Serotype-specific changes in invasive pneumococcal disease after pneumococcal conjugate vaccine introduction: a pooled analysis of multiple surveillance sites

Multicenter Hospital-Based Prospective Surveillance Study of Bacterial Agents Causing Meningitis and Seroprevalence of Different Serogroups of Neisseria meningitidis, Haemophilus influenzae Type b, and Streptococcus pneumoniae during 2015 to 2018 in Turkey

Acute bacterial meningitis (ABM) is one of the most common life-threatening infections in children. The incidence and prevalence of ABM vary both geographically and temporally; therefore, surveillance systems are necessary to determine the accurate burden of ABM. The Turkish Meningitis Surveillance Group has been performing a hospital-based meningitis surveillance study since 2005 across several regions in Turkey. Meningococcus was the major ABM-causing agent during the 2015-to-2018 period, during which MenB was the dominant serogroup.

The etiology of bacterial meningitis in Turkey changed after the implementation of conjugated vaccines against Streptococcus pneumoniae and Haemophilus influenzae type b (Hib) in the Turkish National Immunization Program (NIP). Administration of Hib vaccine and PCV-7 (7-valent pneumococcal conjugate vaccine) was implemented in NIP in 2006 and 2009, respectively. In 2011, PCV-7 was replaced with PCV-13. Meningococcal vaccines have not yet been included in Turkish NIP. This prospective study comprised 27 hospitals located in seven regions of Turkey and represented 45% of the population. Children aged between 1 month and 18 years who were hospitalized with suspected meningitis were included. Cerebrospinal fluid (CSF) samples were collected, and bacterial identification was made according to the multiplex PCR assay results. During the study period, 994 children were hospitalized for suspected meningitis, and Hib (n = 3, 2.4%), S. pneumoniae (n = 33, 26.4%), and Neisseria meningitidis (n = 89, 71%) were detected in 125 samples. The most common meningococcal serogroup was MenB. Serogroup W comprised 13.9% (n = 5) and 7.5% (n = 4) of the meningococci in 2015 to 2016 and 2017 to 2018, respectively. Serogroup C was not detected. There were four deaths in the study; one was a pneumococcus case, and the others were serogroup B meningococcus cases. The epidemiology of meningococcal diseases has varied over time in Turkey. Differing from the previous surveillance periods, MenB was the most common serogroup in the 2015-to-2018 period. Meningococcal epidemiology is so dynamic that, for vaccination policies, close monitoring is crucial.

IMPORTANCE Acute bacterial meningitis (ABM) is one of the most common life-threatening infections in children. The incidence and prevalence of ABM vary both geographically and temporally; therefore, surveillance systems are necessary to determine the accurate burden of ABM. The Turkish Meningitis Surveillance Group has been performing a hospital-based meningitis surveillance study since 2005 across several regions in Turkey. Meningococcus was the major ABM-causing agent during the 2015-to-2018 period, during which MenB was the dominant serogroup.

Capturing multiple-type interactions into practical predictors of type replacement following human papillomavirus vaccination

Current HPV vaccines target a subset of the oncogenic human papillomavirus (HPV) types. If HPV types compete during infection, vaccination may trigger replacement by the non-targeted types. Existing approaches to assess the risk of type replacement have focused on detecting competitive interactions between pairs of vaccine and non-vaccine types. However, methods to translate any inferred pairwise interactions into predictors of replacement have been lacking. In this paper, we develop practical predictors of type replacement in a multi-type setting, readily estimable from pre-vaccination longitudinal or cross-sectional prevalence data. The predictors we propose for replacement by individual non-targeted types take the form of weighted cross-hazard ratios of acquisition versus clearance, or aggregate odds ratios of coinfection with the vaccine types. We elucidate how the hazard-based predictors incorporate potentially heterogeneous direct and indirect type interactions by appropriately weighting type-specific hazards and show when they are equivalent to the odds-based predictors. Additionally, pooling type-specific predictors proves to be useful for predicting increase in the overall non-vaccine-type prevalence. Using simulations, we demonstrate good performance of the predictors under different interaction structures. We discuss potential applications and limitations of the proposed methodology in predicting type replacement, as compared to existing approaches. This article is part of the theme issue 'Silent cancer agents: multi-disciplinary modelling of human DNA oncoviruses'.

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.

Designing ecologically optimized pneumococcal vaccines using population genomics

Streptococcus pneumoniae (the pneumococcus) is a common nasopharyngeal commensal that can cause invasive pneumococcal disease (IPD). Each component of current protein-polysaccharide conjugate vaccines (PCVs) generally induces immunity specific to one of the approximately 100 pneumococcal serotypes, and typically eliminates it from carriage and IPD through herd immunity. Overall carriage rates remain stable owing to replacement by non-PCV serotypes. Consequently, the net change in IPD incidence is determined by the relative invasiveness of the pre- and post-PCV-carried pneumococcal populations. In the present study, we identified PCVs expected to minimize the post-vaccine IPD burden by applying Bayesian optimization to an ecological model of serotype replacement that integrated epidemiological and genomic data. We compared optimal formulations for reducing infant-only or population-wide IPD, and identified potential benefits to including non-conserved pneumococcal carrier proteins. Vaccines were also devised to minimize IPD resistant to antibiotic treatment, despite the ecological model assuming that resistance levels in the carried population would be preserved. We found that expanding infant-administered PCV valency is likely to result in diminishing returns, and that complementary pairs of infant- and adult-administered vaccines could be a superior strategy. PCV performance was highly dependent on the circulating pneumococcal population, further highlighting the advantages of a diversity of anti-pneumococcal vaccination strategies.

Clinical Relevance and Molecular Pathogenesis of the Emerging Serotypes 22F and 33F of Streptococcus pneumoniae in Spain

Streptococcus pneumoniae is the main bacterial cause of respiratory infections in children and the elderly worldwide. Serotype replacement is a frequent phenomenon after the introduction of conjugated vaccines, with emerging serotypes 22F and 33F as frequent non-PCV13 serotypes in children and adults in North America and other countries. Characterization of mechanisms involved in evasion of the host immune response by these serotypes is of great importance in public health because they are included in the future conjugated vaccines PCV15 and PCV20. One of the main strategies of S. pneumoniae to persistently colonize and causes infection is biofilm formation. In this study, we have evaluated the influence of capsule polysaccharide in biofilm formation and immune evasion by using clinical isolates from different sources and isogenic strains with capsules from prevalent serotypes. Since the introduction of PCV13 in Spain in the year 2010, isolates of serotypes 22F and 33F are rising among risk populations. The predominant circulating genotypes are ST433^22F and ST717^33F, being CC433 in 22F and CC717 in 33F the main clonal complexes in Spain. The use of clinical isolates of different origin, demonstrated that pediatric isolates of serotypes 22F and 33F formed better biofilms than adult isolates and this was statistically significant. This phenotype was greater in clinical isolates from blood origin compared to those from cerebrospinal fluid, pleural fluid and otitis. Opsonophagocytosis assays showed that serotype 22F and 33F were recognized by the PSGL-1 receptor on leukocytes, although serotype 22F, was more resistant than serotype 33F to phagocytosis killing and more lethal in a mouse sepsis model. Overall, the emergence of additional PCV15 serotypes, especially 22F, could be associated to an enhanced ability to divert the host immune response that markedly increased in a biofilm state. Our findings demonstrate that pediatric isolates of 22F and 33F, that form better biofilm than isolates from adults, could have an advantage to colonize the nasopharynx of children and therefore, be important in carriage and subsequent dissemination to the elderly. The increased ability of serotype 22F to avoid the host immune response, might explain the emergence of this serotype in the last years.

Serotype and clonal distribution dynamics of invasive pneumococcal strains after PCV13 introduction (2011-2016): Surveillance data from 23 sites in Catalonia, Spain

Background

The objective of this study is to describe incidence and shifts of serotype and clonal distribution of invasive Streptococcus pneumoniae strains in four different age groups (<5 years, 5–17 years, 18–64 years and >65 years) during a period of intermediate PCV13 vaccination coverage (2011–2016) in Catalonia, Spain.

Methods

We included all pneumococcal strains systematically sent to the Catalan support laboratory for molecular surveillance of invasive pneumococcal disease (IPD) located at Hospital Sant Joan de Deu, Barcelona. Two study periods were considered: 2011–13, early PCV13 vaccination period (EVP) and 2014–2016, late vaccination period (LVP).

Results

A total of 2142 strains were included in the study. Five years after intermediate introduction of PCV13 in our population, a significant decrease of overall incidence of IPD in children <5 years was observed (incidence rate ratio 0.5, 95% confidence interval 0.4–0.8). However, in seniors older than 65 years, a significant increase of overall incidence of IPD was observed (IRR 1.4, 95% CI 1.1–1.7). The contribution of PCV13 vaccine serotypes to IPD declined significantly in all age groups: from 59% to 38.1% in <5 years; 82.7% to 59% in 5–17 years, 47.8% to 34.1% in 18–64 years and 48.2% to 37% in >65 years. Results found when comparing both periods were consistent with IRRs observed year by year. In children <5 years, the three major serotypes detected were 1, 24F and 19A in EVP vs 24F, 14 and 10A in LVP. Among patients 5–17 years the first three serotypes were 1, 12F and 14 both in EVP and LVP. Among adults 18–64, the three major serotypes detected were 1, 12F and 8 vs 8, 12F and 3, respectively. Finally, in patients >65 years the most frequently isolated serotypes were 3, 19A and 7F vs 3, 14 and 12F, respectively. Regarding clonal complexes (CCs) expressing mainly PCV13 serotypes, significant decreases of the proportions of CC306, CC191 and CC320 were observed, while CC156 showed a significant increase. As for CCs expressing mostly non-PCV13 serotypes, significant increases in ST989, CC53 and CC404 were showed.

Conclusions

Despite low vaccine coverage in our setting a significant decrease of incidence of IPD was observed in children younger than 5 years. The modest indirect protection against vaccine serotypes causing IPD in elderly indicate the need for the inclusion of more serotypes in future high-valent PCV and vaccinating old adults should be considered.

Conjugate vaccines dramatically reshaped the epidemiology of bacterial meningitis in a well-defined child population

AIM

We explored the impact of vaccination on bacterial meningitis in a well-defined population of children on the island of Crete, Greece, over a 27-y period.

METHODS

This was a retrospective observational study of all mandatory notifications of bacterial meningitis in patients aged 1 mo-14 y from 1991 to 2017.

RESULTS

There were 245 patients with proven (n = 227) or suspected (n = 18) bacterial meningitis, and eight deaths were recorded, giving a case fatality rate of 3.3%. The mean annual incidence rate (IR) per 100 000 children was 4.9 for Neisseria meningitidis, 2.2 for Streptococcus pneumoniae and 0.4 for Haemophilus influenzae type b (Hib). Cases of meningitis C dropped significantly after the conjugate meningitis C vaccine was licensed for routine vaccination in Greece in 2000 (IR of 1.5 vs 0.3, P < 0.028) while the Streptococcus pneumoniae cases showed a threefold decrease after the PCV13 vaccine was licensed in Greece in 2009 (IR 2.7 vs 1.0, P < 0.03). Vaccination had already eliminated Hib in Greece in the 1990s.

CONCLUSION

Bacterial meningitis cases decreased in children following the introduction of the meningitis C and PCV13 vaccines in Greece. Hib had already disappeared and significant reductions in meningitis C and Streptococcus pneumoniae were observed.

Commentary: Why Has Uptake of Pneumococcal Vaccines for Children Been So Slow? The Perils of Undervaluation

Pediatric pneumococcal disease exacts a substantial burden on global health, much of which is vaccine-preventable. Despite this considerable burden and the demonstrably high efficacy of pneumococcal conjugate vaccines (PCVs), the overall level of PCV uptake remains concerningly low, especially compared with that of other childhood-recommended vaccines, such as tuberculosis and polio. A broad set of plausible explanations exists for this low uptake, including logistical challenges, psychosocial factors and affordability. One additional and systematic cause of low uptake, which is the focus of our discussion, is economists' and policymakers' tendency to undervalue vaccination in general by adopting a narrow health sector perspective when performing economic evaluations of vaccines. We present an alternative, societal framework for economic evaluations that encompasses a broader set of socioeconomic benefits in addition to health benefits. Quantifying a more comprehensive taxonomy of PCV's benefits will help to address potential undervaluation and may be sufficient not only to justify recommendation and reimbursement but also to stimulate efforts and investment toward closing coverage gaps.

The long search for a serotype independent pneumococcal vaccine

Introduction: Serotype replacement - a consequence of polysaccharide vaccine use - will continue to drive the inclusion of new serotypes on conjugate vaccines, increasing production complexity and costs, and making an already expensive vaccine less accessible to developing countries, where prevalence is higher and resources available for health systems, scarcer. Serotype-independent formulations are a promising option, but so far they have not been successful in reducing colonization/transmission.Areas covered: Protein-based and whole-cell vaccine candidates studied in the past 30 years. Challenges for serotype-independent vaccine development and alternative approaches.Expert opinion: Clinical trials performed so far demonstrated the importance to establish more reliable animal models and better correlates of protection. Defining appropriate endpoints for clinical trials of serotype-independent vaccine candidates has been a challenge. Inhibition of colonization has been evaluated, but concern on the extent of bacterial elimination is still a matter of debate. Challenges on establishing representative sites for clinical trials, sample sizes and appropriate age groups are discussed. On a whole, although many challenges will have to be overcome, establishing protein-based antigens as serotype-independent vaccines is still the best alternative against the huge burden of pneumococcal diseases in the world.

The Use of Test-negative Controls to Monitor Vaccine Effectiveness: A Systematic Review of Methodology

BACKGROUND

The test-negative design is an increasingly popular approach for estimating vaccine effectiveness (VE) due to its efficiency. This review aims to examine published test-negative design studies of VE and to explore similarities and differences in methodological choices for different diseases and vaccines.

METHODS

We conducted a systematic search on PubMed, Web of Science, and Medline, for studies reporting the effectiveness of any vaccines using a test-negative design. We screened titles and abstracts and reviewed full texts to identify relevant articles. We created a standardized form for each included article to extract information on the pathogen of interest, vaccine(s) being evaluated, study setting, clinical case definition, choices of cases and controls, and statistical approaches used to estimate VE.

RESULTS

We identified a total of 348 articles, including studies on VE against influenza virus (n = 253), rotavirus (n = 48), pneumococcus (n = 24), and nine other pathogens. Clinical case definitions used to enroll patients were similar by pathogens of interest but the sets of symptoms that defined them varied substantially. Controls could be those testing negative for the pathogen of interest, those testing positive for nonvaccine type of the pathogen of interest, or a subset of those testing positive for alternative pathogens. Most studies controlled for age, calendar time, and comorbidities.

CONCLUSIONS

Our review highlights similarities and differences in the application of the test-negative design that deserve further examination. If vaccination reduces disease severity in breakthrough infections, particular care must be taken in interpreting vaccine effectiveness estimates from test-negative design studies.

Invasive pneumococcal disease among hospitalized children in Brazil before and after the introduction of a pneumococcal conjugate vaccine

BACKGROUND

Most of the available data on invasive pneumococcal disease in Latin America are derived from laboratory-based surveillance systems. There is a lack of epidemiological data on the disease severity and mortality from hospitalized patients with pneumococcal infection.

METHODS

In this hospital-based retrospective historical series of hospitalized children with laboratory-confirmed IPD, we evaluated changes in disease episodes, in-hospital fatality rates, and need for intensive care unit admission after the inclusion of PCV10 in the Brazilian vaccination schedule. Invasive pneumococcal strains isolated by culture were serotyped. Changes over time were assessed, and pre-vaccination (2005-2009) to post-vaccination (2011-2015) disease rates and serotypes were compared.

RESULTS

260 patients with IPD and positive pneumococcal isolates were identified (198 during the pre-PCV10 period). When comparing both periods, hospitalizations were reduced from 20 cases to 5 cases per 10,000 pediatric admissions (p < 0.0001). Likewise, fatalities reduced from 6.6 to 2.0 cases per 10,000 pediatric admissions (p < 0.0001). Pneumonia was the most frequent clinical diagnosis (58%) - of which 49.6% had pleural effusion - followed by meningitis (22%) and bacteremia (15.9%). Overall 30% of cases were sent to ICU, with no percentual changes after PCV10. Additional PCV13 serotypes increased from 7% before vaccine introduction to 21% after PCV10 use. Similarly, serotypes not included in PCV13 increased from 11% to 29%.

CONCLUSIONS

There was a significant reduction in the hospitalizations rates, ICU admissions, and fatalities due to IPD after PCV10 introduction in Brazil. Cases due to PCV10 serotypes were reduced, while infections rates caused by non-PCV10 serotypes increased.

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.

Serotype distribution and antimicrobial resistance of Streptococcus pneumoniae causing invasive diseases in China: a meta-analysis

Background

To summarize information about invasive pneumococcal disease (IPD) among children in mainland China.

Methods

Sixteen eligible studies were included in this systematic review and the random effect model was used to estimate the pool prevalence of IPD.

Results

The most predominant serotypes circulating in children were 19F (27.7, 95% confidence interval (95% CI): 17.7–37.6%), 19A (21.2%, 16.4–26.1%), 14 (16.5%, 12.8–20.1%), 6B (8.6%, 5.2–10.8%) and 23F (7.3%, 5.2–9.5%). The serotype coverage of the available pneumococcal conjugate vaccines PCV7, PCV10, and PCV13 was 60.8% (52.5–69.4%), 65.1% (57.7–72.4%), and 90.0% (87.1–92.8%), respectively. The pooled antibiotic resistance rates of Streptococcus pneumoniae revealed a resistance to penicillin prevalence rate of 32.0% (12.1–51.9%). Approximately 94.4% (90.7–98.1%) and 92.3% (87.4–97.3%) of isolates were resistant to erythromycin and clindamycin. eBURST analysis revealed great diversity among isolates, with 102 sequence types (STs) for 365 isolates. The major predominant clonal complexes (CCs) were CC271 (43.6%, 159/365), CC876 (13.4%, 49/365), CC81 (5.2%, 19/365), and CC90 (4.1%, 15/365). Long-term and regional surveillance of S. pneumoniae is necessary.

Conclusions

Based on our pooled results showing that PCV13 coverage of the reported serotypes was 90% and that most serotypes contributed to the distribution of antibiotic-resistant isolates, implementation of PCV13 into the Chinese Expanded Program on Immunizations (EPI) would achieve health benefits in Chinese children.

Serotype evolution in Western Europe: perspectives on invasive pneumococcal diseases (IPD)

Introduction: Epidemiologic trends for IPD have evolved with the introduction of pneumococcal conjugate vaccines into childhood immunization programs. We document the ongoing impact of PCV programs in 15 Western European countries.Areas covered: Data were collected from relevant published observational studies and national surveillance websites from January 2010 through January 2018. In countries using PCV13, the proportion of IPD due to PCV13 serotypes declined significantly (from 60-78% to 8-26%) in children <5 years of age within 5-8 years following vaccine introduction. In countries using PCV10, a marked decrease in PCV10-serotype IPD was reported; however, the proportion of IPD due to PCV13 serotypes remained high at 58-64%, predominantly due to serotypes 19A and 3.Expert opinion: The prevalence of vaccine-type IPD in adults remained high; emerging non-vaccine serotypes such as 8, 12F, 22F, 33F, and 15B/C should be a focus of future vaccine development.

Effectiveness of 7- and 13-Valent Pneumococcal Conjugate Vaccines in a Schedule Without a Booster Dose: A 10-Year Observational Study

Background

Unique among high-income countries, Australia has used a 3 + 0 schedule (3 primary doses, no booster) for infant pneumococcal conjugate vaccine (PCV) since January 2005, initially 7 valent (PCV7) then 13 valent (PCV13) from July 2011. We measured vaccine effectiveness (VE) of both PCVs against invasive pneumococcal disease (IPD) using 2 methods.

Methods

Cases were IPD notifications to the national surveillance system of children eligible for respective PCVs. For case-control method, up to 10 age-matched controls were derived from the Australian Childhood Immunisation Register. For indirect cohort method, controls were IPD cases due to serotypes not in PCVs. VE was calculated as (1 - odds ratio [OR]) × 100 by logistic regression. VE waning was estimated as odds of vaccine type (VT) IPD in consecutive 12-month periods post-dose 3.

Results

Between 2005 and 2014, there were 1209 and 308 IPD cases in PCV7-eligible and PCV13-eligible cohorts, respectively. Both methods gave comparable VE estimates. In infants, VE for 3 doses against VT IPD was 92.9% (95% confidence interval [CI], 27.7% to 99.3%) for PCV7 and 86.5% (95% CI, 11.7% to 97.9%) for PCV13. From 12 months post-dose 3, the odds of VT IPD by 24-36 months increased significantly for PCV7 (5.6, 95% CI, 1.2-25.4) and PCV13 (5.9, 95% CI, 1.0-35.2).

Conclusions

For both PCVs in a 3 + 0 schedule, despite similar VE, progressive increase in breakthrough cases only occurred post-PCV13. This supports the importance of a booster dose of PCV13 in the second year of life to maintain protection.

Pneumococcal Vaccines

Streptococcus pneumoniae is a Gram-Positive pathogen that is a major causative agent of pneumonia, otitis media, sepsis and meningitis across the world. The World Health Organization estimates that globally over 500,000 children are killed each year by this pathogen. Vaccines offer the best protection against S. pneumoniae infections. The current polysaccharide conjugate vaccines have been very effective in reducing rates of invasive pneumococcal disease caused by vaccine type strains. However, the effectiveness of these vaccines have been somewhat diminished by the increasing numbers of cases of invasive disease caused by non-vaccine type strains, a phenomenon known as serotype replacement. Since, there are currently at least 98 known serotypes of S. pneumoniae, it may become cumbersome and expensive to add many additional serotypes to the current 13-valent vaccine, to circumvent the effect of serotype replacement. Hence, alternative serotype independent strategies, such as vaccination with highly cross-reactive pneumococcal protein antigens, should continue to be investigated to address this problem. This chapter provides a comprehensive discussion of pneumococcal vaccines past and present, protein antigens that are currently under investigation as vaccine candidates, and other alternatives, such as the pneumococcal whole cell vaccine, that may be successful in reducing current rates of disease caused by S. pneumoniae.

Pneumococcal conjugate vaccine use during humanitarian crises

Streptococcus pneumoniae is a common human commensal that causes a sizeable part of the overall childhood mortality in low income settings. Populations affected by humanitarian crises are at especially high risk, because a multitude of risk factors that are enhanced during crises increase pneumococcal transmission and disease severity. Pneumococcal conjugate vaccines (PCVs) provide effective protection and have been introduced into the majority of routine childhood immunisation programmes globally, though several barriers have hitherto limited their uptake during humanitarian crises. When PCV coverage cannot be sustained during crises or when PCV has not been part of routine programmes, mass vaccination campaigns offer a quick acting and programmatically feasible bridging solution until services can be restored. However, we currently face a paucity of evidence on which to base the structure of such campaigns. We believe that, now that PCV can be procured at a substantially reduced price through the Humanitarian Mechanism, this lack of information is a remaining hurdle to PCV use in humanitarian crises. Considering the difficulties in conducting research in crises, we propose an evidence generation pathway consisting of primary data collection in combination with mathematical modelling followed by quasi-experimental evaluation of a PCV intervention, which can inform on optimal vaccination strategies that consider age targeting, dosing regimens and impact duration.

Associations between ethnicity, social contact, and pneumococcal carriage three years post-PCV10 in Fiji

BACKGROUND

Pneumococcal carriage is a prerequisite for pneumococcal disease. Little is known about whether social contact frequency and intensity are associated with pneumococcal carriage. In Fiji, indigenous iTaukei have higher prevalence of pneumococcal carriage compared with Fijians of Indian Descent (FID). We hypothesised that contact differences may contribute to ethnic differences in pneumococcal carriage prevalence and density.

METHODS

In 2015, young infants (5-8 weeks), toddlers (12-23 months), children (2-6 years), and caregivers from Suva and surrounding areas, participated in a cross-sectional survey (n = 2014), three years post pneumococcal conjugate vaccine introduction. Demographic and contact data, and nasopharyngeal swabs were collected. Pneumococci were detected, and quantified using quantitative real-time PCR, with molecular serotyping by microarray. Associations between ethnicity, contact, and pneumococcal carriage and density were estimated using multivariable generalised estimating equation regression models.

RESULTS

iTaukei participants had larger household sizes, higher pneumococcal carriage rates, more contacts, and more frequent contacts of longer duration, compared with FID. The odds of vaccine-type carriage increased by 28% (95% CI 8-53%) P < 0.01 in association with physical contact with 7-14 year old children. iTaukei ethnicity was associated with vaccine-type carriage (aOR) 1.73; 95% CI 1.06-2.82, P = 0.03) and non-vaccine type carriage (aOR 5.98; 95% CI 4.47-8.00, P < 0.01). Ethnicity and contact were not associated with pneumococcal density.

CONCLUSIONS

iTaukei had greater frequency and intensity of contact compared with FID. Physical contact was associated with pneumococcal carriage. Observed differences in pneumococcal nasopharyngeal carriage prevalence between iTaukei and FID were not explained by differences in social contact patterns by ethnicity.

Meeting report: Global vaccine and immunization research forum, 2018

Every two years, the Global Vaccine and Immunization Research Forum takes stock of global research in vaccines and immunization. As in prior years, the 2018 meeting addressed vaccine discovery, development, decision-making, and deployment. This time, however, it also featured two overarching themes: "Innovating for Equity" and "End-to-End Integration." Significant advances have been made in the last two years, but participants noted that some important goals of the Global Vaccine Action Plan are not being met and called urgently for innovation in improving access to vaccines. Two factors were highlighted as crucial to improving coverage: a focus on equity and sustainability throughout the immunization ecosystem, and an enabling political environment that prioritizes health and immunization.

Pneumococcal Community-Acquired Pneumonia Detected by Serotype-Specific Urinary Antigen Detection Assays

Background

Streptococcus pneumoniae is considered the leading bacterial cause of pneumonia in adults. Yet, it was not commonly detected by traditional culture-based and conventional urinary testing in a recent multicenter etiology study of adults hospitalized with community-acquired pneumonia (CAP). We used novel serotype-specific urinary antigen detection (SSUAD) assays to determine whether pneumococcal cases were missed by traditional testing.

Methods

We studied adult patients hospitalized with CAP at 5 hospitals in Chicago and Nashville (2010-2012) and enrolled in the Etiology of Pneumonia in the Community (EPIC) study. Traditional diagnostic testing included blood and sputum cultures and conventional urine antigen detection (ie, BinaxNOW). We applied SSUAD assays that target serotypes included in the 13-valent pneumococcal conjugate vaccine (PCV13) to stored residual urine specimens.

Results

Among 1736 patients with SSUAD and ≥1 traditional pneumococcal test performed, we identified 169 (9.7%) cases of pneumococcal CAP. Traditional tests identified 93 (5.4%) and SSUAD identified 76 (4.4%) additional cases. Among 14 PCV13-serotype cases identified by culture, SSUAD correctly identified the same serotype in all of them. Cases identified by SSUAD vs traditional tests were similar in most demographic and clinical characteristics, although disease severity and procalcitonin concentration were highest among those with positive blood cultures. The proportion of pneumonia cases caused by serotypes exclusively covered by PCV13 was not significantly different between the first and second July-June study periods (6.4% vs 4.0%).

Conclusions

Although restricted to the detection of only 13 serotypes, SSUAD testing substantially increased the detection of pneumococcal pneumonia among adults hospitalized with CAP.

Prevalence of Various Vaccine Candidate Proteins in Clinical Isolates of Streptococcus pneumoniae: Characterization of the Novel Pht Fusion Proteins PhtA/B and PhtA/D

Pneumococcal proteins unrelated to serotypes are considered to be candidates of antigens in next-generation vaccines. In the present study, the prevalence of vaccine candidate protein genes, along with serotypes and antimicrobial resistance determinants, was investigated in a total of 57 isolates obtained from a tertiary care hospital in Japan. All of the pediatric isolates and 76.6% of the adult isolates did not belong to PCV13 (a 13-valent pneumococcal conjugate vaccine) serotypes, and 70.2% of all isolates showed multidrug resistance. All of the isolates had ply, pavA, nanA, and nanB, and high prevalence was noted for the pspA and pspC genes (96.5% and 78.9%, respectively). Detection rates for the pneumococcal histidine triad protein (Pht) genes phtA, phtB, phtD, and phtE were 49.1%, 26.3%, 61.4%, and 100%, respectively. Two fusion-type genes, phtA/B and phtA/D, were identified, with a prevalence of 36.9% and 14.0%, respectively. These fusion types showed 78.1–90.0% nucleotide sequence identity with phtA, phtB, and phtD. The most prevalent pht profile was phtA + phtD + phtE (26.3%), followed by phtA/B + phtE (19.3%) and phtA/B + phtD + phtE (17.5%), while pht profiles including phtD and/or phtA/phtD were found in 71.9% of isolates. The present study revealed the presence of two fusion types of Pht and their unexpectedly high prevalence. These fusion types, as well as PhtA and PhtB, contained sequences similar to the B cell epitopes that have been previously reported for PhtD.

Community-acquired acute bacterial meningitis in adults: a clinical update

BACKGROUND

Acute bacterial meningitis (ABM) in adults is associated with a mortality that may exceed 30%. Immunization programs have reduced the global burden; in the UK, declining incidence but persistently high mortality and morbidity mean that clinicians must remain vigilant.

SOURCES OF DATA

A systematic electronic literature search of PubMed was performed to identify all ABM literature published within the past 5 years.

AREAS OF AGREEMENT AND CONTROVERSY

Clinical features cannot reliably distinguish between ABM and other important infectious and non-infectious aetiologies. Prompt investigation and empirical treatment are imperative. Lumbar puncture (LP) and cerebrospinal fluid microscopy, biochemistry and culture remain the mainstay of diagnosis, but molecular techniques are increasingly useful. The 2016 UK joint specialist societies' guideline provides expert recommendations for the management of ABM, yet published data suggest clinical care delivered in the UK is frequently not adherent. Anxiety regarding risk of cerebral herniation following LP, unnecessary neuroimaging, underutilization of molecular diagnostics and suboptimal uptake of adjunctive corticosteroids compromise management.

GROWING POINTS

There is increasing recognition that current antibiotic regimens and adjunctive therapies alone are insufficient to reduce the mortality and morbidity associated with ABM.

AREAS TIMELY FOR DEVELOPING RESEARCH

Research should be focused on optimization of vaccines (e.g. pneumococcal conjugate vaccines with extended serotype coverage), targeting groups at risk for disease and reservoirs for transmission; improving adherence to management guidelines; development of new faster, more accurate diagnostic platforms (e.g. novel point-of-care molecular diagnostics); and development of new adjunctive therapies (aimed at the host-inflammatory response and bacterial virulence factors).

Long-term Vaccine Impact on Invasive Pneumococcal Disease Among Children With Significant Comorbidities in a Large Australian Birth Cohort

BACKGROUND

Little is known about long-term invasive pneumococcal disease (IPD) incidence in children with risk factors (RFs) in populations with high coverage pneumococcal conjugate vaccine (PCV) programs. We measured IPD burden and changes with PCV use in children by RF status.

METHODS

A retrospective cohort of all live births in 2001-2012 in New South Wales, Australia was linked to IPD, hospitalization and death data. RFs were identified from International Classification of Diseases codes in linked hospitalizations. For each RF adjusted hazard ratios (aHRs, using Cox models), population attributable fractions (PAFs) and changes post-PCV relative to baseline for IPD were calculated.

RESULTS

One-thousand two-hundred fifty-one IPD cases occurred in ~1.1 million children in 12-year study cohort. The 75,404 children (6.8% of cohort) with RFs accounted for 255 (20.4%) IPD cases [rate (per 100,000 person-years) of 61 compared with 14 in no RFs]. Asthma was most common RF (n = 41,074; 3.6%) but highest IPD risk was in 2452 children (0.2%) with immunosuppression, splenic dysfunction or breach in cerebrospinal fluid barrier (aHR~20; PAF 0.7-1.8%) versus asthma (aHR 5.3; PAF 14.8%). Compared with 2001-2004 birth cohort (baseline), IPD incidence in PCV-eligible 2009-2012 birth cohort was 78% (95% confidence interval: -72% to -82%) less in children without RFs. IPD declined nonsignificantly (13%; 95% confidence interval: -70% to +138%) in highest IPD risk group, but by 67% (-43% to -82%) in children with other RFs.

CONCLUSIONS

By 8 years of universal PCV, IPD incidence reduced significantly in all children except in the 0.2% at highest risk, for whom antibiotic prophylaxis and additional vaccine doses are recommended but compliance and effectiveness remain uncertain.

Effectiveness of pneumococcal conjugate vaccination against invasive pneumococcal disease among children with and those without HIV infection: a systematic review and meta-analysis

Background

HIV-infected children are at a higher risk of Invasive Pneumococcal Disease (IPD) and its mortality, even in the era of antiretroviral therapy. Therefore, an effective vaccination strategy would be beneficial. To investigate the effectiveness of Pneumococcal Conjugate Vaccination (PCV) against IPD among HIV-Infected and HIV-Uninfected Children through a systematic review and meta-analysis.

Methods

Observational studies and randomized trials on 7 years old or older children were searched in the Cochrane Library, Web of Science core collection, Embase, Medline/PubMed, and Google Scholar. Critical appraisal was done using the Cochrane risk of bias tool and the Newcastle-Ottawa quality assessment form. Effectiveness and efficacy of at least one dose of PCV was investigated among children with and without HIV considering subgroups of pneumococcal serotypes. We meta-analyzed the effect sizes using random-effects modeling.

Results

Efficacy of PCV was estimated as 45.0% (31.2, 56.1) and 52.6% (25.7, 69.8) among HIV-infected and HIV-uninfected children, respectively. Effectiveness of PCV among HIV-infected children as − 6.2% (− 67.6, 32.7) was significantly lower than HIV-uninfected children 65.1% (47.3, 76.9). Effectiveness of PCV among HIV-infected children for IPDs caused by vaccine serotypes was estimated as 7.7(− 66.7, 48.9), and for IPDs caused by non-vaccine serotypes was estimated as − 402.8(− 1856, − 29.2).

Conclusion

Unlike the evidence on the efficacy of PCV against IPD among both of HIV-infected and HIV-uninfected children, its effectiveness against IPD among HIV-infected children is much less limited.

Review registration

The study protocol was registered at PROSPERO (registration ID: CRD42018108187).

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4325-4) contains supplementary material, which is available to authorized users.

Association of Pneumococcal Conjugate Vaccine Coverage With Pneumococcal Meningitis: An Analysis of French Administrative Areas, 2001-2016

Geographic variations of invasive pneumococcal disease incidence and serotype distributions were observed after pneumococcal conjugate vaccine introduction at regional levels and among French administrative areas. The variations could be related to regional vaccine coverage (VC) variations that might have direct consequences for vaccination-policy impact on invasive pneumococcal disease, particularly pneumococcal meningitis (PM) incidence. We assessed vaccine impact from 2001 to 2016 in France by estimating the contribution of regional VC differences to variations of annual local PM incidence. Using a mixed-effect Poisson model, we showed that, despite some variations of VC among administrative areas, vaccine impact on vaccine-serotype PM was homogeneously confirmed among administrative areas. Compared with the prevaccine era, the cumulative VC impact on vaccine serotypes led, in 2016, to PM reductions ranging among regions from 87% (25th percentile) to 91% (75th percentile) for 7-valent pneumococcal conjugate vaccine serotypes and from 58% to 63% for the 6 additional 13-valent pneumococcal conjugate vaccine serotypes. Nonvaccine-serotype PM increases from the prevaccine era ranged among areas from 98% to 127%. By taking into account the cumulative impact of growing VC and VC differences, our analyses confirmed high vaccine impact on vaccine-serotype PM case rates and suggest that VC variations cannot explain PM administrative area differences.

Limited indirect effects of an infant pneumococcal vaccination program in an aging population

BACKGROUND

A general recommendation for adult pneumococcal vaccination with 23-valent polysaccharide vaccine (PPV23) for adults 60 and older has been in place in Germany since 1998, but uptake has been low. Just over a decade after the implementation of an infant pneumococcal conjugate vaccine recommendation, we examined indirect protection effects on adult invasive pneumococcal disease (IPD) in Germany.

METHODS AND FINDINGS

Reported IPD cases decreased in children under two years of age from 11.09 per 100,000 in 2003-2006 to 5.94 per 100,000 in 2017/18, while in adult age groups, reported IPD cases rose across the board, most dramatically in adults 60 years of age and over, from 1.64 to 10.08 cases per 100,000. PCV13-type IPD represents 31% of all cases in this age group, the lion's share of which is due to the rapid increase of serotype 3 IPD, which, by itself, has reached 2.11 reported cases per 100,000 and makes up 21% of all IPD cases in this age group. The two vaccine formulations currently in development (PCV15 and PCV20) would increase current (PCV13) coverage by 8.5% points and 28.0% points in children, while in adults coverage would increase by 10.4% points and 21.9% points, respectively.

CONCLUSIONS

While original models predicted that indirect effects of childhood vaccination would suffice for adults, it seems that the herd protection effect has reached its limit, with vaccine serotypes 4, 19F, and 19A IPD persisting in adults after initial reductions, and serotype 3 IPD not showing any herd protection effect at all.

Progress in mucosal immunization for protection against pneumococcal pneumonia

Introduction: Lower respiratory tract infections are the fourth cause of death worldwide and pneumococcus is the leading cause of pneumonia. Nonetheless, existing pneumococcal vaccines are less effective against pneumonia than invasive diseases and serotype replacement is a major concern. Protein antigens could induce serotype-independent protection, and mucosal immunization could offer local and systemic immune responses and induce protection against pneumococcal colonization and lung infection. Areas covered: Immunity induced in the experimental human pneumococcal carriage model, approaches to address the physiological barriers to mucosal immunization and improve delivery of the vaccine antigens, different strategies already tested for pneumococcal mucosal vaccination, including live recombinant bacteria, nanoparticles, bacterium-like particles, and nanogels as well as, nasal, pulmonary, sublingual and oral routes of vaccination. Expert opinion: The most promising delivery systems are based on nanoparticles, bacterial-like particles or nanogels, which possess greater immunogenicity than the antigen alone and are considered safer than approaches based on living cells or toxoids. These particles can protect the antigen from degradation, eliminating the refrigeration need during storage and allowing the manufacture of dry powder formulations. They can also increase antigen uptake, control release of antigen and trigger innate immune responses.

Spatial analysis of pneumococcal meningitis in São Paulo in the pre- and post-immunization era

OBJECTIVE

To analyze the pneumococcal meningitis incidence rates in the State of São Paulo, Brazil, by age group, municipalities and micro-regions, as well as the spatial distribution of pneumococcal meningitis incidence rates among children under 5 years old in the pre- (2005-2009) and post-vaccination (2011-2013) periods and its associations with socioeconomic variables and vaccination coverage.

METHODS

The data source was the Brazilian Notifiable Diseases Information System. For the pre- and post-vaccination periods, thematic maps were built for pneumococcal meningitis incidence in under-5 children, by São Paulo state micro-regions, vaccination coverage and socioeconomic variables, using QGIS 2.6.1 software. Scan statistics performed by the SatScan 9.2 software were used to analyze spatial and spatiotemporal clusters in São Paulo municipalities and micro-regions. A Bayesian inference for latent Gaussian model with zero-inflated Poisson model through the integrated nested Laplace approximation was used in the spatial analysis to evaluate associations between pneumococcal meningitis incidence rates and socioeconomic variables of interest in São Paulo micro-regions.

RESULTS

From 2005 to 2013, 3,963 pneumococcal meningitis cases were reported in São Paulo. Under-5 children were the most affected in the whole period. In the post-vaccination period, pneumococcal meningitis incidence rates decreased among this population, particularly among infants (from 4.17/100,000 in 2005 to 2.54/100,000 in 2013). Two clusters were found in pre-vaccination - one of low risk for pneumococcal meningitis, in the northwest of the state (OR = 0.45, p = 0.0003); and another of high risk in the southeast (OR = 1.62, p = 0.0000). In the post-vaccination period, only a high-risk cluster remained, in the southeast (RR = 1.97, p = 0.0570). In Bayesian analysis, wealth was the only variable positively associated to pneumococcal meningitis (RR = 1.026, 95%CI 1.002-1.052).

CONCLUSIONS

Pneumococcal meningitis is probably underdiagnosed and underreported in São Paulo. Differentiated rates of pneumococcal meningitis diagnosis and reporting in each microregion, according to the São Paulo Index of Social Responsibility, might explain our results.

Spatial analysis of pneumococcal meningitis in São Paulo in the pre- and post-immunization era

OBJECTIVE

To analyze the pneumococcal meningitis incidence rates in the State of São Paulo, Brazil, by age group, municipalities and micro-regions, as well as the spatial distribution of pneumococcal meningitis incidence rates among children under 5 years old in the pre- (2005-2009) and post-vaccination (2011-2013) periods and its associations with socioeconomic variables and vaccination coverage.

METHODS

The data source was the Brazilian Notifiable Diseases Information System. For the pre- and post-vaccination periods, thematic maps were built for pneumococcal meningitis incidence in under-5 children, by São Paulo state micro-regions, vaccination coverage and socioeconomic variables, using QGIS 2.6.1 software. Scan statistics performed by the SatScan 9.2 software were used to analyze spatial and spatiotemporal clusters in São Paulo municipalities and micro-regions. A Bayesian inference for latent Gaussian model with zero-inflated Poisson model through the integrated nested Laplace approximation was used in the spatial analysis to evaluate associations between pneumococcal meningitis incidence rates and socioeconomic variables of interest in São Paulo micro-regions.

RESULTS

From 2005 to 2013, 3,963 pneumococcal meningitis cases were reported in São Paulo. Under-5 children were the most affected in the whole period. In the post-vaccination period, pneumococcal meningitis incidence rates decreased among this population, particularly among infants (from 4.17/100,000 in 2005 to 2.54/100,000 in 2013). Two clusters were found in pre-vaccination - one of low risk for pneumococcal meningitis, in the northwest of the state (OR = 0.45, p = 0.0003); and another of high risk in the southeast (OR = 1.62, p = 0.0000). In the post-vaccination period, only a high-risk cluster remained, in the southeast (RR = 1.97, p = 0.0570). In Bayesian analysis, wealth was the only variable positively associated to pneumococcal meningitis (RR = 1.026, 95%CI 1.002-1.052).

CONCLUSIONS

Pneumococcal meningitis is probably underdiagnosed and underreported in São Paulo. Differentiated rates of pneumococcal meningitis diagnosis and reporting in each microregion, according to the São Paulo Index of Social Responsibility, might explain our results.

The association between pneumococcal vaccination, ethnicity, and the nasopharyngeal microbiota of children in Fiji

BACKGROUND

Streptococcus pneumoniae is a significant global pathogen that colonises the nasopharynx of healthy children. Pneumococcal conjugate vaccines, which reduce nasopharyngeal colonisation of vaccine-type S. pneumoniae, may have broader effects on the nasopharyngeal microbiota; however, data are limited. In Fiji, nasopharyngeal carriage prevalence of S. pneumoniae and other colonising species differ between the two main ethnic groups. Here, we examined the association between the 7-valent pneumococcal conjugate vaccine (PCV7) and the nasopharyngeal microbiota of children in Fiji, including for each of the two main ethnic groups-indigenous Fijians (iTaukei) and Fijians of Indian descent (FID).

METHOD

The nasopharyngeal microbiota of 132 Fijian children was examined using nasopharyngeal swabs collected from 12-month-old iTaukei and FID children who were vaccinated (3 doses PCV7) or unvaccinated in infancy as part of a phase II randomised controlled trial. Microbiota composition was determined by sequencing the V4 region of the 16S rRNA gene. Species-specific carriage of S. pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus was determined using real-time quantitative PCR. Associations between microbiota composition and other host and environmental factors were considered in the analysis.

RESULTS

PCV7 had no overall impact on microbial diversity or composition. However, ethnic differences were observed in both diversity and composition with iTaukei children having higher relative abundance of Moraxella (p = 0.004) and Haemophilus (p = 0.004) and lower relative abundance of Staphylococcus (p = 0.026), Dolosigranulum (p = 0.004) and Corynebacterium (p = 0.003) compared with FID children. Further, when we stratified by ethnicity, associations with PCV7 could be detected: vaccinated iTaukei children had a lower relative abundance of Streptococcus and Haemophilus compared with unvaccinated iTaukei children (p = 0.022 and p = 0.043, respectively); and vaccinated FID children had a higher relative abundance of Dolosigranulum compared with unvaccinated FID children (p = 0.037). Children with symptoms of an upper respiratory tract infection (URTI) had a significantly different microbiota composition to children without symptoms. The microbiota composition of iTaukei children without URTI symptoms was most similar to the microbiota composition of FID children with URTI symptoms.

CONCLUSIONS

Associations between PCV7 and nasopharyngeal microbiota differed within each ethnic group. This study highlights the influence that ethnicity and URTIs have on nasopharyngeal microbiota.

Nasopharyngeal carriage of Streptococcus pneumoniae serotypes among children in India prior to the introduction of pneumococcal conjugate vaccines: a cross-sectional study

BACKGROUND

Streptococcus pneumoniae is a major cause of pneumonia, meningitis, and other serious infections among children in India. India introduced the 13-valent pneumococcal conjugate vaccine (PCV) in several states in 2017, and is expected to expand to nationwide coverage in the near future. To establish a baseline for measuring the impact of PCV in India, we assessed overall and serotype-specific nasopharyngeal carriage in two pediatric populations.

METHODS

A cross-sectional study was conducted in Palwal District, Haryana, from December 2016 to July 2017, prior to vaccine introduction. Children 2-59 months of age with clinical pneumonia seeking healthcare and those in the community with no clear illness were targeted for enrollment. A nasopharyngeal swab was collected and tested for pneumococcus using conventional culture and sequential multiplex PCR. Isolates were tested for antimicrobial resistance using an E test. Children were considered colonized if pneumococcus was isolated by culture or PCR. The prevalence of pneumococcal and serotype-specific colonization was compared between groups of children using log-binomial regression.

RESULTS

Among 601 children enrolled, 91 had clinical pneumonia and 510 were community children. The proportion colonized with S. pneumoniae was 74.7 and 54.5% among children with clinical pneumonia and community children, respectively (adjusted prevalence ratio: 1.38; 95% confidence interval: 1.19, 1.60). The prevalence of PCV13 vaccine-type colonization was similar between children with clinical pneumonia (31.9%) and community children (28.0%; p = 0.46). The most common colonizing serotypes were 6A, 6B, 14, 19A, 19F, and 23F, all of which are included in the PCV13 vaccine product. Antimicrobial resistance to at least one drug was similar between isolates from children with clinical pneumonia (66.1%) and community children (61.5%; p = 0.49); while resistance to at least two drugs was more common among isolates from children with clinical pneumonia (25.8% vs. 16.4%; p = 0.08). Resistance for all drugs was consistently higher for PCV13 vaccine-type serotypes compared to non-vaccine serotypes in both groups.

CONCLUSION

This study provides baseline information on the prevalence of serotype-specific pneumococcal colonization among children prior to the introduction of PCV in India. Our results suggest a role for pneumococcal vaccines in reducing pneumococcal colonization and antimicrobial resistant isolates circulating in India.

Pneumococcal carriage among adults aged 50 years and older with co-morbidities attending medical practices in Rome, Italy

BACKGROUND

Data on Streptococcus pneumoniae carriage in adults with co-morbidities are limited. In this study we estimated the pneumococcal carriage among adults with co-morbidities and evaluated socio-demographic and clinical risk factors. The potential coverage of the current pneumococcal vaccines recommended for adults (PCV13 and PPV23) was also investigated.

METHODS

A cross-sectional study on S. pneumoniae carriage among unvaccinated adults ≥50 years with co-morbidities, presenting with or without acute respiratory symptoms at general practitioners in Rome, Italy, between October 2015 and July 2016 was conducted. Pneumococcal carriage was investigated by both cultural and molecular methods. Socio-demographic variables and co-morbidities were evaluated by logistic models as possible risk factors for pneumococcal carriage.

RESULTS

Out of 248 patients (median age: 73 yrs; IQR: 65-79), 12 (4.8%) and 83 (33.5%) individuals were found colonized using cultural or molecular methods, respectively. Potential risk factors for pneumococcal colonization as ascertained by molecular methods were: low level of education (adjusted OR = 3.71, 95% CI: 1.62-9.40), winter months (December-March vs other months, adjusted OR = 2.56, 95% CI: 1.29-5.14), and presence of chronic lung diseases (adjusted OR = 2.18, 95% CI: 1.15-4.16). The combination of serotype-specific multiplex RT-PCR and conventional PCR allowed to identify 22 serotypes/group of serotypes, of which the most common were: 24F/24A/24B, 12F/12A/12B/44/46, 6A/6B, 14, 15B/15C, and 22F/22A. Prevalence of pneumococcal carriage due to PCV13 serotypes and non-PCV13 serotypes was 23.6% and 67.3%, respectively. Prevalence of colonization due to PPV23 serotypes was estimated to be 54.6%.

CONCLUSIONS

A high prevalence of S. pneumoniae carriage was observed among adults with co-morbidities, especially among individuals affected by chronic lung diseases. These results support vaccine strategies based on the sequential administration of PCV13 and PPV23 to control potentially invasive pneumococcal strains in adults, especially in subjects with co-morbidities.

Past and Current Perspectives in Modeling Bacteria and Blood-Brain Barrier Interactions

The central nervous system (CNS) barriers are highly specialized cellular barriers that promote brain homeostasis while restricting pathogen and toxin entry. The primary cellular constituent regulating pathogen entry in most of these brain barriers is the brain endothelial cell (BEC) that exhibits properties that allow for tight regulation of CNS entry. Bacterial meningoencephalitis is a serious infection of the CNS and occurs when bacteria can cross specialized brain barriers and cause inflammation. Models have been developed to understand the bacterial - BEC interaction that lead to pathogen crossing into the CNS, however, these have been met with challenges due to these highly specialized BEC phenotypes. This perspective provides a brief overview and outlook of the in vivo and in vitro models currently being used to study bacterial brain penetration, and opinion on improved models for the future.

Unveiling the Importance of Amide Protons in CSP:ComD Interactions in Streptococcus pneumoniae

Streptococcus pneumoniae is an opportunistic pathogen that can cause diseases ranging from mild respiratory infections to life-threatening conditions such as pneumonia, meningitis, and bacteremia. S. pneumoniae pathogenicity is dependent on the action of a 17-amino acid peptide pheromone, termed competence stimulating peptide (CSP) that controls the competence regulon, a quorum sensing (QS) circuit. Therefore, intercepting QS could have therapeutic implications in treating pneumococcal infections while avoiding emerging antimicrobial resistance. In this study, we set out to evaluate the impact of amide protons on CSP activity and metabolic stability through systematic N-methylation. Our results indicate that the majority of amide protons are critical for CSP activity, either through direct interactions with the cognate receptor or by stabilizing the bioactive conformation. Importantly, we identified several N-methyl CSP analogs, namely, CSP1(15)-N-Me-K6 and CSP1(15)-N-Me-F7, that retain their biological activity while exhibiting enhanced metabolic stability. These analogs are privileged scaffolds for the design of CSP-based QS modulators with drug-like properties.

Vaccines to Prevent Pneumococcal Community-Acquired Pneumonia

Streptococcus pneumoniae is the most frequent pathogen in community-acquired pneumonia and also causes invasive diseases like bacteremia and meningitis. Young children and elderly are especially at risk for pneumococcal diseases and are, therefore, eligible for pneumococcal vaccination in most countries. This reviews provides an overview of the current epidemiology of pneumococcal infections, history and evidence of available pneumococcal polysaccharide and conjugate vaccines, and current recommendations.

The impact of childhood pneumococcal vaccination on hospital admissions in England: a whole population observational study

Background

Pneumococcal infections are major causes of morbidity and mortality worldwide. We use routine hospital admissions data and time-series modelling analysis to estimate the impact of the seven and thirteen valent pneumococcal conjugate vaccines (PCV7 and PCV13) on hospital admissions due to pneumococcal disease in England.

Methods

Hospital admissions for pneumococcal meningitis, bacteraemia and pneumonia between January 1, 2003 and December 31, 2015 were identified from the national Hospital Episode Statistics database for all age groups in England. We model the impact of pneumococcal vaccination using interrupted time series analysis. Hospital admissions prior to vaccine introduction were extrapolated to predict the expected number of admissions in the absence of pneumococcal vaccines. Admissions avoided over time were estimated by comparing the fitted interrupted time series and the expected model for no vaccination in a Bayesian framework.

Results

Overall, there were 43,531 (95% credible interval (CrI): 36486–51,346) fewer hospital admissions due to bacteraemia, meningitis and pneumonia in England during the period from 2006 to 2015 than would have been expected if pneumococcal vaccines had not been implemented, with the majority of hospital admissions avoided due to pneumonia. Among young children reductions in meningitis were more common, while among adults reductions in pneumonia admissions were relatively more important, with no evidence for reduced bacteraemia and meningitis among older adults. We estimated that 981 (95% CrI: 391–2018), 749 (95% CrI: 295–1442) and 1464 (95% CrI: 793–2522) bacteraemia, meningitis and pneumonia related hospital admissions, respectively, were averted in children < 2 years of age.

Conclusions

Substantial reductions in hospital admissions for bacteraemia, meningitis and pneumonia in England were estimated after the introduction of childhood vaccination, with indirect effects being responsible for most of the hospital admissions avoided.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4119-8) contains supplementary material, which is available to authorized users.

Serotype distribution and antibiotic resistance among invasive Streptococcus pneumoniae from Oman post 13-valent vaccine introduction

OBJECTIVE

This study was undertaken to determine the serotype distribution and drug susceptibility patterns in pneumococcal isolates recovered from patients with invasive pneumococcal disease (IPD).

METHODS

All invasive pneumococcal isolates received between June 2014 and June 2016 were included in the study as part of a national laboratory-based IPD surveillance program. Isolates recovered from clinical specimens of normally sterile body sites were included.

RESULTS

A total of 41 different serotypes were identified among the 132 pneumococcal isolates included in this study. The most prevalent serotypes/serogroups were 12 (8.3%), 15 (8.3%), 19F (7.6%), 3 (6.1%), and 19A (6.1%);. It was observed that overall vaccine coverage rates for pneumococcal conjugate vaccines (PCV), PCV7, PCV10 and PCV13 were 15.9%, 24.2% and 37.1% respectively. 56.8% (n=75) of the isolates were non-susceptible to at least one antibiotic and 40.9% (n=54) of the isolates were resistant to PEN (M). 18.9% (n=25) of the isolates were multi-drug resistant (MDR).The case fatality rate was 15.9%.

CONCLUSION

Our study results call for broader vaccine coverage, emphasizes the need to introduce the conjugate pneumococcal vaccine for the high risk adult population and stress the importance of continuous surveillance of serotypes and antimicrobial resistance to guide vaccine development and antimicrobial stewardship activities.

Streptococcus pneumoniae: Invasion and Inflammation

Streptococcus pneumoniae (the pneumoccus) is the leading cause of otitis media, community-acquired pneumonia, and bacterial meningitis. The success of the pneumococcus stems from its ability to persist in the population as a commensal and avoid killing by immune system. This chapter first reviews the molecular mechanisms that allow the pneumococcus to colonize and spread from one anatomical site to the next. Then, it discusses the mechanisms of inflammation and cytotoxicity during emerging and classical pneumococcal infections.

Preventive effects of pneumococcal and influenza vaccines on community-acquired pneumonia in older individuals in Japan: a case-control study

At present, there are few reports that have clarified the effectiveness of 23-valent pneumococcal polysaccharide vaccine (PPSV23) against all-cause pneumonia or pneumococcal pneumonia in community-acquired pneumonia (CAP) in older individuals in Japan. We conducted a hospital-based matched case-control study to investigate separately the preventive effects of PPSV23 and trivalent influenza vaccine (TIV) on all-cause CAP and pneumococcal CAP in older individuals in Japan. Cases were individuals aged 65 years or older who were newly diagnosed with CAP from October 2010 to September 2014. Two control patients with a different disease (one respiratory medicine and one non-respiratory medicine) matched for sex, age, date of outpatient visit, and medical institution were selected for each case. Odds ratios (ORs) and 95% confidence intervals (CIs) of PPSV23 and TIV for the occurrence of all-cause CAP and pneumococcal CAP were calculated using conditional and unconditional logistic regression models. The analysis included 161 cases and 308 controls from the 4-year period. The adjusted OR for the occurrence of all-cause CAP was 0.76 (95%CI = 0.44-1.32) with PPSV23 vaccination and 0.79 (95%CI = 0.50-1.25) with TIV vaccination compared with unvaccinated individuals. When the outcome index was restricted to pneumococcal CAP, the adjusted OR significantly decreased to 0.23 (95%CI = 0.08-0.66) with PPSV23 vaccination, but not with TIV vaccination (adjusted OR = 0.65, 95%CI = 0.31-1.36). PPSV23 vaccination is likely effective in reducing incidence of pneumococcal CAP in older individuals, although its preventive effect for all-cause CAP has not been achieved.

Burden of Streptococcus pneumoniae and Haemophilus influenzae type b disease in children in the era of conjugate vaccines: global, regional, and national estimates for 2000-15

Background

Pneumococcal conjugate vaccine (PCV) and Haemophilus influenzae type b (Hib) vaccine are now used in most countries. To monitor global and regional progress towards improving child health and to inform national policies for disease prevention and treatment, we prepared global, regional, and national disease burden estimates for these pathogens in children from 2000 to 2015.

Methods

Using WHO and Maternal and Child Epidemiology Estimation collaboration country-specific estimates of pneumonia and meningitis mortality and pneumonia morbidity from 2000 to 2015, we applied pneumococcal and Hib cause-specific proportions to estimate pathogen-specific deaths and cases. Summary estimates of the proportion of pneumonia deaths and cases attributable to these pathogens were derived from four Hib vaccine and six PCV efficacy and effectiveness study values. The proportion of meningitis deaths due to each pathogen was derived from bacterial meningitis aetiology and adjusted pathogen-specific meningitis case–fatality data. Pneumococcal and Hib meningitis cases were inferred from modelled pathogen-specific meningitis deaths and literature-derived case–fatality estimates. Cases of pneumococcal and Hib syndromes other than pneumonia and meningitis were estimated using the ratio of pathogen-specific non-pneumonia, non-meningitis cases to pathogen-specific meningitis cases from the literature. We accounted for annual HIV infection prevalence, access to care, and vaccine use.

Findings

We estimated that there were 294 000 pneumococcal deaths (uncertainty range [UR] 192 000–366 000) and 29 500 Hib deaths (18 400–40 700) in HIV-uninfected children aged 1–59 months in 2015. An additional 23 300 deaths (15 300–28 700) associated with pneumococcus and fewer than 1000 deaths associated Hib were estimated to have occurred in children infected with HIV. We estimate that pneumococcal deaths declined by 51% (7–74) and Hib deaths by 90% (78–96) from 2000 to 2015. Most children who died of pneumococcus (81%) and Hib (76%) presented with pneumonia. Less conservative assumptions result in pneumococcccal death estimates that could be as high as 515 000 deaths (302 000–609 000) in 2015. Approximately 50% of all pneumococcal deaths in 2015 occurred in four countries in Africa and Asia: India (68 700 deaths, UR 44 600–86 100), Nigeria (49 000 deaths, 32 400–59 000), the Democratic Republic of the Congo (14 500 deaths, 9300–18 700), and Pakistan (14 400 deaths, 9700–17 000]). India (15 600 deaths, 9800–21 500), Nigeria (3600 deaths, 2200–5100), China (3400 deaths, 2300–4600), and South Sudan (1000 deaths, 600–1400) had the greatest number of Hib deaths in 2015. We estimated 3·7 million episodes (UR 2·7 million–4·3 million) of severe pneumococcus and 340 000 episodes (196 000–669 000) of severe Hib globally in children in 2015.

Interpretation

The widespread use of Hib vaccine and the recent introduction of PCV in countries with high child mortality is associated with reductions in Hib and pneumococcal cases and deaths. Uncertainties in the burden of pneumococcal disease are largely driven by the fraction of pneumonia deaths attributable to pneumococcus. Progress towards further reducing the global burden of Hib and pneumococcal disease burden will depend on the efforts of a few large countries in Africa and Asia.

Funding

Bill & Melinda Gates Foundation.

Microbiome as a tool and a target in the effort to address antimicrobial resistance

Reciprocal, intimate relationships between the human microbiome and the host immune system are shaped by past microbial encounters and prepare the host for future ones. Antibiotics and other antimicrobials leave their mark on both the microbiome and host immunity. Antimicrobials alter the structure of the microbiota, expand the host-specific pool of antimicrobial-resistance genes and organisms, degrade the protective effects of the microbiota against invasion by pathogens, and may impair vaccine efficacy. Through these effects on the microbiome they may affect immune responses. Vaccines that exert protective or therapeutic effects against pathogens may reduce the use of antimicrobials, the development and spread of antimicrobial resistance, and the harmful impacts of these drugs on the microbiome. Other strategies involving manipulation of the microbiome to deplete antibiotic-resistant organisms or to enhance immune responses to vaccines may prove valuable in addressing antimicrobial resistance as well. This article describes the intersections of immunity, microbiome and antimicrobial exposure, and the use of vaccines and other alternative strategies for the control and management of antimicrobial resistance.