumococcal conjugate vaccine (PCV). The percentage of children who were not vaccinated decreased by 14%, and the coverage with PCV-13 increased by 46%. This revealed a significant increase of PPE in vaccinated patients with PCV-7 (63%) compared with unvaccinated (45%) and with PCV-13 (57%), without association with the presence of severe PPE. Moreover, no significant differences in severity or hospital stay were observed in unvaccinated patients, compared to those who were vaccinated. In >2-year-olds, we observed a significant increase in PPE (59%) compared to 45% in younger children.

CONCLUSIONS

The increase in vaccination coverage with PCV-13 resulted in a decrease in hospitalizations due to CAP and PPE. Vaccination with PCV-7 is associated in our sample with an increase in PPE but not with severe PPE nor an increase in the hospital stay. There was an epidemiological shift of severe forms of pneumonia and empyema at later ages (>2 years).