Epidemiology of non-vaccine serotypes of Streptococcus pneumoniae before and after universal administration of pneumococcal conjugate vaccines

Streptococcus pneumoniae serotype distribution in low- and middle-income countries of South Asia: Do we need to revisit the pneumococcal vaccine strategy?

S. pneumoniae serotypes responsible for pneumococcal disease differ with respect to disease severity, invasiveness, antimicrobial susceptibility, geographies, immunization history, age groups, and with time. Although PCVs have blunted the pneumococcal disease burden, they are plagued with numerous challenges, especially the emergence of NVTs. In this review, we show that there are diverse serotypes, especially NVTs, responsible for causing pneumococcal diseases in LMICs of South Asia across different studies conducted between 2012 and 2024. We propose that pharmaceutical/biotech companies should tailor/customize the PCVs as per the region-specific serotype prevalence based on surveillance data. Furthermore, protein-based vaccines, or WCVs, have been explored and can serve as viable alternatives to address the limitations associated with PCVs. However, robust studies are warranted in different geographies to demonstrate its efficacy and safety in clinical trials as well as the real-world effectiveness of these promising candidates.

A global epidemic serotype 14 Streptococcus pneumoniae switching to non-vaccine types

Streptococcus pneumoniae infection is a leading cause of bacterial pneumonia worldwide, contributing to both invasive pneumococcal diseases and non-invasive diseases. Following the introduction of pneumococcal conjugate vaccines (PCV7, PCV10, and PCV13), a significant decrease in the prevalence of vaccine-type pneumococci has been observed, while the prevalence of non-vaccine-type (NVT) pneumococci has increased. This shift has been evident in both disease incidence and nasopharyngeal carriage. Serotype switching refers to the alteration or exchange of the serotype-related cps gene locus that has been flagged globally as serotypes of concern. In this study, we collected 166 S. pneumoniae clinical isolates and analyzed the serotypes of isolates to evaluate vaccine effectiveness. Additionally, we identified multidrug-resistant NVT S. pneumoniae isolates that recently emerged within the epidemic CC876 complex, a pandemic serotype 14 clone. More importantly, we identified a serotype 15B/ST4749 strain, which might have been generated through a serotype-switch event from serotype 14/ST4749. Mapping the genomic recombination sites within the serotype 15B/ST4749 progeny revealed a donated fragment encompassing cps, pbp1a, and additional key factors, including the DNA uptake-related gene comC. More importantly, as a strain that is already prevalent, the novel NVT strain possesses the potential to become a global pandemic strain.IMPORTANCEThe study employed high-throughput sequencing to analyze Streptococcus pneumoniae isolates from Xiamen Children's Hospital, China, to evaluate vaccine effectiveness in light of serotype changes and documented the occurrence of a serotype switch (from 14 to 15B) between vaccine-type and non-vaccine-type serotypes in the ST4749 strain. This observation indicates a genomic recombination and adaptive response of S. pneumoniae under selective pressure exerted by vaccination, offering novel insights into strategies for the prevention and control of S. pneumoniae and the optimization of vaccine deployment.

A population-based study on the burden of hospitalized pediatric pneumococcal disease in Taiwan before and after the introduction of 13-valent pneumococcal conjugate vaccine into the childhood immunization program in 2015

BACKGROUND

To estimate the burden of invasive pneumococcal disease, non-bacteremic pneumococcal pneumonia, and acute otitis media before and after inclusion of the 13-valent pneumococcal vaccine (PCV13) into Taiwan's Childhood Immunization Program in 2015.

METHODS

Episodes of eligible children aged < 18 years hospitalized with invasive pneumococcal disease, non-bacteremic pneumococcal pneumonia, or acute otitis media between 1 January 2011 and 31 December 2019 were identified from the National Health Insurance Research Database. Annual hospitalized incidence rate, case fatality rate, and healthcare resource utilization and costs were estimated. Incidence time trends were assessed with interrupted time series analyses.

RESULTS

1,284 invasive pneumococcal disease episodes, 25,074 non-bacteremic pneumococcal pneumonia episodes, and 23,139 acute otitis media episodes were identified. The overall annual incidence rates of invasive pneumococcal disease, non-bacteremic pneumococcal pneumonia, and acute otitis media were 3.31, 64.61, and 59.62 episodes per 100,000 person-years, respectively. Interrupted time series analyses results showed a significantly lower baseline incidence rate (incidence rate ratio [IRR]:0.58, p-value = 0.001) for invasive pneumococcal disease, and significantly higher baseline incidence rate (IRR:1.17, p-value < 0.001) for non-bacteremic pneumococcal pneumonia in the post-PCV13 period. Baseline incidence rates between the two periods were comparable for acute otitis media. A significant increase in trend of incidence rate was observed for all three diseases. Case fatality rate was 1.79%, 0.09%, and 0.00% for invasive pneumococcal disease, non-bacteremic pneumococcal pneumonia, and acute otitis media, respectively. Median length of hospitalization per inpatient visit was comparable between the two periods for invasive pneumococcal disease and non-bacteremic pneumococcal pneumonia, but significantly shorter in the post-PCV13 period for acute otitis media. In the post-PCV13 period, average total costs per episode was lower for invasive pneumococcal disease and non-bacteremic pneumococcal pneumonia, but higher for acute otitis media.

CONCLUSIONS

Residual clinical and economic burden of pneumococcal diseases remained substantial after PCV13 inclusion into Taiwan's Childhood Immunization Program. To further reduce the disease burden among children, additional research to investigate the cause of increasing trends of hospitalized invasive pneumococcal disease, non-bacteremic pneumococcal pneumonia and acute otitis media in the post-PCV13 era will be required.

Safety, reactogenicity, and immunogenicity of a novel 24-valent pneumococcal vaccine candidate in healthy, pneumococcal vaccine-naïve Japanese adults: A phase 1 randomized dose-escalation trial

BACKGROUND

The burden of pneumococcal diseases remains high in Japan. Pn-MAPS24v is a novel MAPS-based vaccine containing complexes of 24 serotype-specific polysaccharides (PS), non-covalently coupled with fusion protein 1 (CP1). This study evaluated the safety and immunogenicity of different dose levels of Pn-MAPS24v, administered in Japanese adults either subcutaneously (SC) or intramuscularly (IM).

METHODS

In this phase 1, dose-escalation, observer-blind trial conducted in Japan, 54 pneumococcal vaccine-naïve adults aged 20-49 years (stage 1), and 72 adults aged 65-85 years (stage 2) were sequentially enrolled. In stage 1, participants were randomized 1:1 (SC:IM) to receive a single Pn-MAPS24v dose at one of the dose levels (1 μg, 2 μg, or 5 μg per PS). In stage 2, participants were randomized 3:1 (Pn-MAPS24v:23-valent pneumococcal polysaccharide vaccine [PPSV23]) and 1:1 (SC:IM) to receive a single dose of either Pn-MAPS24v (one of three dose levels), or PPSV23. Solicited adverse events (AEs) were collected through 7 days post-vaccination, and treatment-emergent AEs (TEAEs) up to 1 month post-vaccination. Serotype-specific opsonophagocytic activity titers and immunoglobulin G (IgG) concentrations, as well as anti-CP1 IgG concentrations were measured before and 1 month post-vaccination.

RESULTS

No safety or reactogenicity concerns were identified in any age category across groups. No grade 3-4 TEAEs, serious AEs, or deaths were reported. Regardless of the age category, dose level, administration route, or study vaccine, the frequency of reported TEAEs was low and all vaccine-related TEAEs were mild. Pain, tenderness, and fatigue were the most frequently reported solicited AEs. One month post-vaccination, Pn-MAPS24v induced serotype-specific immune responses that were comparable or higher than those elicited by PPSV23. The immune responses were similar after SC and IM administration.

CONCLUSION

Pn-MAPS24v showed an acceptable safety profile and was immunogenic after SC and IM administration, therefore supporting the further development of Pn-MAPS24v in Japan.

CLINICALTRIALS

gov: NCT04265911.

A phase 3, single-arm, open-label study to evaluate the safety, tolerability, and immunogenicity of a 15-valent pneumococcal conjugate vaccine, V114, in a 3+1 regimen in healthy infants in South Korea (PNEU-PED-KOR)

There is an ongoing burden of pneumococcal disease in children despite the use of pneumococcal conjugate vaccines (PCVs). This phase 3, open-label, single-arm, multisite, descriptive study was designed to evaluate the safety and immunogenicity of a 3 + 1 regimen of V114 (VAXNEUVANCE™), a 15-valent PCV, in South Korean infants and toddlers. Adverse events (AEs) were reported for 14 d following any vaccination, and throughout the study period for serious AEs. Serotype-specific immunoglobulin G (IgG) response rates (proportion of participants meeting an IgG threshold value of ≥0.35 μg/mL) and geometric mean concentrations (GMCs) for the 15 serotypes at 30 d postdose 3 (PD3) and at 30 d postdose 4 (PD4) were evaluated as endpoints. Healthy infants enrolled at 42-90 d after birth were vaccinated with V114 (N = 57). The most commonly reported AEs were those solicited in the trial. The majority of reported AEs were transient and of mild or moderate intensity. Few serious AEs were reported; none were vaccine related. No participants died nor discontinued the study vaccine because of an AE. V114 was immunogenic for all 15 serotypes contained in the vaccine, as assessed by IgG response rates at 30 d PD3 and IgG GMCs at 30 d PD3 and at 30 d PD4. V114 was well tolerated and immunogenic when administered as a 3 + 1 regimen in healthy South Korean infants and toddlers.

Intranasal influenza-vectored vaccine expressing pneumococcal surface protein A protects against Influenza and Streptococcus pneumoniae infections

Streptococcus pneumoniae and influenza A virus (IAV) are significant agents of pneumonia cases and severe respiratory infections globally. Secondary bacterial infections, particularly by Streptococcus pneumoniae, are common in IAV-infected individuals, leading to critical outcomes. Despite reducing mortality, pneumococcal vaccines have high production costs and are serotype specific. The emergence of new circulating serotypes has led to the search for new prevention strategies that provide a broad spectrum of protection. In this context, vaccination using antigens present in all serotypes, such as Pneumococcal Surface Protein A (PspA), can offer broad coverage regardless of serotype. Employing the reverse genetics technique, our research group developed a recombinant influenza A H1N1 virus that expresses PspA (Flu-PspA), through the replacement of neuraminidase by PspA. This virus was evaluated as a bivalent vaccine against infections caused by influenza A and S. pneumoniae in mice. Initially, we evaluated the Flu-PspA virus's ability to infect cells and express PspA in vitro, its capacity to multiply in embryonated chicken eggs, and its safety when inoculated in mice. Subsequently, the protective effect against influenza A and Streptococcus pneumoniae lethal challenge infections in mice was assessed using different immunization protocols. Analysis of the production of antibodies against PspA4 protein and influenza, and the binding capacity of anti-PspA4 antibodies/complement deposition to different strains of S. pneumoniae were also evaluated. Our results demonstrate that the Flu-PspA virus vaccine efficiently induces PspA protein expression in vitro, and that it was able to multiply in embryonated chicken eggs even without exogenous neuraminidase. The Flu-PspA-based bivalent vaccine was demonstrated to be safe, stimulated high titers of anti-PspA and anti-influenza antibodies, and protected mice against homosubtypic and heterosubtypic influenza A and S. pneumoniae challenge. Moreover, an efficient binding of antibodies and complement deposition on the surface of pneumococcal strains ascribes the broad-spectrum vaccine response in vivo. In summary, this innovative approach holds promise for developing a dual-protective vaccine against two major respiratory pathogens.

Advances in the pathogenesis and treatment of pneumococcal meningitis

Streptococcus pneumoniae is a common pathogen associated with community-acquired bacterial meningitis, characterized by high morbidity and mortality rates. While vaccination reduces the incidence of meningitis, many survivors experience severe brain damage and corresponding sequelae. The pathogenesis of pneumococcal meningitis has not been fully elucidated. Currently, meningitis requires bacterial disruption of the blood - brain barrier, a process that involves the interaction of bacterial surface components with host cells and various inflammatory responses. This review delineates the global prevalence, pathogenesis, and treatment strategies of pneumococcal meningitis. The objective is to enhance the thorough comprehension of the clinical manifestations and biological mechanisms of the disease, thereby enabling more efficient prevention, diagnosis, and therapeutic interventions.

Fourier transform infrared spectroscopy for Streptococcus pneumoniae capsular serotype classification in pediatric patients with invasive infections

Invasive pneumococcal disease (IPD) is a major cause of morbidity and mortality worldwide, particularly in the pediatric population (children and infants), with high rates of hospitalization and death. This study aimed to create and validate a classifier for Streptococcus pneumoniae serotyping using Fourier-transform infrared (FT-IR) spectroscopy as a rapid alternative to the classical serotyping technique. In this study, a database comprising 76 clinical isolates, including 18 serotypes (predominantly serotypes 19A, 6C, and 3) of S. pneumoniae from pediatric patients with IPD, was tested at a tertiary pediatric hospital in southern Brazil during 2016-2023. All isolates were previously serotyped using the Quellung reaction, and 843 FT-IR spectra were obtained to create a classification model using artificial neural network (ANN) machine learning. After the creation of this classifier, internal validation was performed using 384 spectra as the training dataset and 459 as the testing dataset, resulting in a predictive accuracy of 98% for serotypes 19A, 6, 3, 14, 18C, 22F, 23A, 23B, 33F, 35B, and 9N. In this dataset, serotypes 10A/16F, 15ABC, and 7CF could not be differentiated and were, therefore, grouped as labels. FT-IR is a promising, rapid, and low-cost method for the phenotypic classification of S. pneumoniae capsular serotypes. This methodology has significant implications for clinical and epidemiological practice, improving patient management, monitoring infection trends, and developing new vaccines.

High prevalence of 19A pneumococcal serotype carriage during the COVID-19 pandemic in Brazil

INTRODUCTION

Streptococcus pneumoniae colonization patterns are influenced by host and environmental factors, which may be related to Invasive Pneumococcal Disease (IPD). Interestingly, COVID-19 pandemic witnessed a decline in the incidence of IPDs. Investigations with diligent data collection on the prevalence of nasopharyngeal colonization and associated serotypes during this unique period can yield novel insights. The aim of the current study was to assess the prevalence of S. pneumoniae carriage among children and adults who have sought care at emergency departments with suspected COVID-19.

METHODS

In this cross-sectional study, adults and children presenting with signs and symptoms likely associated with COVID-19 in two outpatient clinics in Southern Brazil were invited to participate. RT-PCR with a comprehensive molecular panel for pneumococcal identification of the 21 most prevalent serotypes in Latin America was performed on all enrolled subjects. Prevalence of pneumococcal carriage was assessed in the age groups (< 2, ≥ 2-5, ≥ 5-11, ≥ 11-18, ≥ 18-60, ≥ 60).

RESULTS

A total of 1644 subjects were included in the study. Pneumococcal carriage was detected by PCR testing in 14.9% (245/1,644), and serotype identification occurred in 42.0% (103/245) of the participants, with a total frequency of 111. The most frequent serotype identified was 19A (25.2%, n = 28/111), followed by 6C/6D (17.1%, n = 19/111), and 23A (11.7%, n = 13/111), also highlighting the high frequency of non-vaccine serotypes found across all age groups.

DISCUSSION

19A serotype, as well other most frequent serotypes identified are not covered by the PCV-10 in a community setting where PCV-10 is widely available. This finding reinforces the need for continuous surveillance to determine the impact of pneumococcal vaccination and guide public health decision-making. High 19A serotype prevalence is critical in the decision-making process for electing the best options for pneumococcal conjugate vaccines.

Unraveling the full impact of SPD_0739: a key effector in S. pneumoniae iron homeostasis

Streptococcus pneumoniae is a common member of the nasopharynx commensal microflora and the leading etiological agent of bacterial pneumonia in young children and aging adults. SPD_0739, a highly expressed lipoprotein, is the predicted substrate-binding component of an ABC transporter linked to the uptake of nucleosides and heme by independent studies (named PnrA or Spbhp-37, respectively). Here, we demonstrate that SPD_0739 binds heme in vitro and contributes to the bacterial binding to hemoglobin. A ∆spd_0739 strain exhibited growth attenuation that was relieved by the inactivation of the piuBCDA transporter. Knocking out spd_0739 in the wild type, or the ΔpiuBCDA strain resulted in heme accumulation, higher sensitivity to heme toxicity, and a small growth reduction compared to medium supplemented with a nucleoside mixture. In addition, spd_0739 loss results in higher iron- and heme-related gene expression and lower H2O2 production. Altogether, the data are consistent with a role in nucleoside import and show that SPD_0739 does not import heme. Instead, it indirectly influences iron and heme metabolism, linking nucleosides and iron status in S. pneumoniae.

IMPORTANCE

S. pneumoniae obtains growth essential iron from hemoglobin and other host hemoproteins. Still, the bacterial mechanisms involved are only partially understood, and there are inconsistent reports regarding the function of several transporters implicated in iron uptake. In this study, we clarified the role of PnrA/Spbhp-37, a ligand-binding protein previously linked to nucleoside or heme by different studies. We present data supporting a role in nucleoside scavenging rather than heme import and reveal that PnrA/Spbhp-37 modulates iron and heme uptake, likely by influencing the nucleoside cellular pool. Hence, this work provides a new understanding of a process critical to the pathophysiology of a significant human pathogen. Moreover, PnrA/Spbhp-37 is an abundant and immunogenic surface protein that is highly conserved. Hence, this study also clarifies the function of a promising vaccine target.

Semi-purified Antimicrobial Proteins from Oyster Hemolymph Inhibit Pneumococcal Infection

Pneumococcal infections caused by Streptococcus pneumoniae are a leading cause of morbidity and mortality globally, particularly among children. The ability of S. pneumoniae to form enduring biofilms makes treatment inherently difficult, and options are further limited by emerging antibiotic resistance. The discovery of new antibiotics, particularly those with antibiofilm activity, is therefore increasingly important. Antimicrobial proteins and peptides (AMPs) from marine invertebrates are recognised as promising pharmacological leads. This study determined the in vitro antibacterial activity of hemolymph and unique protein fractions from an Australian oyster (Saccostrea glomerata) against multi-drug-resistant S. pneumoniae. We developed a successful method for hemolymph extraction and separation into 16 fractions by preparative HPLC. The strongest activity was observed in fraction 7: at 42 µg/mL protein, this fraction was bactericidal to S. pneumoniae and inhibited biofilm formation. Proteomic analysis showed that fraction 7 contained relatively high abundance of carbonic anhydrase, cofilin, cystatin B-like, and gelsolin-like proteins, while surrounding fractions, which showed lower or no antibacterial activity, contained these proteins in lower abundance or not at all. This work supports traditional medicinal uses of oysters and contributes to further research and development of novel hemolymph/AMP-based treatments for pneumococcal infections.

Cost-Effectiveness Analysis of Pneumococcal Vaccines in the Pediatric Population: A Systematic Review

Objectives: Pneumococcal disease, caused by Streptococcus pneumoniae, is the leading cause of mortality in children worldwide. The tremendous direct cost of hospital admissions and significant indirect costs from productivity loss contribute considerably to its economic burden, with vaccination being the only efficient protection against the illness. Our study aims to summarize the cost-effectiveness of the pneumococcal conjugate vaccine (PCV) implemented in the pediatric population. Methods: Employing the online databases PubMed, Embase, and Medline, we looked for economic evaluations from 2018 until March 2024. The Incremental Cost-Effectiveness Ratios (ICER) and Quality-Adjusted Life Years (QALY) were the primary outcomes for measuring the cost-effectiveness of PCVs. A 28-item CHEERS 2022 checklist was applied to assess the quality of the collected studies. Results: Of the 16 papers found, 9/16 discussed the lower-valent vaccines (PCV13, PCV10) and 7/16 examined the higher-valent vaccines (PCV20, PCV15). PCV13 and PCV10 involved greater costs and generated more QALY compared to no vaccination. Both PCV15 and PCV20 averted substantial healthcare costs and yielded greater quality of life than PCV13. Additionally, PCV20 was a dominant strategy compared to PCV15. Conclusions: Utilizing PCV13 is a very cost-effective option compared to not getting vaccinated. Transitioning from PCV13 to PCV20 would result in higher QALY gain and more cost-saving than switching to PCV15.

Vaccines for the Elderly and Vaccination Programs in Europe and the United States

The share of the elderly population is growing worldwide as life expectancy increases. Immunosenescence and comorbidities increase infectious diseases' morbidity and mortality in older adults. Here, we aimed to summarize the latest findings on vaccines for the elderly against herpes zoster, influenza, respiratory syncytial virus (RSV), COVID-19, and pneumococcal disease and to examine vaccine recommendation differences for this age group in Europe and the United States. PubMed was searched using the keywords "elders" and "vaccine" alongside the disease/pathogen in question and paraphrased or synonymous terms. Vaccine recommendations were also sought in the European and US Centers for Disease Control and Prevention databases. Improved vaccines, tailored for the elderly, mainly by using novel adjuvants or by increasing antigen concentration, are now available. Significant differences exist between immunization policies, especially between European countries, in terms of the recipient's age, number of doses, vaccination schedule, and implementation (mandatory or recommended). Understanding the factors that influence the immune response to vaccination in the elderly may help to design vaccines that offer long-term protection for this vulnerable age group. A consensus-based strategy in Europe could help to fill the gaps in immunization policy in the elderly, particularly regarding vaccination against RSV and pneumococcus.

Cost-effectiveness of an in-development adult-formulated 21-valent pneumococcal conjugate vaccine in US adults aged 50 years or older

Indirect effects of childhood pneumococcal conjugate vaccines (PCV) have diminished the cost-effectiveness of current adult vaccine recommendations. An in-development adult-formulated 21-valent pneumococcal conjugate vaccine (PCV21) may play a critical role in reducing pneumococcal illness by targeting a larger number of serotypes responsible for adult pneumococcal infections. This study assesses the cost-effectiveness of PCV21 in US adults aged 50 years or older compared with currently recommended pneumococcal vaccines, from both the societal and healthcare perspectives. A Markov model evaluated the lifetime cost-effectiveness of PCV21 (given at age 50 years only, at ages 50/65 years, and risk-based at ages < 65 years plus age-based at age 65 years) compared to no vaccination and to currently recommended pneumococcal vaccines given either as currently recommended or routinely at ages 50/65 years. The analysis was conducted in hypothetical Black and non-Black cohorts aged 50 years or older, with and without considering childhood pneumococcal vaccination indirect effects. Model parameters were based on US data. Parameter uncertainty was assessed using 1-way and probabilistic sensitivity analyses. From the societal perspective, PCV21 at ages 50/65 years compared to PCV21 at age 50 years cost $7,410 per quality adjusted life year (QALY) gained in Black cohort analyses and $85,696/QALY gained in the non-Black cohort; PCV21 at ages 50/65 years had the most favorable public health outcomes. From the healthcare perspective, compared to no vaccination, PCV21 at age 50 years cost $46,213/QALY gained in the Black cohort and $86,629/QALY in non-Blacks. All other strategies were dominated in both cohorts and from both perspectives. When considering childhood pneumococcal vaccination indirect effects, costs of PCV21 at ages 50/65 years remained less than $140,000/QALY gained from the societal perspective in both populations. PCV21 is potentially cost-effective compared to currently approved pneumococcal vaccines in adults aged 50 years or older from both the societal and healthcare perspectives.

Safety, tolerability and immunogenicity of a novel 24-valent pneumococcal vaccine in toddlers: A phase 1 randomized controlled trial

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) significantly reduced pneumococcal disease burden. Nevertheless, alternative approaches for controlling more serotypes are needed. Here, the safety, tolerability, and immunogenicity of a 24-valent (1/2/3/4/5/6A/6B/7F/8/9N/9V/10A/11A/12F/14/15B/17F/18C/19A/19F/20B/22F/23F/33F) pneumococcal vaccine based on Multiple Antigen-Presenting System (MAPS) technology (Pn-MAPS24v) was assessed in toddlers.

METHODS

In this phase 1, blinded, dose-escalation, active-controlled multicenter study conducted in the United States (September/2020-April/2022), 12-15-month-old toddlers primed with three doses of 13-valent PCV (PCV13) were randomized 3:2 to receive a single dose of one of three Pn-MAPS24v dose levels (1 μg/2 μg/5 μg per polysaccharide) or PCV13 intramuscularly. Reactogenicity (within 7 days), treatment-emergent adverse events (TEAEs, within 180 days), serious/medically attended adverse events (SAEs/MAAEs, within 180 days), and immunogenicity (serotype-specific anti-capsular polysaccharide immunoglobulin G [IgG] and opsonophagocytic activity [OPA] responses at 30 days post-vaccination) were assessed.

RESULTS

Of 75 toddlers enrolled, 74 completed the study (Pn-MAPS24v 1 μg/2 μg/5 μg: 15/14/16, PCV13: 29). Frequencies of local (60 %/67 %/31 %) and systemic events (67 %/67 %/75 %) in the Pn-MAPS24v 1 μg/2 μg/5 μg and the PCV13 (55 %, 79 %) groups were in similar ranges. TEAEs were reported by 47 %/40 %/63 % of Pn-MAPS24v 1 μg/2 μg/5 μg recipients and 52 % of PCV13 recipients. No vaccine-related SAE was reported. At 30 days post-vaccination, for each of the 13 common serotypes, ≥93 % of participants in each group had IgG concentrations ≥0.35 μg/mL; >92 % had OPA titers ≥lower limit of quantitation (LLOQ), except for serotype 1 (79 %). For 7/11 unique serotypes (2/8/9N/11A/17F/22F/33F), at all dose levels, ≥78 % of Pn-MAPS24v recipients in each group had IgG concentrations ≥0.35 μg/mL and 80 %-100 % had OPA titers ≥LLOQ.

CONCLUSIONS

In 12-15-month-old toddlers, a single dose of Pn-MAPS24v showed an acceptable safety profile, regardless of dose level; AEs were reported at similar frequencies by Pn-MAPS24v and PCV13 recipients. Pn-MAPS24v elicited IgG and OPA responses to all common and most unique serotypes. These results support further clinical evaluation in infants.

Serotype-Dependent Inhibition of Streptococcus pneumoniae Growth by Short-Chain Fatty Acids

Streptococcus pneumoniae (pneumococcus) is an opportunistic pathogen that can cause severe infectious diseases such as pneumonia, meningitis, and otitis media. Despite the availability of antibiotics and pneumococcal vaccines against some invasive serotypes, pneumococcal infection remains a tremendous clinical challenge due to the increasing frequency of infection by antimicrobial resistant, nonencapsulated, and/or non-vaccine serotype strains. Short-chain fatty acids (SCFAs), which are produced at various mucosal sites in the body, have potent antimicrobial activity, including inhibition of pathogen growth and/or bacterial biofilm formation. In this study, we investigated the antimicrobial activity of SCFAs (acetate, propionate, and butyrate) against various serotypes pneumococci. Propionate generally inhibited the growth of S. pneumoniae serotypes included in the pneumococcal conjugate vaccine (PCV) 13, except for serotypes 3 and 7F, though butyrate and acetate showed no or low inhibition, depending on the serotypes. Of note, butyrate showed strong inhibition against serotype 3, the most prevalent invasive strain since the introduction of the PCV. No SCFAs showed inhibitory effects against serotype 7F. Remarkably, the nonencapsulated pneumococcal strain had more sensitivity to SCFAs than encapsulated parental strains. Taken together, these results suggest that propionate showing the most potent inhibition of pneumococcal growth may be used as an alternative treatment for pneumococcal infection, and that butyrate could be used against serotype 3, which is becoming a serious threat.

Memory Th17 cell-mediated protection against lethal secondary pneumococcal pneumonia following influenza infection

Streptococcus pneumoniae (Sp) frequently causes secondary pneumonia after influenza A virus (IAV) infection, leading to high morbidity and mortality worldwide. Concomitant pneumococcal and influenza vaccination improves protection against coinfection but does not always yield complete protection. Impaired innate and adaptive immune responses have been associated with attenuated bacterial clearance in influenza virus-infected hosts. In this study, we showed that preceding low-dose IAV infection caused persistent Sp infection and suppression of bacteria-specific T-helper type 17 (Th17) responses in mice. Prior Sp infection protected against subsequent IAV/Sp coinfection by improving bacterial clearance and rescuing bacteria-specific Th17 responses in the lungs. Furthermore, blockade of IL-17A by anti-IL-17A antibodies abrogated the protective effect of Sp preinfection. Importantly, memory Th17 responses induced by Sp preinfection overcame viral-driven Th17 inhibition and provided cross-protection against different Sp serotypes following coinfection with IAV. These results indicate that bacteria-specific Th17 memory cells play a key role in providing protection against IAV/Sp coinfection in a serotype-independent manner and suggest that a Th17-based vaccine would have excellent potential to mitigate disease caused by coinfection. IMPORTANCE Streptococcus pneumoniae (Sp) frequently causes secondary bacterial pneumonia after influenza A virus (IAV) infection, leading to increased morbidity and mortality worldwide. Current pneumococcal vaccines induce highly strain-specific antibody responses and provide limited protection against IAV/Sp coinfection. Th17 responses are broadly protective against Sp single infection, but whether the Th17 response, which is dramatically impaired by IAV infection in naïve mice, might be effective in immunization-induced protection against pneumonia caused by coinfection is not known. In this study, we have revealed that Sp-specific memory Th17 cells rescue IAV-driven inhibition and provide cross-protection against subsequent lethal coinfection with IAV and different Sp serotypes. These results indicate that a Th17-based vaccine would have excellent potential to mitigate disease caused by IAV/Sp coinfection.

Molecular Epidemiology of Streptococcus pneumoniae Detected in Hospitalized Pediatric Acute Respiratory Infection Cases in Central Vietnam

Streptococcus pneumoniae is the major bacterial pathogen causing high pneumonia morbidity and mortality in children <5 years of age. This study aimed to determine the molecular epidemiology of S. pneumoniae detected among hospitalized pediatric ARI cases at Khanh Hoa General Hospital, Nha Trang, Vietnam, from October 2015 to September 2016 (pre-PCV). We performed semi-quantitative culture to isolate S. pneumoniae. Serotyping, antimicrobial susceptibility testing, resistance gene detection and multi-locus sequence typing were also performed. During the study period, 1300 cases were enrolled and 413 (31.8%) S. pneumoniae were isolated. School attendance, age <3 years old and prior antibiotic use before admission were positively associated with S. pneumoniae isolation. Major serotypes were 6A/B (35.9%), 19F (23.7%) and 23F (12.7%), which accounted for 80.3% of vaccine-type pneumococci. High resistance to Clarithromycin, Erythromycin and Clindamycin (86.7%, 85%, 78.2%) and the mutant drug-resistant genes pbp1A (98.1%), pbp2b (98.8%), pbp2x (99.6%) ermB (96.6%) and mefA (30.3%) were detected. MLST data showed high genetic diversity among the isolates with dominant ST 320 (21.2%) and ST 13223 (19.3%), which were mainly found in Vietnam. Non-typeables accounted for most of the new STs found in the study. Vaccine-type pneumococcus and macrolide resistance were commonly detected among hospitalized pediatric ARI cases.

Childhood Bacterial Meningitis Surveillance in Southern Vietnam: Trends and Vaccination Implications From 2012 to 2021

Background

This retrospective hospital-based surveillance aimed to assess the epidemiology, causative pathogens trend, and serotypes distribution of pneumococcal meningitis among children aged under 5 years with bacterial meningitis in Southern Vietnam after the introduction of pentavalent vaccine in the Expanded Program on Immunization (EPI).

Methods

From 2012 to 2021, cerebrospinal fluid samples were collected from children aged under 5 years with suspected bacterial meningitis at Children's Hospitals 1 and 2 in Ho Chi Minh City. Probable bacterial meningitis (PBM) cases were identified using biochemistry and cytology. Real-time polymerase chain reaction was used to confirm cases of confirmed bacterial meningitis (CBM) caused by Streptococcus pneumoniae, Haemophilus influenzae, or Neisseria meningitidis. Streptococcus pneumoniae serotyping was performed.

Results

Of the 2560 PBM cases, 158 (6.2%) were laboratory-confirmed. The CBM proportion decreased during the 10-year study and was associated with age, seasonality, and permanent residence. Streptococcus pneumoniae was the most common pathogen causing bacterial meningitis (86.1%), followed by H influenzae (7.6%) and N meningitidis (6.3%). The case-fatality rate was 8.2% (95% confidence interval, 4.2%-12.2%). Pneumococcal serotypes 6A/B, 19F, 14, and 23F were the most prevalent, and the proportion of pneumococcal meningitis cases caused by the 10-valent pneumococcal conjugate vaccine (PCV) serotypes decreased from 96.2% to 57.1% during the PCV eras.

Conclusions

Streptococcus pneumoniae is the most frequent causative agent of bacterial meningitis in children aged under 5 years in Southern Vietnam over the last decade. Policymakers may need to consider introducing PCVs into the EPI to effectively prevent and control bacterial meningitis.

Safety, tolerability, and immunogenicity of V114 pneumococcal vaccine compared with PCV13 in a 2+1 regimen in healthy infants: A phase III study (PNEU-PED-EU-2)

BACKGROUND

This phase III study evaluated safety, tolerability, and immunogenicity of V114 (15-valent pneumococcal conjugate vaccine) in healthy infants. V114 contains all 13 serotypes in PCV13 and additional serotypes 22F and 33F.

METHODS

Healthy infants were randomized to two primary doses and one toddler dose (2+1 regimen) of V114 or PCV13 at 3, 5, and 12 months of age; diphtheria, tetanus, pertussis (DTaP), inactivated poliovirus (IPV), Haemophilus influenzae type b (Hib), hepatitis B (HepB) vaccine was administered concomitantly. Adverse events (AEs) were collected on Days 1-14 following each vaccination. Serotype-specific anti-pneumococcal immunoglobulin G (IgG) was measured 30 days post-primary series, immediately prior to toddler dose, and 30 days post-toddler dose. Primary objectives included non-inferiority of V114 to PCV13 for 13 shared serotypes and superiority of V114 to PCV13 for serotypes 22F and 33F.

RESULTS

1191 healthy infants were randomized to V114 (n = 595) or PCV13 (n = 596). Proportions of participants with solicited AEs and serious AEs were comparable between groups. V114 met non-inferiority criteria for 13 shared serotypes, based on difference in proportions with serotype-specific IgG ≥0.35 μg/mL (lower bound of two-sided 95% confidence interval [CI] >-10.0) and IgG geometric mean concentration (GMC) ratios (lower bound of two-sided 95% CI >0.5) at 30 days post-toddler dose. V114 met superiority criteria for serotypes 22F and 33F, based on response rates (lower bound of two-sided 95% CI >10.0) and IgG GMC ratios (lower bound of two-sided 95% CI >2.0) at 30 days post-toddler dose. Antibody responses to DTaP-IPV-Hib-HepB met non-inferiority criteria, based on antigen-specific response rates.

CONCLUSION

A two-dose primary series plus toddler dose of V114 was well-tolerated in healthy infants. Compared with PCV13, V114 provided non-inferior immune responses to 13 shared serotypes and superior immune responses to additional serotypes 22F and 33F.

Effectiveness of the 23-valent pneumococcal polysaccharide vaccine against community-acquired pneumonia in older individuals after the introduction of childhood 13-valent pneumococcal conjugate vaccine: A multicenter hospital-based case-control study in Japan

BACKGROUND

In the era of childhood pneumococcal conjugate vaccine (PCV) immunization, especially 13-valent pneumococcal conjugate vaccine (PCV13) immunization, serotype replacement of Streptococcus pneumoniae and herd immunity in adults have been reported worldwide. Therefore, continuous evaluation of the effectiveness of the pneumococcal vaccine in adults is crucial because vaccine effectiveness may change owing to these factors. The purpose of this study was to evaluate the effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPSV23) against all-cause pneumonia and pneumococcal pneumonia in older individuals with community-acquired pneumonia (CAP) after the introduction of childhood PCV13 in Japan, a topic that has remained largely unexplored.

METHODS

We evaluated pneumococcal vaccine effectiveness in this multicenter, matched case-control study conducted in hospitals and clinics. Cases included patients (aged ≥ 65 years) newly diagnosed with CAP between October 2016 and September 2019. A maximum of five non-pneumonia control patients matched for sex, school grade, date of outpatient visit, and medical institution were selected for each case. Conditional logistic regression models were used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) of pneumococcal vaccines for the occurrence of all-cause CAP and pneumococcal CAP.

RESULTS

The analysis included 740 individuals (142 patients and 598 controls). The median age of participants was 75 years (men: 54%). The adjusted OR for pneumococcal vaccination against all-cause CAP was 1.31 (95% CI: 0.84-2.06), while that for PPSV23 vaccination in the previous 5 years was 1.33 (95% CI: 0.85-2.09). The adjusted OR for PPSV23 vaccination in the previous 5 years against pneumococcal CAP was 0.93 (95% CI: 0.35-2.50).

CONCLUSIONS

This study was unable to demonstrate the effectiveness of PPSV23 against all-cause and pneumococcal pneumonia after the introduction of childhood PCV13 in Japan. Nonetheless, additional studies are needed to validate these results.

Construction and protective efficacy of a novel Streptococcus pneumoniae fusion protein vaccine NanAT1-TufT1-PlyD4

During the past decades, with the implementation of pneumococcal polysaccharide vaccine (PPV) and pneumococcal conjugate vaccines (PCVs), a dramatic reduction in vaccine type diseases and transmissions has occurred. However, it is necessary to develop a less expensive, serotype-independent pneumococcal vaccine due to the emergence of nonvaccine-type pneumococcal diseases and the limited effect of vaccines on colonization. As next-generation vaccines, conserved proteins, such as neuraminidase A (NanA), elongation factor Tu (Tuf), and pneumolysin (Ply), are promising targets against pneumococcal infections. Here, we designed and constructed a novel fusion protein, NanAT1-TufT1-PlyD4, using the structural and functional domains of full-length NanA, Tuf and Ply proteins with suitable linkers based on bioinformatics analysis and molecular cloning technology. Then, we tested whether the protein protected against focal and lethal pneumococcal infections and examined its potential protective mechanisms. The fusion protein NanAT1-TufT1-PlyD4 consists of 627 amino acids, which exhibits a relatively high level of thermostability, high stability, solubility and a high antigenic index without allergenicity. The purified fusion protein was used to subcutaneously immunize C57BL/6 mice, and NanAT1-TufT1-PlyD4 induced a strong and significant humoral immune response. The anti-NanAT1-TufT1-PlyD4 specific IgG antibody assays increased after the first immunization and reached the highest value at the 35th day. The results from in vitro experiments showed that anti-NanAT1-TufT1-PlyD4 antisera could inhibit the adhesion of Streptococcus pneumoniae (S. pneumoniae) to A549 cells. In addition, immunization with NanAT1-TufT1-PlyD4 significantly reduced S. pneumoniae colonization in the lung and decreased the damage to the lung tissues induced by S. pneumoniae infection. After challenge with a lethal dose of serotype 3 (NC_WCSUH32403), a better protection effect was observed with NanAT1-TufT1-PlyD4-immunized mice than with the separate full-length proteins and the adjuvant control; the survival rate was 50%, which met the standard of the marketed vaccine. Moreover, we showed that the humoral immune response and the Th1, Th2 and Th17-cellular immune pathways are involved in the immune protection of NanAT1-TufT1-PlyD4 to the host. Collectively, our results support that the novel fusion protein NanAT1-TufT1-PlyD4 exhibits extensive immune stimulation and is effective against pneumococcal challenges, and these properties are partially attributed to humoral and cellular-mediated immune responses.