Upsurge of Conjugate Vaccine Serotype 4 Invasive Pneumococcal Disease Clusters Among Adults Experiencing Homelessness in California, Colorado, and New Mexico

Global distribution and characteristics of pneumococcal serotypes in adults

The introduction of pneumococcal conjugate vaccines (PCVs) into pediatric national immunization programs (NIP) has significantly reduced invasive pneumococcal diseases and pneumococcal pneumonia caused by PCV serotypes in adults due to herd immunity. However, diseases caused by PCV13 serotypes persist, mainly serotype 3, known for its severity. With the reduction in PCV13 serotypes, diseases caused by non-PCV13 serotypes increased. Residual and emerging serotypes vary regionally; serotype 8 in Europe and South Africa, and serotype 4 in the US and Canada. PCV20 and PCV21 were recently developed, which can prevent residual and emerging pneumococcal diseases where herd immunity is well-established. In countries that have not introduced PCV into pediatric NIP, the pneumococcal disease burden due to PCV serotypes is still marked. Given that serotype distribution varies by region and evolves over time, this review aimed to discuss serotype distribution and disease severity in adults across countries to support future pneumococcal vaccine strategies.

Increased Proportions of Invasive Pneumococcal Disease Cases Among Adults Experiencing Homelessness Sets the Stage for New Serotype 4 Capsular-Switch Recombinants

BACKGROUND

The Centers for Disease Control and Prevention's Active Bacterial Core surveillance (ABCs) identified increased serotype 4 invasive pneumococcal disease (IPD), particularly among adults experiencing homelessness (AEH).

METHODS

We quantified increased proportions of IPD cases in AEH during 2016-2022. Employing genomic-based characterization of IPD isolates, we identified serotype-switch variants. Recombinational analyses were used to identify the genetic donor and recipient strain that generated a serotype 4 progeny strain. We performed phylogenetic analyses of the serotype 4 progeny and of the serotype 12F genetic recipient to determine genetic distances.

RESULTS

We identified a cluster of 30 highly related (0-21 nucleotide differences) IPD isolates recovered during 2022-2023, corresponding to a serotype 4 capsular-switch variant. This strain arose through a multifragment recombination event between serotype 4/ST10172 and serotype 12F/ST220 parental strains. Twenty-five of the 30 cases occurred in Oregon. Of 29 cases with known residence status, 16 occurred in AEH. Variant emergence coincided with a 2.6-fold increase (57 to 148) of cases caused by the serotype 4/ST10172 donor lineage in 2022 compared to 2019 and its first appearance in Oregon. Most serotypes showed sequential increases of AEH IPD/all IPD ratios during 2016-2022 (eg, for all serotypes combined, 247/2198, 11.2% during 2022 compared to 405/5317, 7.6% for 2018-2019, P < .001). Serotypes 4 and 12F each caused more IPD than any other serotype in AEH during 2020-2022 (207 combined case isolates accounting for 38% of all IPD in AEH).

CONCLUSIONS

Expansion and increased transmission of serotypes 4 and 12F among adults potentially led to recent genesis of an impactful hybrid serotype-switch variant.

Distribution of pneumococcal serotypes causing invasive and non-invasive diseases in children in Mexico after introduction of PCV13 (2012-2023). Results from the GIVEBPVac group

BACKGROUND

The introduction of pneumococcal conjugate vaccines (PCVs) since 2000 has altered the epidemiology of invasive (IPD) and non-invasive pneumococcal diseases (NIPD). This study aims to analyze trends in pneumococcal serotype distribution among children in Mexico, focusing on the period following the introduction of PCV13, and assess the potential impact of future vaccines.

MATERIAL AND METHODS

Pneumococcal isolates were collected from hospitalized children in participating hospitals from January 2012 to December 2023. Serotype distribution was analyzed in children under <5 years and those aged ≥5 to 17.9 years. The average annual change (AAC) in serotype proportions was calculated, and trends were analyzed using the Cochran-Armitage test.

RESULTS

Serotype 19A was the most frequent PCV13 serotype, followed by serotypes 3 and 19F, in both age groups. Serotype 33F, included in PCV15 and PCV20, was absent in children aged ≥5-17.9 years. Among PCV20 serotypes, serotype 15B was the most common, and serotype 17F, covered by PCV24, showed a significant increase in the older age group (p = 0.037). No significant trends in the increase or decrease of individual serotypes were found, except for serotypes 17F and serotype 34, which increased in both age groups. A decrease in serotypes covered by PCV13 (excluding serotypes 3, 19A, and 19F) was observed in both age groups (p = 0.04, 0.002). A significant increase in non-PCV13 serotypes occurred in children aged ≥5-17.9 years (p = 0.023).

CONCLUSIONS

After a decade of the introduction of PCV13 in Mexico, 10 of the 13 vaccine serotypes have not been detected in the past six years. However, serotypes 3, 19A, and 19F persist at high frequencies as causes of IPD and NIPD in children. Ongoing robust surveillance is critical for identifying emerging pneumococcal serotypes, selecting appropriate vaccines for each country, and developing next-generation vaccine formulations.

Cost-Effectiveness and Public Health Impact of 24-Valent Pneumococcal Conjugate Vaccine Compared With the Recommended Pneumococcal Vaccines in Older Adults

INTRODUCTION

The potential impact of an in-development 24-valent pneumococcal conjugate vaccine compared with that of currently recommended vaccines in older adults is unclear. Similar to most currently available pneumococcal conjugate vaccines, 24-valent pneumococcal conjugate vaccine's formulation is based on childhood pneumococcal disease epidemiology. Decision analysis techniques were used to estimate 24-valent pneumococcal conjugate vaccine cost-effectiveness and public health effects in U.S. older adults.

METHODS

A Markov model compared 24-valent pneumococcal conjugate vaccine with currently recommended U.S. pneumococcal vaccination strategies in older adults (aged ≥65 years) and with no vaccination. Age-, race-, and chronic medical condition-specific pneumococcal illness risks and serotype-specific disease risks were obtained from Centers for Disease Control and Prevention data. Vaccine effectiveness was estimated using Delphi panel and clinical trial data. Vaccination and pneumococcal illness costs were from U.S.

DATABASES

Scenario analyses examined indirect effects of childhood pneumococcal vaccination on adult disease. Data were collected and analyses were performed in 2024.

RESULTS

The 24-valent pneumococcal conjugate vaccine prevented fewer pneumococcal disease cases and deaths than the recently recommended 21-valent pneumococcal conjugate vaccine, which is formulated on the basis of adult pneumococcal disease serotypes. In cost-effectiveness analyses, 21-valent pneumococcal conjugate vaccine was economically favorable compared with 24-valent pneumococcal conjugate vaccine and all other vaccination strategies, both without and with consideration of potential childhood vaccination indirect effects. These findings were robust and consistent with those in deterministic and probabilistic sensitivity analyses.

CONCLUSIONS

In older adults, 24-valent pneumococcal conjugate vaccine was clinically and economically unfavorable compared with 21-valent pneumococcal conjugate vaccine, which covers more adult disease-causing pneumococcal serotypes and is less susceptible to childhood vaccination indirect effects.

The Complex Landscape of Updated Pneumococcal Conjugate Vaccines

Pneumococcus is a major cause of serious infections, especially among vulnerable populations. While pneumococcal conjugate vaccines (PCVs) provide effective protection against disease caused by the included serotypes, a substantial burden of disease remains. Several new PCVs are under development or were recently recommended for use to counteract the remaining disease burden. This had led to complicated policy deliberations on their optimal use in different populations. We discuss how key factors should be considered in any policy decision: serotype coverage of a new PCV, prevalence of the untargeted remaining serotypes, strength of the immune response to the serotypes in a new PCV, potential for PCV evasion, PCV costs, and optimal simultaneous use of PCVs in children and adults. We also suggest the need for robust analyses of available surveillance data and continual monitoring of changes in the pneumococcal serotypes that are responsible for disease and colonization to help decision makers make optimal recommendations.

PNEUMOCOCCAL SEROTYPE DISTRIBUTION AND COVERAGE OF EXISTING AND PIPELINE PNEUMOCOCCAL VACCINES

Background

Streptococcus pneumoniae (pneumococcus) causes invasive pneumococcal disease (IPD) and non-invasive acute respiratory infections (ARIs). Three pneumococcal conjugate vaccines (PCVs) are recommended in the United States with additional products in clinical trials. We aimed to estimate 1) proportions of IPD cases and pneumococcal ARIs caused by serotypes targeted by existing and pipeline PCVs and 2) annual U.S. pneumococcal burdens potentially preventable by PCVs.

Methods

We estimated serotype distribution and proportions of non-invasive pneumococcal ARIs (AOM [children only], sinusitis, non-bacteremic pneumonia) and IPD attributable to serotypes targeted by each PCV using Markov chain Monte Carlo approaches incorporating data from studies of serotype distribution in ARIs and Active Bacterial Core Surveillance (ABCs) data. We then estimated annual numbers of outpatient-managed pneumococcal ARIs, non-bacteremic pneumococcal pneumonia hospitalizations, and IPD cases potentially preventable by PCVs in the United States by multiplying pneumococcal disease incidence rates by PCV-targeted proportions of disease and vaccine effectiveness estimates.

Results

In children, PCV15, PCV20, PCV24, PCV25, and PCV31 serotypes account for 16% (95% confidence interval: 15-17%), 31% (30-32%), 34% (32-35%), 43% (42-44%), and 68% (67-69%) of pneumococcal acute otitis media cases, respectively. In adults, PCV15, PCV20, PCV21, PCV24, PCV25, and PCV31 serotypes account for 43% (38-47%), 52% (47-57%), 69% (64-73%), 65% (61-70%), 62% (57-67%), and 87% (83-90%) of pneumococcal non-bacteremic pneumonia cases. For IPD, 42-85% of pediatric and 42-94% of adult cases were due to PCV-targeted serotypes. PCV-preventable burdens encompassed 270 thousand-3.3 million outpatient-managed ARIs, 2-17 thousand non-bacteremic pneumonia hospitalizations, and 3-14 thousand IPD cases in the United States annually.

Conclusions

Across pneumococcal conditions, coverage and preventable burdens were lowest for PCV15 and highest for PCV31, with PCV21 also targeting sizeable burdens of adult disease. Serotype distribution across syndromes may inform vaccine formulations and policy.

Prediction of post-PCV13 pneumococcal evolution using invasive disease data enhanced by inverse-invasiveness weighting

After introducing pneumococcal conjugate vaccines (PCVs), serotype replacement occurred in Streptococcus pneumoniae. Predicting which pneumococcal strains will become common in carriage after vaccination can enhance vaccine design, public health interventions, and understanding of pneumococcal evolution. Invasive pneumococcal isolates were collected during 1998-2018 by the Active Bacterial Core surveillance (ABCs). Carriage data from Massachusetts (MA) and Southwest United States were used to calculate weights. Using pre-vaccine data, serotype-specific inverse-invasiveness weights were defined as the ratio of the proportion of the serotype in carriage to the proportion in invasive data. Genomic data were processed under bioinformatic pipelines to define genetically similar sequence clusters (i.e., strains), and accessory genes (COGs) present in 5-95% of isolates. Weights were applied to adjust observed strain proportions and COG frequencies. The negative frequency-dependent selection (NFDS) model predicted strain proportions by calculating the post-vaccine strain composition in the weighted invasive disease population that would best match pre-vaccine COG frequencies. Inverse-invasiveness weighting increased the correlation of COG frequencies between invasive and carriage data in linear or logit scale for pre-vaccine, post-PCV7, and post-PCV13; and between different epochs in the invasive data. Weighting the invasive data significantly improved the NFDS model's accuracy in predicting strain proportions in the carriage population in the post-PCV13 epoch, with the adjusted R2 increasing from 0.254 before weighting to 0.545 after weighting. The weighting system adjusted invasive disease data to better represent the pneumococcal carriage population, allowing the NFDS mechanism to predict strain proportions in carriage in the post-PCV13 epoch. Our methods enrich the value of genomic sequences from invasive disease surveillance.IMPORTANCEStreptococcus pneumoniae, a common colonizer in the human nasopharynx, can cause invasive diseases including pneumonia, bacteremia, and meningitis mostly in children under 5 years or older adults. The PCV7 was introduced in 2000 in the United States within the pediatric population to prevent disease and reduce deaths, followed by PCV13 in 2010, PCV15 in 2022, and PCV20 in 2023. After the removal of vaccine serotypes, the prevalence of carriage remained stable as the vacated pediatric ecological niche was filled with certain non-vaccine serotypes. Predicting which pneumococcal clones, and which serotypes, will be most successful in colonization after vaccination can enhance vaccine design and public health interventions, while also improving our understanding of pneumococcal evolution. While carriage data, which are collected from the pneumococcal population that is competing to colonize and transmit, are most directly relevant to evolutionary studies, invasive disease data are often more plentiful. Previously, evolutionary models based on negative frequency-dependent selection (NFDS) on the accessory genome were shown to predict which non-vaccine strains and serotypes were most successful in colonization following the introduction of PCV7. Here, we show that an inverse-invasiveness weighting system applied to invasive disease surveillance data allows the NFDS model to predict strain proportions in the projected carriage population in the post-PCV13/pre-PCV15 and pre-PCV20 epoch. The significance of our research lies in using a sample of invasive disease surveillance data to extend the use of NFDS as an evolutionary mechanism to predict post-PCV13 population dynamics. This has shown that we can correct for biased sampling that arises from differences in virulence and can enrich the value of genomic data from disease surveillance and advance our understanding of how NFDS impacts carriage population dynamics after both PCV7 and PCV13 vaccination.

Surveillance of invasive pneumococcal disease in Spain exploring the impact of the COVID-19 pandemic (2019-2023)

OBJECTIVES

Dynamic trends of invasive pneumococcal disease (IPD) including the evolution of prevalent serotypes are very useful to evaluate the impact of current and future pneumococcal conjugate vaccines (PCVs) and the rise of non-vaccine serotypes. In this study, we include epidemiological patterns of S. pneumoniae before and after COVID-19 pandemic.

METHODS

We characterized all national IPD isolates from children and adults received at the Spanish Pneumococcal Reference Laboratory during 2019-2023.

RESULTS

In the first pandemic year 2020, we found a general reduction in IPD cases across all age groups, followed by a partial resurgence in children in 2021 but not in adults. By 2022, IPD cases in children had returned to pre-pandemic levels, and partially in adults. In 2023, IPD rates surpassed those of the last pre-pandemic year. Notably, the emergence of serotype 3 is of significant concern, becoming the leading cause of IPD in both pediatric and adult populations over the last two years (2022-2023). Increase of serotype 4 in young adults occurred in the last epidemiological years.

CONCLUSIONS

The COVID-19 pandemic led to a temporary decline in all IPD cases during 2020 attributable to non-pharmaceutical interventions followed by a subsequent rise. Employing PCVs with broader coverage and/or enhanced immunogenicity may be critical to mitigate the marked increase of IPD.

Invasive Pneumococcal Disease and Potential Impact of Pneumococcal Conjugate Vaccines Among Adults, Including Persons Experiencing Homelessness-Alaska, 2011-2020

BACKGROUND

Adults aged ≥65 years, adults with certain underlying medical conditions, and persons experiencing homelessness are at increased risk for invasive pneumococcal disease (IPD). Two new pneumococcal conjugate vaccines, 15-valent pneumococcal conjugate vaccine (PCV15) and 20-valent pneumococcal conjugate vaccine (PCV20), were recently approved for use in US adults. We describe the epidemiology of IPD among Alaska adults and estimate the proportion of IPD cases potentially preventable by new vaccines.

METHODS

We used statewide, laboratory-based surveillance data to calculate and compare IPD incidence rates and 95% confidence intervals (CIs) among Alaska adults aged ≥18 years during 2011-2020 and estimate the proportion of IPD cases that were caused by serotypes in PCV15 and PCV20.

RESULTS

During 2011-2020, 1164 IPD cases were reported among Alaska adults for an average annual incidence of 21.3 cases per 100 000 adults per year (95% CI, 20.1-22.5). Incidence increased significantly during the study period (P < .01). IPD incidence among Alaska Native adults was 4.7 times higher than among non-Alaska Native adults (95% CI, 4.2-5.2). Among adults experiencing homelessness in Anchorage, IPD incidence was 72 times higher than in the general adult population (95% CI, 59-89). Overall, 1032 (89%) Alaska adults with IPD had an indication for pneumococcal vaccine according to updated vaccination guidelines; 456 (39%) and 700 (60%) cases were caused by serotypes in PCV15 and PCV20, respectively.

CONCLUSIONS

Use of PCV15 and PCV20 could substantially reduce IPD among adults in Alaska, including Alaska Native adults and adults experiencing homelessness.

Pneumococcal serotypes missing prespecified efficacy threshold in immunogenicity trials: real-world evidence from national immunization programs

OBJECTIVES

The 13-valent (PCV13) and 10-valent (PCV10) pneumococcal conjugate vaccines missed non-inferiority for certain 7-valent (PCV7) serotypes in immunogenicity trials. This study examines the population-level IPD case trends for these serotypes.

METHODS

We identified six countries with national IPD surveillance data that introduced PCV13 (Canada, Germany, Israel, Italy, South Africa, and the United States) and three with PCV10 (Finland, Brazil, and the Netherlands). We extracted country-specific annual IPD case counts for PCV7 serotypes that missed non-inferiority and met non-inferiority (6B + 23F and PCV7 minus [6B + 23F] serotypes for PCV10 countries; 6B +9V + 23F, and PCV7 minus [6B +9V + 23F] serotypes for PCV13 countries) in clinical trials. Case count data for each country were plotted for observed serotype trends in different age groups (<5 and ≥5 years) for 8 years following PCV13/PCV10 introduction.

RESULTS

For all ages and countries, IPD cases due to PCV7 serotypes that missed non-inferiority either decreased or remained suppressed following PCV13/PCV10 introduction. Similar trends were found for PCV7 serotypes that met non-inferiority in those <5 years. Paradoxically, cases increased in those ≥5 years in Canada, Italy, and the US, primarily driven by increases in serotypes 4 and 19F disease.

CONCLUSIONS

Despite missing non-inferiority of serotypes in immunogenicity trials, higher-valent PCVs effectively suppressed these serotypes across all ages. Non-inferiority criteria from immunogenicity trials may not fully predict real-world disease impact after PCV implementation.

Prediction of post-PCV13 pneumococcal evolution using invasive disease data enhanced by inverse-invasiveness weighting

Background

After introduction of pneumococcal conjugate vaccines (PCVs), serotype replacement occurred in the population of Streptococcus pneumoniae. Predicting which pneumococcal clones and serotypes will become more common in carriage after vaccination can enhance vaccine design and public health interventions, while also improving our understanding of pneumococcal evolution. We sought to use invasive disease data to assess how well negative frequency-dependent selection (NFDS) models could explain pneumococcal carriage population evolution in the post-PCV13 epoch by weighting invasive data to approximate strain proportions in the carriage population.

Methods

Invasive pneumococcal isolates were collected and sequenced during 1998-2018 by the Active Bacterial Core surveillance (ABCs) from the Centers for Disease Control and Prevention (CDC). To predict the post-PCV13 population dynamics in the carriage population using a NFDS model, all genomic data were processed under a bioinformatic pipeline of assembly, annotation, and pangenome analysis to define genetically similar sequence clusters (i.e., strains) and a set of accessory genes present in 5% to 95% of the isolates. The NFDS model predicted the strain proportion by calculating the post-vaccine strain composition in the weighted invasive disease population that would best match pre-vaccine accessory gene frequencies. To overcome the biases of invasive disease data, serotype-specific inverse-invasiveness weights were defined as the ratio of the proportion of the serotype in the carriage data to the proportion in the invasive data, using data from 1998-2001 in the United States, before conjugate vaccine introduction. The weights were applied to adjust both the observed strain proportion and the accessory gene frequencies.

Results

Inverse-invasiveness weighting increased the correlation of accessory gene frequencies between invasive and carriage data with reduced residuals in linear or logit scale for pre-vaccine, post-PCV7, and post-PCV13. Similarly, weighting increased the correlation of accessory gene frequencies between different time periods in the invasive data. By weighting the invasive data, we were able to use the NFDS model to predict strain proportions in the carriage population in the post-PCV13 epoch, with the adjusted R-squared between predicted and observed strain proportions increasing from 0.176 to 0.544 after weighting.

Conclusions

The weighting system adjusted the invasive disease surveillance data to better represent the carriage population of S. pneumoniae. The NFDS mechanism predicted the strain proportions in the projected carriage population as estimated from the weighted invasive disease frequencies in the post-PCV13 epoch. Our methods enrich the value of genomic sequences from invasive disease surveillance, which is readily available, easy to collect, and of direct interest to public health.

Pneumococcal Vaccine for Adults Aged ≥19 Years: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023

This report compiles and summarizes all published recommendations from CDC’s Advisory Committee on Immunization Practices (ACIP) for use of pneumococcal vaccines in adults aged ≥19 years in the United States. This report also includes updated and new clinical guidance for implementation from CDC

Before 2021, ACIP recommended 23-valent pneumococcal polysaccharide vaccine (PPSV23) alone (up to 2 doses), or both a single dose of 13-valent pneumococcal conjugate vaccine (PCV13) in combination with 1–3 doses of PPSV23 in series (PCV13 followed by PPSV23), for use in U.S. adults depending on age and underlying risk for pneumococcal disease. In 2021, two new pneumococcal conjugate vaccines (PCVs), a 15-valent and a 20-valent PCV (PCV15 and PCV20), were licensed for use in U.S. adults aged ≥18 years by the Food and Drug Administration

ACIP recommendations specify the use of either PCV20 alone or PCV15 in series with PPSV23 for all adults aged ≥65 years and for adults aged 19–64 years with certain underlying medical conditions or other risk factors who have not received a PCV or whose vaccination history is unknown. In addition, ACIP recommends use of either a single dose of PCV20 or ≥1 dose of PPSV23 for adults who have started their pneumococcal vaccine series with PCV13 but have not received all recommended PPSV23 doses. Shared clinical decision-making is recommended regarding use of a supplemental PCV20 dose for adults aged ≥65 years who have completed their recommended vaccine series with both PCV13 and PPSV23

Updated and new clinical guidance for implementation from CDC includes the recommendation for use of PCV15 or PCV20 for adults who have received PPSV23 but have not received any PCV dose. The report also includes clinical guidance for adults who have received 7-valent PCV (PCV7) only and adults who are hematopoietic stem cell transplant recipients

Temporally Associated Invasive Pneumococcal Disease and SARS-CoV-2 Infection, Alaska, USA, 2020-2021

Streptococcus pneumoniae can co-infect persons who have viral respiratory tract infections. However, research on S. pneumoniae infections that are temporally associated with SARS-CoV-2 infections is limited. We described the epidemiology and clinical course of patients who had invasive pneumococcal disease (IPD) and temporally associated SARS-CoV-2 infections in Alaska, USA, during January 1, 2020-December 23, 2021. Of 271 patients who had laboratory-confirmed IPD, 55 (20%) had a positive SARS-CoV-2 test result. We observed no major differences in age, race, sex, or underlying medical conditions among IPD patients with and without SARS-CoV-2. However, a larger proportion of IPD patients with SARS-CoV-2 died (16%, n = 9) than for those with IPD alone (4%, n = 9) (p<0.01). IPD patients with SARS-CoV-2 were also more likely to be experiencing homelessness (adjusted OR 3.5; 95% CI 1.7-7.5). Our study highlights the risk for dual infection and ongoing benefits of pneumococcal and COVID-19 vaccination, especially among vulnerable populations.

Continued Increase of Erythromycin Nonsusceptibility and Clindamycin Nonsusceptibility Among Invasive Group A Streptococci Driven by Genomic Clusters, United States, 2018-2019

We analyzed 9630 invasive GAS surveillance isolates in the USA. From 2015-2017 to 2018-2019, significant increases in erythromycin-nonsusceptibility (18% vs 25%) and clindamycin-nonsusceptibility (17% vs 24%) occurred, driven by rapid expansions of genomic subclones. Prevention and control of clustered infections appear key to containing antimicrobial resistance.

Characterization of High Molecular Weight Pneumococcal Conjugate by SEC-MALS and AF4-MALS

Infections by Streptococcus pneumoniae can cause serious pneumococcal diseases and other medical complications among patients. Polysaccharide-based vaccines have been successfully developed as prophylactic agents against such deadly bacterial infections. In the 1980s, PNEUMOVAX® 23 were introduced as the first pneumococcal polysaccharide vaccines (PPSV). Later, pneumococcal polysaccharides were conjugated to a carrier protein to improve immune responses. Pneumococcal conjugate vaccines (PCV) such as PREVNAR® and VAXNEUVANCE™ have been developed. Of the more than 90 pneumococcal bacteria serotypes, serotype 1 (ST-1) and serotype 4 (ST-4) are the two main types that cause invasive pneumococcal diseases (IPD) that could lead to morbidity and mortality. Development of a novel multi-valent PCV against these serotypes requires extensive biophysical and biochemical characterizations of each monovalent conjugate (MVC) in the vaccine. To understand and characterize these high molecular weight (Mw) polysaccharide protein conjugates, we employed the multi-angle light scattering (MALS) technique coupled with size-exclusion chromatography (SEC) separation and asymmetrical flow field flow fractionation (AF4). MALS analysis of MVCs from the two orthogonal separation mechanisms helps shed light on the heterogeneity in conformation and aggregation states of each conjugate.

Invasive pneumococcal disease surveillance in Canada, 2020

Background

Invasive pneumococcal disease (IPD), which is caused by Streptococcus pneumoniae, has been a nationally notifiable disease in Canada since 2000. The use of conjugate vaccines has markedly decreased the incidence of IPD in Canada; however, the distribution of serotypes has shifted in favour of non-vaccine types. This report summarizes the demographics, serotypes and antimicrobial resistance of IPD infections in Canada in 2020.

Methods

The Public Health Agency of Canada's National Microbiology Laboratory (Winnipeg, Manitoba) collaborates with provincial and territorial public health laboratories to conduct national surveillance of IPD. A total of 2,108 IPD isolates were reported in 2020. Serotyping was performed by Quellung reaction and antimicrobial susceptibilities were determined in collaboration with the University of Manitoba/Canadian Antimicrobial Resistance Alliance. Population-based IPD incidence rates were obtained through the Canadian Notifiable Disease Surveillance System.

Results

Overall incidence of IPD in Canada decreased significantly from 11.5 (95% confidence interval [CI]: 10.1-13.1) to 6.0 (95% CI: 5.0-7.2), and from 10.0 (95% CI: 9.7-10.3) to 5.9 (95% CI: 5.7-6.2) cases per 100,000 from 2019 to 2020; in those younger than five years and those five years and older, respectively. The most common serotypes overall were 4 (11.2%, n=237), 3 (10.9%, n=229) and 8 (7.2%, n=151). From 2016 to 2020, serotypes with increasing trends (p<0.05) included 4 (6.4%-11.2%), 3 (9.5%-10.9%), 8 (5.2%-7.2%) and 12F (3.6%-5.7%). The overall prevalence of PCV13 serotypes increased over the same period (30.3%-34.9%, p<0.05). Antimicrobial resistance rates in 2020 included 23.0% clarithromycin and 9.9% penicillin (IV meningitis breakpoints). Multidrug-resistant IPD has significantly increased since 2016 (4.2%-9.5%, p<0.05).

Conclusion

Though the incidence of IPD decreased in 2020 in comparison to previous years across all age groups, disease due to PCV13 serotypes 3 and 4, as well as non-PCV13 serotypes such as 8 and 12F, increased in prevalence. Continued surveillance of IPD is imperative to monitor shifts in serotype distribution and antimicrobial resistance.

Invasive Pneumococcal Disease Clusters Disproportionally Impact Persons Experiencing Homelessness, Injecting Drug Users, and the Western United States

BACKGROUND

Invasive pneumococcal disease (IPD) isolates forming genomic clusters can reflect rapid disease transmission between vulnerable individuals.

METHODS

We performed whole genome sequencing of 2820 IPD isolates recovered during 2019 through Centers for Disease Control and Prevention's Active Bacterial Core surveillance to provide strain information (serotypes, resistance, genotypes), and 2778 of these genomes were analyzed to detect highly related genomic clusters.

RESULTS

Isolates from persons experiencing homelessness (PEH) were more often within genomic clusters than those from persons not experiencing homelessness (PNEH) (105/198 [53.0%] vs 592/2551 [23.2%]; P < .001). The 4 western sites accounted for 33.4% (929/2778) of isolates subjected to cluster analysis yet accounted for 48.7% (343/705) of clustering isolates (P < .001) and 75.8% (150/198) of isolates recovered from PEH (P < .001). Serotypes most frequent among PEH were (in rank order) 12F, 4, 3, 9N, 8, 20, and 22F, all of which were among the 10 serotypes exhibiting the highest proportions of clustering isolates among all cases. These serotypes accounted for 44.9% (1265/2820) of all IPD cases and are included within available vaccines.

CONCLUSIONS

We identified serotype-specific and geographic differences in IPD transmission. We show the vulnerability of PEH within different regions to rapidly spreading IPD transmission networks representing several pneumococcal serotypes included in available vaccines.

Impact of 13-Valent Pneumococcal Conjugate Vaccine on Invasive Pneumococcal Disease Among Adults With HIV-United States, 2008-2018

BACKGROUND

People with HIV (PWH) are at increased risk for invasive pneumococcal disease (IPD). Thirteen-valent pneumococcal conjugate vaccine (PCV13) was recommended for use in US children in 2010 and for PWH aged 19 years or older in 2012. We evaluated the population-level impact of PCV13 on IPD among PWH and non-PWH aged 19 years or older.

METHODS

We identified IPD cases from 2008 to 2018 through the Active Bacterial Core surveillance platform. We estimated IPD incidence using the National HIV Surveillance System and US Census Bureau data. We measured percent changes in IPD incidence from 2008 to 2009 to 2017-2018 by HIV status, age group, and vaccine serotype group, including serotypes in recently licensed 15-valent (PCV15) and 20-valent (PCV20) PCVs.

RESULTS

In 2008-2009 and 2017-2018, 8.4% (552/6548) and 8.0% (416/5169) of adult IPD cases were among PWH, respectively. Compared with non-PWH, a larger proportion of IPD cases among PWH were in adults aged 19-64 years (94.7%-97.4% vs. 56.0%-60.1%) and non-Hispanic Black people (62.5%-73.0% vs. 16.7%-19.2%). Overall and PCV13-type IPD incidence in PWH declined by 40.3% (95% confidence interval: -47.7 to -32.3) and 72.5% (95% confidence interval: -78.8 to -65.6), respectively. In 2017-2018, IPD incidence was 16.8 (overall) and 12.6 (PCV13 type) times higher in PWH compared with non-PWH; PCV13, PCV15/non-PCV13, and PCV20/non-PCV15 serotypes comprised 21.5%, 11.2%, and 16.5% of IPD in PWH, respectively.

CONCLUSIONS

Despite reductions post-PCV13 introduction, IPD incidence among PWH remained substantially higher than among non-PWH. Higher-valent PCVs provide opportunities to reduce remaining IPD burden in PWH.

International links between Streptococcus pneumoniae vaccine serotype 4 sequence type (ST) 801 in Northern European shipyard outbreaks of invasive pneumococcal disease

BACKGROUND

Pneumococcal disease outbreaks of vaccine preventable serotype 4 sequence type (ST)801 in shipyards have been reported in several countries. We aimed to use genomics to establish any international links between them.

METHODS

Sequence data from ST801-related outbreak isolates from Norway (n = 17), Finland (n = 11) and Northern Ireland (n = 2) were combined with invasive pneumococcal disease surveillance from the respective countries, and ST801-related genomes from an international collection (n = 41 of > 40,000), totalling 106 genomes. Raw data were mapped and recombination excluded before phylogenetic dating.

RESULTS

Outbreak isolates were relatively diverse, with up to 100 SNPs (single nucleotide polymorphisms) and a common ancestor estimated around the year 2000. However, 19 Norwegian and Finnish isolates were nearly indistinguishable (0-2 SNPs) with the common ancestor dated around 2017.

CONCLUSION

The total diversity of ST801 within the outbreaks could not be explained by recent transmission alone, suggesting that harsh environmental and associated living conditions reported in the shipyards may facilitate invasion of colonising pneumococci. However, near identical strains in the Norwegian and Finnish outbreaks does suggest that transmission between international shipyards also contributed to those outbreaks. This indicates the need for improved preventative measures in this working population including pneumococcal vaccination.

Pneumococcal infections and homelessness

Objective

To assess the prevalence of pneumococcal nasopharyngeal carriage, the role of potential risk factors, and the pneumococcal vaccination coverage among sheltered homeless people in Marseille, France.

Methods

During the winters 2015-2018, we enrolled 571 sheltered homeless males and 54 non-homeless controls. Streptococcus pneumoniae was directly searched from nasal/pharyngeal samples using real-time polymerase chain reaction.

Results

The homeless people were mostly migrants from African countries, with a mean age of 43 years. Pneumococcal vaccination coverage was low (3.1%). The overall pneumococcal carriage rate was 13.0% and was significantly higher in homeless people (15.3% in 2018) than in controls (3.7%), with p = 0.033. Among homeless people, being aged ≥ 65 years (1.97, 95% CI; 1.01-3.87), living in a specific shelter (OR = 1.80, 95% CI: 1.06-3.05), and having respiratory signs and symptoms at the time of enrolment (OR = 2.55, 95% CI: 1.54-4.21) were independently associated with pneumococcal carriage.

Conclusion

Pneumococcal nasopharyngeal carriage, which is a precursor for pneumococcal disease in at-risk individuals, is frequent among French homeless people. Studies conducted in other countries have also reported outbreaks of pneumococcal infections in homeless people. Pneumococcal vaccination should be systematically considered for sheltered homeless people in France, as is being done in Canada since 2008.

Is there a need for pneumococcal vaccination programs for the homeless to prevent invasive pneumococcal disease?

INTRODUCTION

Homeless are a vulnerable segment of society at risk for infections. Invasive pneumococcal disease (IPD) infections are increasingly identified in homeless as a major contributor of morbidity and mortality. Very few countries have recommended pneumococcal vaccination programs for the homeless.

AREAS COVERED

A literature review of IPD in the homeless from 1980 to 2020 in PubMed and Scopus using terms, 'homeless,' and 'homelessness,' and after 'chronic' or 'transitory' homeless was conducted. Gray literature from the CDC, WHO and major governmental agencies/organizations were included. Terms for IPD eligible for inclusion in the database search included 'pneumococcal disease,' 'invasive pneumococcal disease,' 'Streptococcus pneumoniae.' This included outbreaks of pneumococcal disease in the homeless, clinical characteristics associated with pneumococcal disease in the homeless, pneumococcal vaccines and vaccination recommendations for the homeless.

EXPERT OPINION

Homeless populations are at increased risk for IPD in comparison to the general population. This is due to clinical conditions experienced by the homeless including alcoholism and cigarette smoking. In addition, a collection of specific pneumococcal serotypes are associated with IPD in this group. Pneumococcal vaccine programs aimed at this population would likely decrease the incidence of IPD for this group and contribute to better overall health for the homeless.

Nonpneumococcal Strains Recently Recovered from Carriage Specimens and Expressing Capsular Serotypes Highly Related or Identical to Pneumococcal Serotypes 2, 4, 9A, 13, and 23A

The polysaccharide capsule is a key virulence factor of Streptococcus pneumoniae There are numerous epidemiologically important pneumococcal capsular serotypes, and recent findings have demonstrated that several of them are commonly found among nonpathogenic commensal species. Here, we describe 9 nonpneumococcal strains carrying close homologs of pneumococcal capsular biosynthetic (cps) loci that were discovered during recent pneumococcal carriage studies of adults in the United States and Kenya. Two distinct Streptococcus infantis strains cross-reactive with pneumococcal serotype 4 and carrying cps4-like capsular biosynthetic (cps) loci were recovered. Opsonophagocytic killing assays employing rabbit antisera raised against S. infantis US67cps4 revealed serotype 4-specific killing of both pneumococcal and nonpneumococcal strains. An S. infantis strain and two Streptococcus oralis strains, all carrying cps9A-like loci, were cross-reactive with pneumococcal serogroup 9 strains in immunodiffusion assays. Antiserum raised against S. infantis US64cps9A specifically promoted killing of serotype 9A and 9V pneumococcal strains as well as S. oralis serotype 9A strains. Serotype-specific PCR of oropharyngeal specimens from a recent adult carriage study in the United States indicated that such nonpneumococcal strains were much more common in this population than serotype 4 and serogroup 9 pneumococci. We also describe S. oralis and S. infantis strains expressing serotypes identical or highly related to serotypes 2, 13, and 23A. This study has expanded the known overlap of pneumococcal capsular serotypes with related commensal species. The frequent occurrence of nonpneumococcal strains in the upper respiratory tract that share vaccine and nonvaccine capsular serotypes with pneumococci could affect population immunity to circulating pneumococcal strains.IMPORTANCE The distributions and frequencies of individual pneumococcal capsular serotypes among nonpneumococcal strains in the upper respiratory tract are unknown and potentially affect pneumococcal serotype distributions among the population and immunity to circulating pneumococcal strains. Repeated demonstration that these nonpneumococcal strains expressing so-called pneumococcal serotypes are readily recovered from current carriage specimens is likely to be relevant to pneumococcal epidemiology, niche biology, and even to potential strategies of employing commensal live vaccines. Here, we describe multiple distinct nonpneumococcal counterparts for each of the pneumococcal conjugate vaccine (PCV) serotypes 4 and 9V. Additional data from contemporary commensal isolates expressing serotypes 2, 13, and 23A further demonstrate the ubiquity of such strains. Increased focus upon this serological overlap between S. pneumoniae and its close relatives may eventually prove that most, or possibly all, pneumococcal serotypes have counterparts expressed by the common upper respiratory tract commensal species Streptococcus mitis, Streptococcus oralis, and Streptococcus infantis.

Vaccine-preventable diseases other than tuberculosis, and homelessness: A scoping review of the published literature, 1980 to 2020

BACKGROUND

Homelessness may result in the breakdown of regular health services, including routine vaccination programmes. A scoping review was conducted to describe vaccine-preventable diseases (VPD) other than tuberculosis in people experiencing homelessness (PEH).

METHODS

We followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). We searched peer-reviewed literature published in English, French, Spanish or Portuguese reporting the outbreak of VPD or VPD prevalence in both infant and adult homeless populations published between 1980 and 2020, using PubMed/Medline, SciELO, Google Scholar, and Web of Science databases. Relevant information from the studies was charted in Microsoft Excel and results were summarised using a descriptive analytical method.

RESULTS

Eighty-one articles were included. A high prevalence of past hepatitis B virus (HBV) and hepatitis A virus (HAV) infections were observed through serosurveys, mostly in high income countries or high-middle income countries (USA, Canada, France, Iran or Brazil). Ten outbreaks of HAV infection were also reported, with lethality rates ranging from 0 to 4.8%. The studies identified numerous risk factors positively associated with HBV infection, including older age, homosexual or bisexual practice, injected drug use (IDU), and, with HAV infection including IDU, having sexual partner(s) with a history of unspecified hepatitis, insertive anal penetration, or originating from a country with a high prevalence of anti-HAV antibody. Eleven outbreaks of pneumococcal infection affecting PEH were reported in Canada and USA, with lethality rates from 0 to 15.6%. Six diphtheria outbreaks were reported. Vaccination status was rarely documented in these studies.

CONCLUSIONS

The literature suggests that homeless populations generally experience a high VPD burden suggesting the need for a national vaccination programme and planning for delivering vaccines in this population.

Identifying Missed Opportunities for Routine Vaccination among People Who Use Drugs

In the US, adult immunization coverage remains low, especially among vulnerable populations, as recent hepatitis A outbreaks have demonstrated. We studied the vaccination history variation among the US adults who use drugs by implementing a community-engaged research survey to identify reported immunization coverage, missed opportunities (MO), and places where immunizations might be delivered. Our analysis of a sample of 1127 participants recruited at community syringe exchanges in three cities identified higher overall vaccination receipt in Los Angeles compared to Atlanta or Las Vegas (e.g., HAV receipt 52.2% LA, 42.1% LV, 41.4% Atlanta). Overall, fewer participants reported having received HAV (45.9%), HBV (47.5%), or influenza (47.6%) vaccines than MMR (57.1%) or Td/Tdap (61.1%). Across sites, HAV receipt was higher for participants incarcerated ≥ 5 years (54.2% vs. 43.6% for those incarcerated < 5 years, 49.4% no incarceration history, p = 0.02). HBV receipt was higher among participants who were not intravenous drug users (56.1% vs. 46.0%, p = 0.03). Additionally, income >$20k predicted higher rates of MMR receipt (67.0% vs. 56.5%, p = 0.009), as did stable housing (62.8% vs. 54.3%, p = 0.01). To address the need to expand vaccine coverage among vulnerable adults, delivering vaccine at sites where persons who use drugs access services, or in correctional facilities, may be warranted.