Pneumococcal conjugate vaccine failure in children: A systematic review of the literature

Assessing vaccine-induced immunity against pneumococcus, hepatitis A and B over a 9-year follow-up in pediatric liver transplant recipients: A nationwide retrospective study

Pediatric liver transplant recipients are particularly at risk of infections. The most cost-effective way to prevent infectious complications is through vaccination, which can potentially prevent infections due to hepatitis B (HBV) virus, hepatitis A virus (HAV), and invasive pneumococcal diseases. Here, we performed a retrospective analysis of HBV, HAV, and pneumococcal immunity in pediatric liver transplant recipients between January 1, 2009, and December 31, 2020, to collect data on immunization and vaccine serology. A total of 94% (58/62) patients had available vaccination records. At transplant, 90% (45/50) were seroprotected against HBV, 63% (19/30) against HAV, and 78% (18/23) had pneumococcal immunity, but immunity against these 3 pathogens remained suboptimal during the 9-year follow-up. A booster vaccine was administered to only 20% to 40% of patients. Children who had received >4 doses of HBV vaccine and > 2 doses of HAV vaccine pretransplant displayed a higher overall seroprotection over time post-solid organ transplant. Our findings suggest that a serology-based approach should be accompanied by a more systematic follow-up of vaccination, with special attention paid to patients with an incomplete vaccination status at time of transplant.

Robust Immune Response and Protection against Lethal Pneumococcal Challenge with a Recombinant BCG-PspA-PdT Prime/Boost Scheme Administered to Neonatal Mice

Pneumococcal diseases are an important public health problem, with high mortality rates in young children. Although conjugated pneumococcal vaccines offer high protection against invasive pneumococcal diseases, this is restricted to vaccine serotypes, leading to serotype replacement. Furthermore, the current vaccines do not protect neonates. Therefore, several protein-based pneumococcal vaccines have been studied over the last few decades. Our group established a recombinant BCG expressing rPspA-PdT as a prime/rPspA-PdT boost strategy, which protected adult mice against lethal intranasal pneumococcal challenge. Here, we immunized groups of neonate C57/Bl6 mice (6-10) (at 5 days) with rBCG PspA-PdT and a boost with rPspA-PdT (at 12 days). Controls were saline or each antigen alone. The prime/boost strategy promoted an IgG1 to IgG2c isotype shift compared to protein alone. Furthermore, there was an increase in specific memory cells (T and B lymphocytes) and higher cytokine production (IFN-γ, IL-17, TNF-α, IL-10, and IL-6). Immunization with rBCG PspA-PdT/rPspA-PdT showed 100% protection against pulmonary challenge with the WU2 pneumococcal strain; two doses of rPspA-PdT showed non-significant protection in the neonates. These results demonstrate that a prime/boost strategy using rBCG PspA-PdT/rPspA-PdT is effective in protecting neonates against lethal pneumococcal infection via the induction of strong antibody and cytokine responses.

Invasive Pneumococcal Disease After 2 Decades of Pneumococcal Conjugate Vaccine Use

OBJECTIVES

We sought to describe the evolving epidemiology of invasive pneumococcal disease (IPD) among children in Massachusetts, United States, over the last 2 decades during which sequential 7-valent pneumococcal conjugate vaccines (PCV7) and 13-valent PCVs (PCV13) were implemented.

METHODS

Cases of IPD in children aged <18 years were detected between 2002 and 2021 through an enhanced population-based, statewide surveillance system. Streptococcus pneumoniae isolates from normally sterile sites were serotyped and evaluated for antimicrobial susceptibility. IPD incidence rates and rate ratios with 95% confidence intervals (CIs) were calculated.

RESULTS

We identified 1347 IPD cases. Incidence of IPD in children aged <18 years declined 72% over 2 decades between 2002 and 2021 (incidence rate ratios 0.28, 95% CI 0.18-0.45). IPD rates continued to decline after replacement of PCV7 with PCV13 (incidence rate ratios 0.25, 95% CI 0.16-0.39, late PCV7 era [2010] versus late PCV13 era [2021]). During the coronavirus disease 2019 pandemic years, 2020 to 2021, the rate of IPD among children aged <18 years reached 1.6 per 100 000, the lowest incidence observed over the 20 years. In PCV13 era, approximately one-third of the IPD cases in children aged >5 years had at least 1 underlying condition (98, 30.3%). Serotypes 19A and 7F contributed 342 (48.9%) of all cases before implementation of PCV13 (2002-2010). Serotype 3 (31, 8.6%), and non-PCV13 serotypes 15B/C (39, 10.8%), 33F (29, 8.0%), 23B (21, 0.8%), and 35B (17, 4.7%) were responsible for 37.8% of cases in PCV13 era (2011-2021). Penicillin nonsusceptibility continued to decline (9.8% vs 5.3% in pre-/late PCV13 era, P = .003), however has become more common among non-PCV13 serotypes compared with vaccine serotypes (14.8% vs 1.4%, P < .001).

CONCLUSIONS

Robust ongoing surveillance networks are critical for identifying emerging serotypes and development of next-generation vaccine formulations.

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.

Novel pneumococcal capsule type 33E results from the inactivation of glycosyltransferase WciE in vaccine type 33F

The polysaccharide (PS) capsule is essential for immune evasion and virulence of Streptococcus pneumoniae. Existing pneumococcal vaccines are designed to elicit anticapsule antibodies; however, the effectiveness of these vaccines is being challenged by the emergence of new capsule types or variants. Herein, we characterize a newly discovered capsule type, 33E, that appears to have repeatedly emerged from vaccine type 33F via an inactivation mutation in the capsule glycosyltransferase gene, wciE. Structural analysis demonstrated that 33E and 33F share an identical repeat unit backbone [→5)-β-D-Galf2Ac-(1→3)-β-D-Galp-(1→3)-α-D-Galp-(1→3)-β-D-Galf-(1→3)-β-D-Glcp-(1→], except that a galactose (α-D-Galp) branch is present in 33F but not in 33E. Though the two capsule types were indistinguishable using conventional typing methods, the monoclonal antibody Hyp33FM1 selectively bound 33F but not 33E pneumococci. Further, we confirmed that wciE encodes a glycosyltransferase that catalyzes the addition of the branching α-D-Galp and that its inactivation in 33F strains results in the expression of the 33E capsule type. Though 33F and 33E share a structural and antigenic similarity, our pilot study suggested that immunization with a 23-valent pneumococcal PS vaccine containing 33F PS did not significantly elicit cross-opsonic antibodies to 33E. New conjugate vaccines that target capsule type 33F may not necessarily protect against 33E. Therefore, studies of new conjugate vaccines require knowledge of the newly identified capsule type 33E and reliable pneumococcal typing methods capable of distinguishing it from 33F.

Hearing outcomes in children with pneumococcal meningitis in the PCV13 era

INTRODUCTION

Streptococcus pneumoniae, is associated with the highest incidence of post-meningitic SNHL. The exact impact of 13-valent pneumococcal conjugate vaccine (PCV) on pediatric SNHL from pneumococcal meningitis is unknown. We aimed to identify clinical factors associated with post-meningitic SNHL (pmSNHL) from pneumococcal meningitis and describe its rates based on three time periods: pre-PCV, PCV-7 and PCV13 eras.

METHODS

A retrospective case-control study was performed for patients 18 years and younger diagnosed with pneumococcal meningitis from January 1, 2010 to December 31, 2020 at Children's Hospital Colorado. Demographic and clinical risk factors between those with or without SNHL were compared. Detailed hearing outcomes of those with resulting SNHL are described.

RESULTS

23 patients with CSF cultures or Meningitis/Encephalitis Panel positive for pneumococcal meningitis were identified. Twenty patients both survived the infection and had audiologic evaluation. Six patients had pmSNHL, with 50 % affected bilaterally. The rate of pmSNHL from S. pneumoniae in the PCV-13 era at our institution was similar to historical rates from the pre-PCV and PCV-7 eras. Similar proportions of patients with pmSNHL completed PCV vaccination (66.7 %) compared to those without (71.4 %). Non-PCV-13 serotypes were responsible 83 % of patients with pmSNHL versus 57 % of patients without pmSNHL.

CONCLUSIONS

Despite high rates of PCV-13 uptake in our cohort, pmSNHL was still common, severe, and commonly associated with non-PCV-13 serotypes. Non-PCV-13 serotypes may be contributing to the persistently high rate of post-meningitic SNHL and the severity of SNHL. Newer pneumococcal conjugate vaccines with expanded serotypes may help mitigate the SNHL associated with pneumococcal meningitis.

Single priming and booster dose of ten-valent and 13-valent pneumococcal conjugate vaccines and Streptococcus pneumoniae colonisation in children in South Africa: a single-centre, open-label, randomised trial

BACKGROUND

Pneumococcal conjugate vaccine (PCV) immunisation has reduced vaccine-serotype colonisation and invasive pneumococcal disease in South Africa, providing the opportunity to consider transitioning from a two-dose (2 + 1) to one-dose (1 + 1) primary series and a booster dose.

METHODS

In this single-centre, open-label, randomised trial done in South Africa, infants aged 35-49 days without HIV infection, without childhood immunisations except for BCG and polio, and with gestation age at delivery of at least 37 weeks of age, a birthweight of at least 2500 g, and weight of at least 3500 g at the time of enrolment were randomly assigned (1:1:1:1:1:1), through block randomisation (block size of 30), to receive a single priming dose of ten-valent PCV (PCV10) or 13-valent PCV (PCV13) at either 6 weeks (6-week 1 + 1 group) or 14 weeks (14-week 1 + 1 group), compared with two priming doses at 6 weeks and 14 weeks (2 + 1 group), followed by a booster dose at 9 months of age in all groups. The primary objective of the trial has been published previously. We report the secondary objective of the effect of alternative doses of PCV10 and PCV13 on serotype-specific Streptococcus pneumoniae colonisation at 9 months, 15 months, and 18 months of age and a further exploratory analysis in which we assessed non-inferiority of serotype-specific serum IgG geometric mean concentrations 1 month after the booster (10 months of age) and the percentage of participants with serotype-specific IgG titre above the putative thresholds associated with a risk reduction of serotype-specific colonisation between the 1 + 1 and 2 + 1 groups for both vaccines. Non-inferiority was established if the lower limit of the 95% CI for the difference between the proportion of participants (1 + 1 group vs 2 + 1 group) above the putative thresholds was greater than or equal to -10%. All analyses were done in the modified intention-to-treat population, which included all participants who received PCV10 or PCV13 according to assigned randomisation group and for whom laboratory results were available. The trial is registered with ClinicalTrials.gov, NCT02943902.

FINDINGS

1564 nasopharyngeal swabs were available for molecular serotyping from 600 infants who were enrolled (100 were randomly assigned to each of the six study groups) between Jan 9 and Sept 20, 2017. There was no significant difference in the prevalence of overall or non-vaccine serotype colonisation between all PCV13 or PCV10 groups. PCV13 serotype colonisation was lower at 15 months of age in the 14-week 1 + 1 group than in the 2 + 1 group (seven [8%] of 85 vs 17 [20%] of 87; odds ratio 0·61 [95% CI 0·38-0·97], p=0·037), but no difference was seen at 9 months (nine [11%] of 86 vs ten [11%] of 89; 0·92 [0·60-1·55], p=0·87) or 18 months (nine [11%] of 85 vs 11 [14%] of 87; 0·78 [0·45-1·22], p=0·61). Compared with the PCV13 2 + 1 group, both PCV13 1 + 1 groups did not meet the non-inferiority criteria for serotype-specific anti-capsular antibody concentrations above the putative thresholds purportedly associated with risk reduction for colonisation; however, the PCV10 14-week 1 + 1 group was non-inferior to the PCV10 2 + 1 group.

INTERPRETATION

The serotype-specific colonisation data reported in this study together with the primary immunogenicity endpoints of the control trial support transitioning to a reduced 1 + 1 schedule in South Africa. Ongoing monitoring of colonisation should, however, be undertaken immediately before and after transitioning to a PCV 1 + 1 schedule to serve as an early indicator of whether PCV 1 + 1 could lead to an increase in vaccine-serotype disease.

FUNDING

The Bill & Melinda Gates Foundation.

Vaccine effectiveness of the 7-valent and 13-valent pneumococcal conjugate vaccines in Canada: An IMPACT study

We used an indirect cohort analysis in children under 5 years-old from 2002 to 2018 to examine vaccine effectiveness (VE) of the 7-valent pneumococcal conjugate vaccine (PCV) (3 + 1 doses in most regions) and the 13-valent PCV (2 + 1 doses in all regions) against invasive pneumococcal disease (IPD) caused by vaccine serotypes in children in Canada. Cases were identified from the Canadian Immunization Monitoring Program ACTive (IMPACT), a national active surveillance network of 12 tertiary care pediatric hospitals that represent about 90% of tertiary care hospital beds in Canada. There were 1477 children evaluated for PCV7 VE and 489 for PCV13 VE. PCV7 VE in children with vaccination up to date for their age was 96% (95% CI: 67-99%) after a single dose and 95% (95% CI: 92-97%) after ≥2 doses. The VE was 91% (95% CI: 85-94%) in children who had received doses but were not up to date for their age. PCV13 VE in children with vaccinations up to date for their age was 55% (95% CI: 28-72%) after ≥2 doses. The PCV13-vaccine serotypes causing breakthrough IPD in children up to date for their age with 2+ doses of PCV13 were 3 (13/27, 48.2%),19A (11/27, 40.7%), and 19F (3/27, 11.1%). When serotype 3 and 19A were excluded, the VE of PCV13 against the remaining vaccine serotypes was 89% (95% CI: 64-97%) in children with ≥2 doses. The lower VE of PCV13 may be due to lower effectiveness against serotypes 3 and 19A, which could be influenced by the change in dosing schedule from 4 to 3 total doses with the introduction of PCV13, combined with vaccine uptake of 80%. However, PCV13 still provides the benefit of protection against more serotypes than PCV7, and good VE against all serotypes except 3 and 19A.

The effect of human vaccination behaviour on strain competition in an infectious disease: An imitation dynamic approach

Strain competition plays an important role in shaping the dynamics of multiple pathogen outbreaks in a population. Competition may lead to exclusion of some pathogens, while it may influence the invasion of an emerging mutant in the population. However, little emphasis has been given to understand the influence of human vaccination choice on pathogen competition or strain invasion for vaccine-preventable infectious diseases. Coupling game dynamic framework of vaccination choice and compartmental disease transmission model of two strains, we explore invasion and persistence of a mutant in the population despite having a lower reproduction rate than the resident one. We illustrate that higher perceived strain severity and lower perceived vaccine efficacy are necessary conditions for the persistence of a mutant strain. The numerical simulation also extends these invasion and persistence analyses under asymmetric cross-protective immunity of these strains. We show that the dynamics of this cross-immunity model under human vaccination choices is determined by the interplay of parameters defining the cross-immune response function, perceived risk of infection, and vaccine efficacy, and it can exhibit invasion and persistence of mutant strain, even complete exclusion of resident strain in the regime of sufficiently high perceived risk. We conclude by discussing public health implications of the results, that proper risk communication in public about the severity of the disease is an important task to reduce the chance of mutant invasion. Thus, understanding pathogen competitions under social interactions and choices may be an important component for policymakers for strategic decision-making.

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.

From Genetics to Epigenetics: Top 4 Aspects for Improved SARS-CoV-2 Vaccine Designs as Paradigmatic Examples

This literature review described the genetic and biochemical factors that may have been overlooked in the formulation of vaccines and that most likely underlie possible issues with mass vaccination.

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

Vaccination with the 13-valent conjugated pneumococcal disease (PCV13) has reduced invasive pneumococcal disease (IPD), but there have been reports of vaccine failures. We performed a prospective study in children aged 2–59 months who received diagnoses of IPD during January 2012–June 2016 in 3 pediatric hospitals in Catalonia, Spain, a region with a PCV13 vaccination coverage of 63%. We analyzed patients who had been age-appropriately vaccinated but who developed IPD caused by PCV13 serotypes. We detected 24 vaccine failure cases. The serotypes involved were 3 (16 cases); 19A (5 cases); and 1, 6B, and 14 (1 case each). Cases were associated with children without underlying conditions, with complicated pneumonia (OR 6.65, 95% CI 1.91–23.21), and with diagnosis by PCR (OR 5.18, 95% CI 1.84–14.59). Vaccination coverage should be increased to reduce the circulation of vaccine serotypes. Continuous surveillance of cases of IPD using both culture and PCR to characterize vaccine failures is necessary.

Properties of Mucoid Serotype 3 Streptococcus pneumoniae From Children in China

Objective

To investigate the characteristics of hosts, antimicrobial susceptibility, and molecular epidemiology of mucoid serotype 3 Streptococcus pneumoniae (S. pneumoniae) isolated from children in China.

Method

S. pneumoniae isolates collected between January 2016 and December 2019 were analyzed. S. pneumoniae isolates with mucoid phenotype were selected visually, and serotype 3 isolates were confirmed by Quellung reaction. The antimicrobial susceptibility was measured by E-test. Multilocus sequence typing was used for clonal analysis.

Results

Twenty (3.04%) isolates of mucoid serotype 3 S. pneumoniae were identified from 657 clinical isolates, and all of them were noninvasive strains. The mean age of the hosts was 5.69 ± 3.28 years. The isolates included: 50.0% from the dissected tonsil or adenoid tissue in children with obstructive sleep apnea-hypopnea syndrome, 45.0% from sputum or bronchial lavages in children with pneumonia, and 5.0% from vaginal secretions of one patient with vulvovaginitis. All isolates were susceptible to penicillin, cefuroxime, ceftriaxone, meropenem, vancomycin, levofloxacin, trimethoprim/sulfamethoxazole, and rifampin but resistant to erythromycin. Sequence type (ST)505 and its clonal complex (CC) were the main genotypes (95%). Antimicrobial susceptibility of ST180 and ST505 were compared, and the minimum inhibitory concentration (MIC) of ST505 isolates was significantly higher than that of ST180 for tetracycline, trimethoprim/sulfamethoxazole, and meropenem.

Conclusions

Mucoid serotype 3 Streptococcus pneumoniae can be isolated from various body parts, among which the respiratory system is the most common. It can cause noninvasive infection in children, and it has high susceptibility to a variety of antibiotics, especially β-lactams, but is resistant to macrolides. CC505 is the novel clonal complex found in China, which may be related to the worldwide mainstream clonal complex (CC180) but has its own biological characteristics.

Effect of a 2+1 schedule of ten-valent versus 13-valent pneumococcal conjugate vaccine on pneumococcal carriage: Results from a randomised controlled trial in Vietnam

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) generate herd protection by reducing nasopharyngeal (NP) carriage. Two PCVs, PCV10 and PCV13, have been in use for over a decade, yet there are few data comparing their impact on carriage. Here we report their effect on carriage in a 2+1 schedule, compared with each other and with unvaccinated controls.

METHODS

Data from four groups within a parallel, open-label randomised controlled trial in Ho Chi Minh City contribute to this article. Three groups were randomised to receive a 2+1 schedule of PCV10 (n = 250), a 2+1 schedule of PCV13 (n = 251), or two doses of PCV10 at 18 and 24 months (controls, n = 197). An additional group (n = 199) was recruited at 18 months to serve as controls from 18 to 24 months. NP swabs collected at 2, 6, 9, 12, 18, and 24 months were analysed (blinded) for pneumococcal carriage. This study aimed to determine if PCV10 and PCV13 have a differential effect on pneumococcal carriage, a secondary outcome of the trial. We also describe the serotype distribution among unvaccinated participants.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01953510.

FINDINGS

Compared with unvaccinated controls, a 2+1 schedule of PCV10 reduced PCV10-type carriage by 45-62% from pre-booster through to 24 months of age, and a 2+1 schedule of PCV13 reduced PCV13-type carriage by 36-49% at 12 and 18 months of age. Compared directly with each other, there were few differences between the vaccines in their impact on carriage. Vaccine serotypes accounted for the majority of carriage in unvaccinated participants.

INTERPRETATION

Both PCV10 and PCV13 reduce the carriage of pneumococcal vaccine serotypes. The introduction of either vaccine would have the potential to generate significant herd protection in this population.

FUNDING

National Health and Medical Research Council of Australia, Bill & Melinda Gates Foundation.

Dynamic changes in paediatric invasive pneumococcal disease after sequential switches of conjugate vaccine in Belgium: a national retrospective observational study

BACKGROUND

Ten-valent and 13-valent pneumococcal conjugate vaccines (PCVs) have shown important benefits by decreasing invasive pneumococcal disease caused by vaccine serotypes. Belgium had an uncommon situation with sequential use of PCV7, PCV13, and PCV10 in the childhood vaccination programmes between 2007 and 2018. We aimed to analyse the changes in incidence of invasive pneumococcal disease and serotype distribution in children throughout this period.

METHODS

Streptococcus pneumoniae isolates were obtained from patients with invasive pneumococcal disease in Belgium between 2007 and 2018 by the national laboratory-based surveillance. Paediatric invasive pneumococcal disease incidence, serotype distribution, and antimicrobial susceptibility were analysed in periods during which PCV7 (2009-10), PCV13 (2013-14), both PCV13 and PCV10 (2015-16), and PCV10 (2017-18) were used. Incidence rates and trends were compared. Vaccination status was collected. For a subset of serotype 19A isolates, multilocus sequence type was identified.

FINDINGS

After a decrease in PCV7 serotype invasive pneumococcal disease was observed during the PCV7 period, total paediatric invasive pneumococcal disease incidence significantly declined during the PCV13 period (-2·6% monthly, p<0·0001). During the PCV13-PCV10 period (2015-16), the lowest mean in paediatric invasive pneumococcal disease incidence was achieved, but the incidence increased again during the PCV10 period (2017-18), especially in children younger than 2 years (+1·7% monthly; p=0·028). This increase was mainly due to a significant rise in serotype 19A invasive pneumococcal disease incidence in the PCV10 period compared with the PCV13 period (p<0·0001), making serotype 19A the predominant serotype in paediatric invasive pneumococcal disease in the PCV10 period. Genetic diversity within the 2017-18 serotype 19A collection was seen, with two predominant clones, ST416 and ST994, that were infrequently observed before PCV10 introduction. In 2018, among children younger than 5 years with invasive pneumococcal disease who were correctly vaccinated, 37% (37 of 100) had PCV13 serotype invasive pneumococcal disease, all caused by serotype 19A and serotype 3.

INTERPRETATION

After a significant decrease during the PCV13 period, paediatric invasive pneumococcal disease incidence increased again during the PCV10 period. This observation mainly resulted from a significant increase of serotype 19A cases. During the PCV10 period, dominant serotype 19A clones differed from those detected during previous vaccine periods. Whether changes in epidemiology resulted from the vaccine switch or also from natural evolution remains to be further elucidated.

FUNDING

The Belgian National Reference is funded by the Belgian National Institute for Health and Disability Insurance and the whole genome sequencing by an investigator-initiated research grant from Pfizer.

Immunotherapy targeting the Streptococcus pyogenes M protein or streptolysin O to treat or prevent influenza A superinfection

Viral infections complicated by a bacterial infection are typically referred to as coinfections or superinfections. Streptococcus pyogenes, the group A streptococcus (GAS), is not the most common bacteria associated with influenza A virus (IAV) superinfections but did cause significant mortality during the 2009 influenza pandemic even though all isolates are susceptible to penicillin. One approach to improve the outcome of these infections is to use passive immunization targeting GAS. To test this idea, we assessed the efficacy of passive immunotherapy using antisera against either the streptococcal M protein or streptolysin O (SLO) in a murine model of IAV-GAS superinfection. Prophylactic treatment of mice with antiserum to either SLO or the M protein decreased morbidity compared to mice treated with non-immune sera; however, neither significantly decreased mortality. Therapeutic use of antisera to SLO decreased morbidity compared to mice treated with non-immune sera but neither antisera significantly reduced mortality. Overall, the results suggest that further development of antibodies targeting the M protein or SLO may be a useful adjunct in the treatment of invasive GAS diseases, including IAV-GAS superinfections, which may be particularly important during influenza pandemics.

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).

Serotype distribution of Streptococcus pneumonia in children with invasive disease in Turkey: 2015-2018

Objectives: To determine the serotype distribution of pneumococcus causing invasive pneumococcal disease (meningitidis, bacteremia and empyema) in children in Turkey, and to observe potential changes in this distribution in time to guide effective vaccine strategies.

Methods: We surveyed S. pneumoniae with conventional bacteriological techniques and with real-time polymerase chain reaction (RT-PCR) in samples of cerebrospinal fluid (CSF), blood and pleural fluid. S. pneumoniae strains were isolated from 33 different hospitals in Turkey, which are giving health services to approximately 60% of the Turkish population.

Results: A total of 167 cases were diagnosed with invasive pneumococcal disease between 2015 and 2018. We diagnosed 52 (31.1%) patients with meningitis, 104 (62.2%) patients with bacteremia, and 11 (6.6%) patients with empyema. Thirty-three percent of them were less than 2 years old and 56% less than 5 years old. Overall PCV13 serotypes accounted for 56.2% (94/167). The most common serotypes were 19 F (11.9%), 1 (10.7%) and 3 (10.1%).

Conclusions: Besides the increasing frequency of non-vaccine serotypes, vaccine serotypes continue to be a problem for Turkey despite routine and high-rate vaccination with PCV13 and significant reduction reported for the incidence of IPD in young children. Since new candidate pneumococcal conjugate vaccines with more serotype antigens are being developed, continuing IPD surveillance is a significant source of information for decision-making processes on pneumococcal vaccination.

Severe suppurative otitis media due to Streptococcus pneumoniae serotype 19A in a fully vaccinated infant by age

The routine use of pneumococcal conjugated vaccines (PCVs) in childhood has significantly reduced the frequency of invasive pneumococcal diseases (IPDs). Serotype replacement has occurred, resulting in an increase in nonvaccine serotypes. Despite this changing profile, both invasive and noninvasive cases continue to be seen with strains within the scope of PCV coverage. Although older children with comorbid disease are described as a risky group for vaccine insufficiency, vaccine failure patterns should be described in detail.

Pneumococcal Conjugate Vaccine Breakthrough Infections: 2001-2016

BACKGROUND

Most countries use 3-dose pneumococcal conjugate vaccine (PCV) schedules; a 4-dose (3 primary and 1 booster) schedule is licensed for US infants. We evaluated the invasive pneumococcal disease (IPD) breakthrough infection incidence in children receiving 2 vs 3 primary PCV doses with and without booster doses (2 + 1 vs 3 + 1; 2 + 0 vs 3 + 0).

METHODS

We used 2001-2016 Active Bacterial Core surveillance data to identify breakthrough infections (vaccine-type IPD in children receiving ≥1 7-valent pneumococcal conjugate vaccine [PCV7] or 13-valent pneumococcal conjugate vaccine [PCV13] dose) among children aged <5 years. We estimated schedule-specific IPD incidence rates (IRs) per 100 000 person-years and compared incidence by schedule (2 + 1 vs 3 + 1; 2 + 0 vs 3 + 0) using rate differences (RDs) and incidence rate ratios.

RESULTS

We identified 71 PCV7 and 49 PCV13 breakthrough infections among children receiving a schedule of interest. PCV13 breakthrough infection rates were higher in children aged <1 year receiving the 2 + 0 (IR: 7.8) vs 3 + 0 (IR: 0.6) schedule (incidence rate ratio: 12.9; 95% confidence interval: 4.1-40.4); PCV7 results were similar. Differences in PCV13 breakthrough infection rates by schedule in children aged <1 year were larger in 2010-2011 (2 + 0 IR: 18.6; 3 + 0 IR: 1.4; RD: 16.6) vs 2012-2016 (2 + 0 IR: 3.6; 3 + 0 IR: 0.2; RD: 3.4). No differences between schedules were detected in children aged ≥1 year for PCV13 breakthrough infections.

CONCLUSIONS

Fewer PCV breakthrough infections occurred in the first year of life with 3 primary doses. Differences in breakthrough infection rates by schedule decreased as vaccine serotypes decreased in circulation.

Nasopharyngeal pneumococcal carriage in healthy Turkish children after 13-valent conjugated pneumococcal vaccine implementation in the national immunization program

BACKGROUND

In Turkey, pneumococcal conjugated vaccine (PCV) was introduced to the national immunization program as PCV7 in 2008, and was replaced with PCV13 in 2011. The aims of this study were to investigate the effects of PCV13 on nasopharyngeal pneumococcal carriage (NPC) by determining the serotype distribution, and to identify risk factors for carriage, in healthy Turkish children.

METHODS

This prospective study was conducted on 500 healthy children aged 0-13 years between April and November 2014. Nasopharyngeal swab samples were taken, and molecular method for capsular serotyping was performed by multiplex PCR.

RESULTS

Of 500 children, 43.4% were unvaccinated with a PCV (7- or 13-valent), 56.6% were vaccinated and The NPC rate was found to be 9.8%. Of 49 positive Streptococcus pneumoniae isolates, 26 (53%) were PCV13 vaccine strains (VSs), and 17 (34.7%) were non-VS. Six isolates (12.2%) were not typeable by the method applied. The most common serotypes detected were serotype 3 (18.3%), serotype 19F (14.2%), serotype 6A/B (8.1%), serotype 11A (8.1%), and serotype 15B (8.1%). The total coverage rate of the PCV13 serotypes was 60.4%.

CONCLUSION

A significant decrease in carriage rate was detected within three years after the introduction of PCV13 in Turkey. However, the nasopharyngeal carriage of PCV13 strains was found to be interestingly high.

Invasive Pneumococcal Disease in Children's Hospitals: 2014-2017

BACKGROUND

The 13-valent pneumococcal conjugate vaccine (PCV13) was licensed in the United States in 2010. We describe invasive pneumococcal disease (IPD) in children at 8 children's hospitals in the US from 2014 to 2017.

METHODS

Children with IPD occurring from 2014 to 2017 were identified from a prospective study. Demographic and clinical data, including results of any immune evaluation along with the number and dates of previous pneumococcal conjugate vaccines administered, were recorded on case report forms. Isolate serotypes were determined in a central laboratory. Pneumococcal conjugate vaccine doses were counted if IPD occurred ≥2 weeks after a dose.

RESULTS

PCV13 serotypes accounted for 23.9% (115 out of 482) of IPD isolates from 2014 to 2017. Serotypes 3, 19A, and 19F accounted for 91% of PCV13 serotypes. The most common non-PCV13 serotypes were 35B, 23B, 33F, and 22F. An underlying condition was significantly (P < .0001) more common in children with IPD due to non-PCV13 serotypes (200 out of 367, 54.5%) than for children with PCV13 serotypes (27 out of 115, 23.5%). An immune evaluation was undertaken in 28 children who received ≥2 PCV13 doses before IPD caused by a PCV13 serotype. Only 1 was found to have an immunodeficiency.

CONCLUSIONS

PCV13 serotypes (especially serotypes 3, 19A, and 19F) continue to account for nearly a quarter of IPD in US children 4 to 7 years after PCV13 was introduced. Underlying conditions are more common in children with non-PCV13 serotype IPD. Immune evaluations in otherwise healthy children with PCV13 serotype IPD despite receiving ≥2 PCV13 doses did not identify an immunodeficiency.

Immunogenicity and reactogenicity of ten-valent versus 13-valent pneumococcal conjugate vaccines among infants in Ho Chi Minh City, Vietnam: a randomised controlled trial

Background

Few data are available to support the choice between the two currently available pneumococcal conjugate vaccines (PCVs), ten-valent PCV (PCV10) and 13-valent PCV (PCV13). Here we report a head-to-head comparison of the immunogenicity and reactogenicity of PCV10 and PCV13.

Methods

In this parallel, open-label, randomised controlled trial, healthy infants from two districts in Ho Chi Minh City, Vietnam, were randomly allocated (in a 3:3:5:4:5:4 ratio), with use of a computer-generated list, to one of six infant PCV schedules: PCV10 in a 3 + 1 (group A), 3 + 0 (group B), 2 + 1 (group C), or two-dose schedule (group D); PCV13 in a 2 + 1 schedule (group E); or no infant PCV (control; group F). Blood samples were collected from infants between 2 months and 18 months of age at various timepoints before and after PCV doses and analysed (in a blinded manner) by ELISA and opsonophagocytic assay. The trial had two independent aims: to compare vaccination responses between PCV10 and PCV13, and to evaluate different schedules of PCV10. In this Article, we present results pertaining to the first aim. The primary outcome was the proportion of infants with an IgG concentration of at least 0·35 μg/mL for the ten serotypes common to the two vaccines at age 5 months, 4 weeks after the two-dose primary vaccination series (group C vs group E, per protocol population). An overall difference among the schedules was defined as at least seven of ten serotypes differing in the same direction at the 10% level. We also assessed whether the two-dose primary series of PCV13 (group E) was non-inferior at the 10% level to a three-dose primary series of PCV10 (groups A and B). This trial is registered with ClinicalTrials.gov, number NCT01953510.

Findings

Of 1424 infants screened between Sept 30, 2013, and Jan 9, 2015, 1201 were allocated to the six groups: 152 (13%) to group A, 149 (12%) to group B, 250 (21%) to group C, 202 (17%) to group D, 251 (21%) to group E, and 197 (16%) to group F. 237 (95%) participants in group C (PCV10) and 232 (92%) in group E (PCV13) completed the primary vaccination series and had blood draws within the specified window at age 5 months, at which time the proportion of infants with IgG concentrations of at least 0·35 μg/mL did not differ between groups at the 10% level for any serotype (PCV10–PCV13 risk difference −2·1% [95% CI −4·8 to −0·1] for serotype 1; −1·3% [–3·7 to 0·6] for serotype 4; −3·4% [–6·8 to −0·4] for serotype 5; 15·6 [7·2 to 23·7] for serotype 6B; −1·3% [–3·7 to 0·6] for serotype 7F; −1·6% [–5·1 to 1·7] for serotype 9V; 0·0% [–2·7 to 2·9] for serotype 14; −2·1% [–5·3 to 0·9] for serotype 18C; 0·0% [–2·2 to 2·3] for serotype 19F; and −11·6% [–18·2 to −4·9] for serotype 23F). At the same timepoint, two doses of PCV13 were non-inferior to three doses of PCV10 for nine of the ten shared serotypes (excluding 6B). Reactogenicity and serious adverse events were monitored according to good clinical practice guidelines, and the profiles were similar in the two groups.

Interpretation

PCV10 and PCV13 are similarly highly immunogenic when used in 2 + 1 schedule. The choice of vaccine might be influenced by factors such as the comparative magnitude of the antibody responses, price, and the relative importance of different serotypes in different settings.

Funding

National Health and Medical Research Council of Australia, and Bill & Melinda Gates Foundation.

Genome-wide analysis of Streptococcus pneumoniae serogroup 19 in the decade after the introduction of pneumococcal conjugate vaccines in Australia

The decline in invasive pneumococcal disease (IPD), following the introduction of the 7-valent pneumococcal conjugate vaccination (PCV-7), was tempered by emergence of non-vaccine serotypes, particularly 19A. In Australia, three years after PCV-7 was replaced by PCV-13, containing 19A and 19F antigens, serogroup 19 was still a prominent cause of IPD in children under five. In this study we examined the evolution of serogroup 19 before and after introduction of paediatric vaccines in New South Wales (NSW), Australia. Genomes of 124 serogroup 19 IPD isolates collected before (2004) and after introduction of PCV-7 (2008) and PCV-13 (2014), from children under five in NSW, were analysed. Eleven core genome sequence clusters (cgSC) and 35 multilocus sequence types (ST) were identified. The majority (78/124) of the isolates belonged to four cgSCs: cgSC7 (ST199), cgSC11 (ST320), cgSC8 (ST63) and cgSC9 (ST2345). ST63 and ST2345 were exclusively serotype 19A and accounted for its predominantly intermediate penicillin resistance; these two clusters first appeared in 2008 and largely disappeared after introduction of PCV-13. Serogroup 19 was responsible for the highest proportion of vaccine failures in NSW. Relatively low immunogenicity of serogroup 19 antigens and Australia's three-dose vaccine schedule could affect the population dynamics of this serogroup.

Adult pneumococcal vaccination: advances, impact, and unmet needs

PURPOSE OF REVIEW

Preventing pneumonia in the elderly and individuals with comorbidities is an unmet clinical need. Streptococcus pneumoniae is the commonest bacterial cause of pneumonia, and we summarize recent findings regarding current S. pneumoniae vaccines, and debate their efficacy and cost-effectiveness in risk groups. We also discuss potential future vaccine strategies such as protein antigen vaccines.

RECENT FINDINGS

Current vaccination with pneumococcal polysaccharide vaccine does not prevent S. pneumoniae pneumonia. Vaccination with pneumococcal conjugated vaccine (PCV) prevents nasopharyngeal colonization, but although PCV13 has recently been shown to prevent S. pneumoniae pneumonia in adults, its overall efficacy was relatively low. The results of cost-effectiveness studies of PCV vaccination in adults are variable with some showing this is a cost-effective strategy, whereas others have not. The lack of cost-effectiveness is predominantly because of the current cost of the PCV vaccine and the existing herd immunity effect from childhood PCV vaccination on vaccine serotypes.

SUMMARY

S. pneumoniae pneumonia is a vaccine-preventable disease but remains a common cause of morbidity and mortality. Advances in vaccination using approaches that induce serotypes-independent immunity and are immunogenic in high-risk groups are required to reduce the burden of disease because of S. pneumoniae.

Rapid increase in non-vaccine serotypes causing invasive pneumococcal disease in England and Wales, 2000-17: a prospective national observational cohort study

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) have substantially reduced the incidence of invasive pneumococcal disease caused by vaccine serotypes; however, replacement disease with non-PCV serotypes remains a concern. We describe the population effect of the seven-valent and 13-valent PCVs (PCV7 and PCV13) on invasive pneumococcal disease in England and Wales.

METHODS

Using national invasive pneumococcal disease surveillance data for 2016/17, we compared incidence rate ratios (IRRs) against pre-PCV13 (2008/09-2009/10) and pre-PCV7 (2000/01-2005/06) baselines. We also estimated the number of invasive pneumococcal disease cases prevented since the introduction of PCVs.

FINDINGS

In 2016/17, overall invasive pneumococcal disease incidence (9·87 cases per 100 000; 5450 cases) across all age groups was 37% lower (IRR 0·63, 95% CI 0·60-0·65) than pre-PCV7 incidence (14·79 per 100 000; 8167 cases) and 7% lower (0·93; 0·89-0·97) than pre-PCV13 incidence (10·13 per 100 000; 5595 cases). By 2016/17, PCV7-type invasive pneumococcal disease incidence across all age groups had decreased by 97% (0·24 per 100 000; 0·03, 0·02-0·04) compared with the pre-PCV7 period, whereas additional PCV13-type invasive pneumococcal disease decreased by 64% (1·66 per 100 000; 0·36, 0·32-0·40) since the introduction of PCV13. Invasive pneumococcal disease incidence due to non-PCV13 serotypes doubled (7·97 per 100 000; 1·97, 1·86-2·09) since the introduction of PCV7, and accelerated since 2013/14-especially serotypes 8, 12F, and 9N, which were responsible for more than 40% of invasive pneumococcal disease cases by 2016/17. Invasive pneumococcal disease incidence in children younger than 5 years remained stable since 2013/14, with nearly all replacement disease occurring in adults. We estimated 38 366 invasive pneumococcal disease cases were prevented in the 11 years since the introduction of PCV7.

INTERPRETATION

Both PCV7 and PCV13 have had a major effect in reducing the burden of invasive pneumococcal disease in England and Wales; however, rapid increases in some non-PCV13 serotypes are compromising the benefits of the programme.

FUNDING

Public Health England.

Plasma cell and serum antibody responses to influenza vaccine in preterm and full-term infants

BACKGROUND

Preterm (PT) infants are at greater risk for severe influenza infection and experience decrements in long-term antibody responses to vaccines. This may related to defects in antibody secreting cell (ASC) generation.

OBJECTIVE

To investigate the relationships among the frequencies of influenza-specific antibody secreting cells, ASC numbers and subsets, and antibody responses to influenza vaccines (IV) among PT and full-term (FT) infants.

DESIGN/METHODS

We enrolled 11 former PT (≤32weeks' gestation, ≤1500 g' birth weight) and 11FT infants, 6-17months of age, receiving their first influenza immunizations. Infants received two doses of inactivated trivalent (T)IV or quadrivalent (Q)IV during the 2012-2013 and 2013-2014 influenza seasons, respectively, at 0 and 28days, and blood was drawn at 0, 10, 35, and 56days and 9months. Vaccine-specific antibody was measured by hemagglutination inhibition (HAI) at 0 and 56days and 9months, vaccine-specific ASC numbers by enzyme linked immunospot (ELISPOT) at 10 and 35days, and ASC subsets by flow cytometry at 0, 10 and 35days.

RESULTS

PT infants had post-vaccine HAI titers to all 4 vaccine strains at least equal to FT infants at 56days and 9months after beginning immunization. Influenza-specific ASC ELISPOT responses at 35days were higher among PT than FT infants (median 100 v. 30 per 10⁶ PBMC, p=0.04). ASC numbers at 35days were positively correlated with serum HAI titers at 56days (ρ=0.50-0.80). There were no statistical differences between PT and FT infants in the frequency of five ASC subsets and no specific ASC subset correlated with durability of serum antibody titers.

CONCLUSIONS

Influenza-specific ASC numbers in both FT and PT infants correlated with peak antibody titers, but ASC subsets did not correlate with durability of antibody response.

Colonization with 19F and other pneumococcal conjugate vaccine serotypes in children in St. Louis, Missouri, USA

BACKGROUND

The epidemiology of nasopharyngeal (NP) pneumococcal carriage varies with geography and has changed in response to pneumococcal conjugate vaccine (PCV): a low prevalence (3% or less of colonizing isolates) of colonization by vaccine-type (VT) pneumococcal serotypes after PCV introduction has been reported. The primary goal of this study was to determine the VT serotype prevalence of NP pneumococcal colonization of children residing in the St. Louis, MO, USA metropolitan area following introduction of the 13-valent PCV in 2010. The secondary goal of this study was to identify characteristics associated with NP pneumococcal carriage of any serotype.

METHODS

Between July 2013 and April 2016, we enrolled 397 healthy children, aged 0-17years, who required sedation for procedures or minor surgeries at St. Louis Children's Hospital. NP swabs were collected after sedation or anesthesia and cultured for pneumococcus. Vaccine records were obtained from primary care providers or from state immunization databases. Parents/guardians completed a questionnaire to provide demographics, past medical history and household characteristics.

RESULTS

Of the 88 pneumococcal isolates recovered from 84 colonized subjects (21.2% of all enrolled subjects; 95% CI 17.2-25.2%), 16 were VT. Eleven isolates were serotype 19F (12.5%), four (4.5%) were 6A and one (1.1%) was 19A. Prevalence of VT among colonizing isolates was thus 18.2% (CI 10.1-26.1%) in our cohort, despite complete PCV vaccination in 87% of colonized children. Factors associated with pneumococcal colonization by any serotype included younger age and daycare attendance.

CONCLUSION

Children in St. Louis exhibit a higher prevalence of VT serotypes among pneumococcal carriage isolates than has been reported in other areas in the US, demonstrating the necessity of ongoing surveillance of local epidemiology and providing evidence that serotype 19F can remain prevalent in a pediatric population despite high vaccine uptake.

Potential Usefulness of Streptococcus pneumoniae Extracellular Membrane Vesicles as Antibacterial Vaccines

The secretion of extracellular membrane vesicles (EMVs) is a common phenomenon that occurs in archaea, bacteria, and mammalian cells. The EMVs of bacteria play important roles in their virulence, biogenesis mechanisms, and host cell interactions. Bacterial EMVs have recently become the focus of attention because of their potential as highly effective vaccines that cause few side effects. Here, we isolated the EMVs of Streptococcus pneumoniae and examined their potential as new vaccine candidates. Although the S. pneumoniae bacteria were highly pathogenic in a mouse model, the EMVs purified from these bacteria showed low pathological activity both in cell culture and in mice. When mice were injected intraperitoneally with S. pneumoniae EMVs and then challenged, they were protected from both the homologous strain and another pathogenic serotype of S. pneumoniae. We also identified a number of proteins that may have immunogenic activity and may be responsible for the immune responses by the hosts. These results suggest that S. pneumoniae EMVs or their individual immunogenic antigens may be useful as new vaccine agents.