Vaccination of Icelandic Children with the 10-Valent Pneumococcal Vaccine Leads to a Significant Herd Effect among Adults in Iceland

Effects of PCV10 and PCV13 on pneumococcal serotype 6C disease, carriage, and antimicrobial resistance

BACKGROUND

The cross-protection of pneumococcal conjugate vaccines (PCV) against serotype 6C is not clearly documented, although 6C represents a substantial burden of pneumococcal disease in recent years. A systematic review by the World Health Organization that covered studies through 2016 concluded that available data were insufficient to determine if either PCV10 (which contains serotype 6B but not 6A) or PCV13 (containing serotype 6A and 6B) conferred protection against 6C.

METHODS

We performed a systematic review of randomized controlled trials and observational studies published between January 2010 - August 2022 (Medline/Embase), covering the direct, indirect, and overall effect of PCV10 and PCV13 against 6C invasive pneumococcal disease (IPD), non-IPD, nasopharyngeal carriage (NPC), and antimicrobial resistance (AMR).

RESULTS

Of 2548 publications identified, 112 were included. Direct vaccine effectiveness against 6C IPD in children ranged between 70 and 85 % for ≥ 1 dose PCV13 (n = 3 studies), was 94 % in fully PCV13 vaccinated children (n = 2), and -14 % for ≥ 1 dose of PCV10 (n = 1). Compared to PCV7, PCV13 efficacy against 6C NPC in children was 66 % (n = 1). Serotype 6C IPD rates or NPC prevalence declined post-PCV13 in most studies in children (n = 5/6) and almost half of studies in adults (n = 5/11), while it increased post-PCV10 for IPD and non-IPD in all studies (n = 6/6). Changes in AMR prevalence were inconsistent.

CONCLUSIONS

In contrast to PCV10, PCV13 vaccination consistently protected against 6C IPD and NPC in children, and provided some level of indirect protection to adults, supporting that serotype 6A but not 6B provides cross-protection to 6C. Vaccine policy makers and regulators should consider the effects of serotype 6A-containing PCVs against serotype 6C disease in their decisions.

Indirect impact of PCV10 children vaccination on the serotype distribution and antimicrobial resistance of Streptococcus pneumoniae causing invasive disease in adults over 50 in Colombia, 2005-2019: Observational analysis

INTRODUCTION

The introduction of pneumococcal conjugate vaccine (PCV) into childhood vaccination programmes has reduced the prevalence of vaccine serotypes (VTs) that cause invasive pneumococcal disease (IPD) in children. In the elderly population, an impact has also been seen through indirect protection (herd effect). The aim of this study was to estimate the changes in serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae isolates recovered from adult IPD and to evaluate the indirect effect of immunization with PCV10 based on laboratory records by analyzing the period from 2005 to 2019 for six years before and eight years after the universal PCV10 administration to Colombian children.

METHODS

A total of 2204 S. pneumoniae isolates from adults (≥50 years) with IPD were analyzed. The analysis examined the percentage changes in proportions (prevalence) and percentage variations in population rates (annual reported rates - ARR) of VTs between the pre-PCV10 (2005-2009) and post-PCV10 (2015-2019) periods.

RESULTS

The findings were (1) evidence of a significant percentage decrease of pneumococcal VT10 causing IPD in adults (50% pre-PCV10 and 16% post-PCV10); (2) significant increase of serotype 19A (from 1.6% to 14.8%) and less important increase of serotype 3 (from 10.5% to 14.5%) and non-vaccine serotypes (NVT) (from 21.4% to 38.4%) non-significant; and (3) meningitis and non-meningitis multidrug resistant isolates associated with serotype 19A. An improvement in the surveillance system is associated with the immunization of children, as noted by the increased ARRs across the analysis period.

CONCLUSIONS

Our results show the indirect impact of PCV10 vaccination in children on the VT10 distribution and antimicrobial resistance of S. pneumoniae causing IPD in Colombian adults over 50 when comparing the pre-PCV10 (2005-2009) and post-PCV10 (2015-2019) periods.

Nasopharyngeal competition dynamics are likely to be altered following vaccine introduction: bacteriocin prevalence and diversity among Icelandic and Kenyan pneumococci

Bacteriocins are antimicrobial peptides produced by bacteria to inhibit other bacteria in the surrounding environment. Streptococcus pneumoniae is a leading cause of disease worldwide and colonises the healthy human nasopharynx, where it competes for space and nutrients. Pneumococcal conjugate vaccines have reduced the incidence of disease, but they also restructure the bacterial population, and this restructuring likely alters the nasopharyngeal competition dynamics. Here, the distribution of bacteriocins was examined in over 5000 carriage and disease-causing pneumococci from Iceland and Kenya, recovered before and after the introduction of pneumococcal vaccination. Overall, up to eleven different bacteriocin gene clusters were identified per pneumococcus. Significant differences in the prevalence of bacteriocins were observed before and after vaccine introduction, and among carriage and disease-causing pneumococci, which were largely explained by the bacterial population structure. Genetically similar pneumococci generally harboured the same bacteriocins although sometimes different repertoires of bacteriocins were observed, which suggested that horizontal transfer of bacteriocin clusters had occurred. These findings demonstrated that vaccine-mediated changes in the pneumococcal population altered the prevalence and distribution of bacteriocins. The consequences of this for pneumococcal colonisation and disease remain to be determined.

Pneumococcal Serotype Evolution and Burden in European Adults in the Last Decade: A Systematic Review

Pneumococcal disease is a major cause of morbidity/mortality worldwide, and vaccination is an important measure in its prevention. Despite European children being vaccinated with pneumococcal conjugate vaccines (PCVs), pneumococcal infections are still a major cause of morbidity/mortality in adults with risk conditions and their vaccination might be an important prevention strategy. New PCVs have been approved, but information is lacking on their potential impact in European adults. In our review, we searched PubMed, MEDLINE, and Embase for studies on the additional PCV20 serotypes (concerning incidence, prevalence, disease severity, lethality, and antimicrobial resistance) in European adults, between January 2010 and April 2022, having included 118 articles and data from 33 countries. We found that these serotypes have become more prevalent in both invasive and non-invasive pneumococcal disease (IPD and NIPD), representing a significant proportion of cases (serotypes 8, 12F, 22F) and more serious disease and/or lethality (10A, 11A, 15B, 22F), showing antimicrobial resistance (11A, 15B, 33F), and/or affecting more vulnerable individuals such as the elderly, immunocompromised patients, and those with comorbidities (8, 10A, 11A, 15B, 22F). The relevance of pneumococcal adult carriers (11A, 15B, 22F, and 8) was also identified. Altogether, our data showed an increase in the additional PCV20 serotypes' prevalence, accounting for a proportion of approximately 60% of all pneumococcal isolates in IPD in European adults since 2018/2019. Data suggest that adults, as older and/or more vulnerable patients, would benefit from vaccination with higher-coverage PCVs, and that PCV20 may address an unmet medical need.

The impact of the introduction of ten- or thirteen-valent pneumococcal conjugate vaccines on antimicrobial-resistant pneumococcal disease and carriage: A systematic literature review

Background

A systematic review in 2019 found reductions in antimicrobial resistance (AMR) of pneumococcal vaccine serotypes following pneumococcal conjugate vaccine (PCV) introduction. However, few low- or middle-income countries were included as not many had introduced higher valent PCVs (PCV10 or PCV13). The aim of our review is to describe AMR rates in these samples following the introduction of PCV10 or PCV13.

Methods

We conducted a systematic literature review of published papers that compared AMR for invasive pneumococcal disease (IPD), otitis media (OM) and nasopharyngeal carriage (NPC) samples following introduction of PCV10 or PCV13 to the pre-PCV period. Included studies published from July 2017 to August 2020 had a post-licensure observational study design and reported on our defined outcomes: IPD, OM, NPC and other (sputum or mixed invasive and non-invasive pneumococcal) isolates from people of all ages. Rates of AMR in the pre- and post-period were extracted.

Results

Data were extracted from 31 studies. Among IPD isolates, penicillin AMR rates following PCV10 or PCV13 introduction declined in 32% (n = 9/29) of included studies, increased in 34% (n = 10/29) and showed no change in 34% (n = 10/29). Cephalosporins AMR declined in 32% (n = 6/19) of studies, increased in 21% (n = 4/19) and showed no change in 47% (n = 9/19). Macrolides AMR declined in 33% (n = 4/12) of studies, increased in 50% (n = 6/12), and showed no change in 17% (n = 2/12). AMR to other antibiotics (including multidrug resistance) declined in 23% (n = 9/39) of studies, increased in 41% (n = 16/39) and showed no change in AMR in 36% (n = 14/39). There were no obvious differences between AMR; in setting which used PCV10 vs PCV13, according to time since PCV introduction or by World Bank income status of the respective country. The only study including OM isolates found no change in penicillin resistance. There were few studies on AMR in NPC (four studies), OM (one study) or other isolates (five studies). The results followed similar patterns to IPD isolates.

Conclusions

We observed considerable heterogeneity in the findings between and within studies, e.g. no evidence of reduction in amoxicillin AMR with an increase in macrolides AMR. Reasons for such diverse findings include the period covered by different studies and variation in other pressures towards AMR.

Effectiveness of 10 and 13-valent pneumococcal conjugate vaccines against invasive pneumococcal disease in European children: SpIDnet observational multicentre study

BACKGROUND

Pneumococcal conjugate vaccines covering 10 (PCV10) and 13 (PCV13) serotypes have been introduced in the infant immunization schedule of most European countries in 2010-11. To provide additional real-life data, we measured the effectiveness of PCV10 and PCV13 against invasive pneumococcal disease (IPD) in children of 12 European sites (SpIDnet).

METHODS

We compared the vaccination status of PCV10 and PCV13 serotype IPD (cases) to that of nonPCV13 serotype IPD (controls) reported in 2012-2018. We calculated pooled effectiveness as (1-vaccination odds ratio)*100, and measured effectiveness over time since booster dose.

RESULTS

The PCV13 and PCV10 studies included 2522 IPD cases from ten sites and 486 cases from four sites, respectively. The effectiveness of ≥ 1 PCV13 dose was 84.2% (95 %CI: 79.0-88.1) against PCV13 serotypes (n = 2353) and decreased from 93.1% (87.8-96.1) < 12 months to 85.1% (72.0-92.1) ≥ 24 months after booster dose. PCV13 effectiveness of ≥ 1 dose was 84.7% (55.7-94.7) against fatal PCV13 IPD, 64.5% (43.7-77.6), 83.2% (73.7-89.3) and 85.1% (67.6-93.1) against top serotypes 3, 19A and 1, respectively, and 85.4% (62.3-94.4) against 6C. Serotype 3 and 19A effectiveness declined more rapidly. PCV10 effectiveness of ≥ 1 dose was 84.8% (69.4-92.5) against PCV10 serotypes (n = 370), 27.2% (-187.6 to 81.6) and 85.3% (35.2-96.7) against top serotypes 1 and 7F, 32.5% (-28.3 to 64.5) and -14.4% (-526.5 to 79.1) against vaccine-related serotypes 19A and 6C, respectively.

CONCLUSIONS

PCV10 and PCV13 provide similar protection against IPD due to the respective vaccine serotype groups but serotype-specific effectiveness varies by serotype and vaccine. PCV13 provided individual protection against serotype 3 and vaccine-related serotype 6C IPD. PCV10 effectiveness was not significant against vaccine-related serotypes 19A and 6C. PCV13 effectiveness declined with time after booster vaccination. This multinational study enabled measuring serotype-specific vaccine effectiveness with a precision rarely possible at the national level. Such large networks are crucial for the post-licensure evaluation of vaccines.

Non-invasive pneumococcal pneumonia due to vaccine serotypes: A systematic review and meta-analysis

BACKGROUND

Non-invasive pneumococcal pneumonia causes significant morbidity and mortality in older adults. Understanding pneumococcal sero-epidemiology in adults ≥50 years is necessary to inform vaccination policies and the updating of pneumococcal vaccines.

METHODS

We conducted a systematic review and random-effects meta-analysis to determine the proportion of community-acquired pneumonia (CAP) in people ≥50 years due to pneumococcus and the proportion caused by pneumococcal vaccine serotypes. We searched MEDLINE, EMBASE and PubMed from 1 January 1990 to 30 March 2021. Heterogeneity was explored by subgroup analysis according to a) patient group (stratified versus age) and depth of testing, b) detection/serotyping method, and c) continent. The protocol is registered with PROSPERO (CRD42020192002).

FINDINGS

Twenty-eight studies were included (34,216 patients). In the period 1-5 years after introduction of childhood PCV10/13 immunisation, 18% of CAP cases (95% CI 13-24%) were attributable to pneumococcus, with 49% (43-54%) of pneumococcal CAP due to PCV13 serotypes. The estimated proportion of pneumococcal CAP was highest in one study that used 24-valent serotype-specific urinary-antigen detection (ss-UAD)(30% [28-31%]), followed by studies based on diagnostic serology (28% [24-33%]), PCR (26% [15-37%]), ss-UAD14 (17% [13-22%]), and culture alone (14% [10-19%]). A higher estimate was observed in Europe (26% [21-30%] than North America (11% [9-12%](p<0·001). PCV13-serotype estimates were also influenced by serotyping methods.

INTERPRETATION

Non-invasive pneumococcal CAP and vaccine-type pneumococcal CAP remains a burden in older adults despite widespread introduction of pneumococcal infant immunisation. Studies heavily reliant on ss-UADs restricted to vaccine-type serotypes may overestimate the proportion of potentially vaccine-preventable pneumococcal pneumonia. Sero-epidemiological data from low-income countries are lacking.

Characterization of Streptococcus pneumoniae detected in clinical respiratory tract samples in southern Sweden 2 to 4 years after introduction of PCV13

OBJECTIVE

To determine the serotype distribution and antimicrobial resistance of Streptococcus pneumoniae associated with mucosal infections in patients of all ages, 2 to 4 years after the transition from a 10-valent pneumococcal conjugate vaccine (PCV10) to PCV13 in the childhood immunization programme.

METHODS

Background information and antimicrobial susceptibility data regarding all respiratory tract, middle ear, and conjunctival samples positive for growth of S. pneumoniae (n = 2,131) were collected during 18 months in 2016-2018. Available corresponding bacterial isolates were serotyped by PCR and/or antisera (n = 1,858).

RESULTS

In total, 17% of isolates were covered by PCV13, predominantly represented by serotypes 3 (9%) and 19A (5%). The most common nonvaccine serotypes were 11A (10%), 23B (10%), 15A (6%) and 35F (5%). Isolates exhibiting serotype 15A or 23B were often multidrug-resistant (21%) or penicillin nonsusceptible (38%), respectively.

CONCLUSIONS

The overall proportion of serotype 19A was halved compared to a previous observation period when PCV10 was used (years 2011-2013), suggesting herd protection related to PCV13. The proportion of serotype 3 was, however, unchanged. Despite most nonvaccine serotypes causing mucosal infections have a low invasive potential, certain antibiotic resistant serotypes may pose a clinical problem.

Antibiotic resistance among major pathogens compared to hospital treatment guidelines and antibiotic use in Nordic hospitals 2010-2018

BACKGROUND

The Nordic countries have comparable nationwide antibiotic resistance surveillance systems and individual antibiotic stewardship programmes. The aim of this study was to assess antibiotic resistance among major pathogens in relation to practice guidelines for hospital antibiotic treatment and antibiotic use in Nordic countries 2010-2018.

METHODS

Antibiotic resistance among invasive isolates from 2010-2018 and aggregated antibiotic use were obtained from the European Centre for Disease Prevention and Control. Hospital practice guidelines were obtained from national or regional guidelines.

RESULTS

Antibiotic resistance levels among Escherichia coli and Klebsiella pneumoniae were similar in all Nordic countries in 2018 and low compared to the European mean. Guidelines for acute pyelonephritis varied; 2nd generation cephalosporin (Finland), 3rd generation cephalosporins (Sweden, Norway), ampicillin with an aminoglycoside or aminoglycoside monotherapy (Denmark, Iceland and Norway). Corresponding guidelines for sepsis of unknown origin were 2nd (Finland) or 3rd (Sweden, Norway, Iceland) generation cephalosporins, carbapenems, (Sweden) combinations of penicillin with an aminoglycoside (Norway, Denmark), or piperacillin-tazobactam (all Nordic countries). Methicillin-resistant Staphylococcus aureus rates were 0-2% and empirical treatment with anti-MRSA antibiotics was not recommended in any country. Rates of penicillin non-susceptibility among Streptococcus pneumoniae were low (<10%) except in Finland and Iceland (<15%), but benzylpenicillin was recommended for community-acquired pneumonia in all countries.

CONCLUSION

Despite similar resistance rates among Enterobacteriaceae there were differences in practice guidelines for pyelonephritis and sepsis. National surveillance of antibiotic resistance can be used for comparison and optimization of guidelines and stewardship interventions to preserve the low levels of antibiotic resistance in Nordic countries.

Carbon Source-Dependent Changes of the Structure of Streptococcus pneumoniae Capsular Polysaccharide with Serotype 6F

The structure of the exopolysaccharide capsule of Streptococcus pneumoniae is defined by the genetic arrangement of the capsule operon allowing the unequivocal identification of the pneumococcal serotype. Here, we investigated the environment-dependent composition of the polysaccharide structure of S. pneumoniae serotype 6F. When grown in a chemically defined medium (CDM) with glucose versus galactose, the exopolysaccharide capsule of the serotype 6F strains reveals a ratio of 1/0.6 or 1/0.3 for galactose/glucose in the capsule by ¹H-NMR analyses, respectively. Increased production of the capsule precursor UDP-glucose has been identified by ³¹P-NMR in CDM with glucose. Flow cytometric experiments using monoclonal antibodies showed decreased labelling of Hyp6AG4 (specific for serotype 6A) antibodies when 6F is grown in glucose as compared to galactose, which mirrors the 1H-NMR results. Whole-genome sequencing analyses of serotype 6F isolates suggested that the isolates evolved during two different events from serotype 6A during the time when the 13-valent pneumococcal conjugate vaccine (PCV-13) was introduced. In conclusion, this study shows differences in the capsular structure of serotype 6F strains using glucose as compared to galactose as the carbon source. Therefore, 6F strains may show slightly different polysaccharide composition while colonizing the human nasopharynx (galactose rich) as compared to invasive locations such as the blood (glucose rich).

Whole genome sequencing of macrolide resistant Streptococcus pneumoniae serotype 19A sequence type 416

Background

The resistance of Streptococcus pneumoniae to macrolides is becoming an increasingly important issue and thus it is important to understand the genetics related to adaptation of this species to the widespread use of antibiotics in Europe. The 58 isolates of S. pneumoniae belonging to sequence type (ST) 416 and serotype 19A and to several different phenotypes originated from Italy, Portugal and Czech Republic were thus sequenced on Illumina MiSeq. The aim of the study was to describe genetical origine of isolates, investigate their macrolide resistance and suggest reasons for spread of ST416 in the Czech Republic.

Results

Investigation of genes associated with serotype determined serotype switch between 15B and 19A serotypes and core genome multilocus sequence typing (cgMLST) confirmed the origine of concerned isolates in Netherlands^15B-37 clone. Inspected genomes proved variability of genes associated with the macrolide resistance even within closely genetically relative isolates.

Conclusions

Participation of 19A/ST416 on the spread of Netherlands^15B-37 is accompanied by serotype switch between 19A and 15B serotypes and with acquisition of genes involved in macrolide resistance to the clone that was originally macrolide susceptible. There is evident tendency to interchanging and modifications of these and surrounding genes, that could lead to accelerate spreading of this sequence type in regions with high macrolide consumption.

Recent advances in the epidemiology and prevention of Streptococcus pneumoniae infections

The introduction of pneumococcal conjugate vaccines (PCVs) 7 and 13 into national childhood immunization programs in the US in 2000 and 2010, respectively, proved to be remarkably successful in reducing infant mortality due to invasive pneumococcal disease (IPD), resulting in widespread uptake of these vaccines. Secondary herd protection of non-vaccinated adults against IPD has proven to be an additional public health benefit of childhood immunization with PCVs, particularly in the case of the vulnerable elderly who are at increased risk due to immunosenescence and underlying comorbidity. Despite these advances in pneumococcal immunization, the global burden of pneumococcal disease, albeit of unequal geographic distribution, remains high. Reasons for this include restricted access of children living in many developing countries to PCVs, the emergence of infection due to non-vaccine serotypes of the pneumococcus, and non-encapsulated strains of the pathogen. Emerging concerns affecting the elderly include the realization that herd protection conferred by the current generation of PCVs (PCV7, PCV10, and PCV13) has reached a ceiling in many countries at a time of global population aging, compounded by uncertainty surrounding those immunization strategies that induce optimum immunogenicity and protection against IPD in the elderly. All of the aforementioned issues, together with a consideration of pipeline and pending strategies to improve access to, and serotype coverage of, PCVs, are the focus areas of this review.

Reduction of antimicrobial resistant pneumococci seven years after introduction of pneumococcal vaccine in Iceland

Background

Penicillin non-susceptible (PNSP) and multi-resistant pneumococci have been prevalent in Iceland since early nineties, mainly causing problems in treatment of acute otitis media. The 10-valent protein conjugated pneumococcal vaccine (PHiD-CV) was introduced into the childhood vaccination program in 2011. The aim of the study was to investigate the changes in antimicrobial susceptibility and serotype distribution of penicillin non-susceptible pneumococci (PNSP) in Iceland 2011–2017.

Methods and findings

All pneumococcal isolates identified at the Landspítali University Hospital in 2011–2017, excluding isolates from the nasopharynx and throat were studied. Susceptibility testing was done according to the EUCAST guidelines using disk diffusion with chloramphenicol, erythromycin, clindamycin, tetracycline, trimethoprim/sulfamethoxazole and oxacillin for PNSP screening. Penicillin and ceftriaxone minimum inhibitory concentrations (MIC) were measured for oxacillin resistant isolates using the E-test. Serotyping was done using latex agglutination and/or multiplex PCR. The total number of pneumococcal isolates that met the study criteria was 1,706, of which 516 (30.2%) were PNSP, and declining with time. PNSP isolates of PHiD-CV vaccine serotypes (VT) were 362/516 (70.2%) declining with time, 132/143 (92.3%) in 2011 and 17/54 (31.5%) in 2017. PNSP were most commonly of serotype 19F, 317/516 isolates declining with time, 124/143 in 2011 and 15/54 in 2017. Their number decreased in all age groups, but mainly in the youngest children. PNSP isolates of non PHiD-CV vaccine serotypes (NVT) were 154/516, increasing with time, 11/14, in 2011 and 37/54 in 2017. The most common emerging NVTs in 2011 and 2017 were 6C, 1/143 and 10/54 respectively.

Conclusions

PNSP of VTs have virtually disappeared from children with pneumococcal diseases after the initiation of pneumococcal vaccination in Iceland and a clear herd effect was observed. This was mainly driven by a decrease of PNSP isolates belonging to a serotype 19F multi-resistant lineage. However, emerging multi-resistant NVT isolates are of concern.