Rebound in the incidence of pneumococcal meningitis in northern France: effect of serotype replacement

Stable Incidence of Invasive Pneumococcal Disease in Children in Northern France From 2014 Through 2018

BACKGROUND

The 13-valent pneumococcal conjugate vaccine (PCV13) has been recommended in France since June 2010. The aim of this study was to evaluate the trends in the incidence of invasive pneumococcal disease (IPD) resulting in hospitalization of children younger than 18 years of age, to identify the vaccination status of these patients and to analyze the serotypic evolution of the pneumococci involved in the various types of IPD.

METHODS

This multicenter retrospective study reviewed all admissions of children younger than 18 years of age for IPD from 2014 through 2018 in all hospitals with a pediatric or neonatal unit in northern France. Data completeness was obtained by matching 3 independent databases. The incidence of IPD resulting in hospitalization was calculated per age group. The clinical course and the vaccine and nonvaccine types were described overall and by the IPD type.

RESULTS

One hundred thirty cases of IPD were identified: 51 with bacteremia, 45 meningitis, 28 pneumonia or pleuropneumonia and 6 arthritis. The IPD incidence ranged from 2.4 to 3.0/100,000 in children under 18 years of age (95% confidence intervals, 1.4-3.3 and 1.9-4.1, respectively), and from 9.5 to 15.9/100,000 in children under 2 years of age, with no significant differences over time. Nonvaccine types were predominant (81%), mainly 24F, 23B and 10A. Vaccine serotype 3 was involved in 10 cases of IPD, 2 of which were in correctly vaccinated children. Two cases of IPD could have been prevented by vaccination. Neurologic sequelae affected 26% of these children (62% of those with meningitis). Six children died from IPD (5%).

CONCLUSION

The incidence of IPD resulting in hospitalization remained stable in northern France during the study period, with no significant increase in nonvaccine types. Further surveillance is needed to adjust the vaccination strategy if necessary.

Synthetic Analogs of Streptococcus pneumoniae Capsular Polysaccharides and Immunogenic Activities of Glycoconjugates

Streptococcus pneumoniae is a Gram-positive bacterium (pneumococcus) that causes severe diseases in adults and children. It was established that some capsular polysaccharides of the clinically significant serotypes of S. pneumoniae in the composition of commercial pneumococcal polysaccharide or conjugate vaccines exhibit low immunogenicity. The review considers production methods and structural features of the synthetic oligosaccharides from the problematic pneumococcal serotypes that are characterized with low immunogenicity due to destruction or detrimental modification occurring in the process of their preparation and purification. Bacterial serotypes that cause severe pneumococcal diseases as well as serotypes not included in the composition of the pneumococcal conjugate vaccines are also discussed. It is demonstrated that the synthetic oligosaccharides corresponding to protective glycotopes of the capsular polysaccharides of various pneumococcal serotypes are capable of inducing formation of the protective opsonizing antibodies and immunological memory. Optimal constructs of oligosaccharides from the epidemiologically significant pneumococcal serotypes are presented that can be used for designing synthetic pneumococcal vaccines, as well as test systems for diagnosis of S. pneumoniae infections and monitoring of vaccination efficiency .

Oligodeoxynucleotides containing unmethylated cytosine-guanine motifs are effective immunostimulants against pneumococcal meningitis in the immunocompetent and neutropenic host

BACKGROUND

Bacterial meningitis is a fatal disease with a mortality up to 30% and neurological sequelae in one fourth of survivors. Available vaccines do not fully protect against this lethal disease. Here, we report the protective effect of synthetic oligodeoxynucleotides containing unmethylated cytosine-guanine motifs (CpG ODN) against the most frequent form of bacterial meningitis caused by Streptococcus pneumoniae.

METHODS

Three days prior to the induction of meningitis by intracerebral injection of S. pneumoniae D39, wild-type and Toll-like receptor (TLR9)^-/- mice received an intraperitoneal injection of 100 μg CpG ODN or vehicle. To render mice neutropenic, anti-Ly-6G monoclonal antibody was daily administrated starting 4 days before infection with a total of 7 injections. Kaplan-Meier survival analyses and bacteriological studies, in which mice were sacrificed 24 h and 36 h after infection, were performed.

RESULTS

Pre-treatment with 100 μg CpG ODN prolonged survival of immunocompetent and neutropenic wild-type mice but not of TLR9^-/- mice. There was a trend towards lower mortality in CpG ODN-treated immunocompetent and neutropenic wild-type mice. CpG ODN caused an increase of IL-12/IL-23p40 levels in the spleen and serum in uninfected animals. The effects of CpG ODN on bacterial concentrations and development of clinical symptoms were associated with an increased number of microglia in the CNS during the early phase of infection. Elevated concentrations of IL-12/IL-23p40 and MIP-1α correlated with lower bacterial concentrations in the blood and spleen during infection.

CONCLUSIONS

Pre-conditioning with CpG ODN strengthened the resistance of neutropenic and immunocompetent mice against S. pneumoniae meningitis in the presence of TLR9. Administration of CpG ODN decreased bacterial burden in the cerebellum and reduced the degree of bacteremia. Systemic administration of CpG ODN may help to prevent or slow the progression to sepsis of bacterial CNS infections in healthy and immunocompromised individuals even after direct inoculation of bacteria into the intracranial compartments, which can occur after sinusitis, mastoiditis, open head trauma, and surgery, including placement of an external ventricular drain.

Searching for Antipneumococcal Targets: Choline-Binding Modules as Phagocytosis Enhancers

Choline-binding proteins (CBPs) from Streptococcus pneumoniae comprise a family of modular polypeptides involved in essential events of this pathogen. They recognize the choline residues present in the teichoic and lipoteichoic acids of the cell wall using the so-called choline-binding modules (CBMs). The importance of CBPs in pneumococcal physiology points to them as novel targets to combat antimicrobial resistances shown by this organism. In this work we have tested the ability of exogenously added CBMs to act as CBP inhibitors by competing with the latter for the binding to the choline molecules in the bacterial surface. First, we carried out a thorough physicochemical characterization of three native CBMs, namely C-LytA, C-Cpl1, and C-CbpD, and assessed their affinity for choline and macromolecular, pneumococcal cell-wall mimics. The interaction with these substrates was evaluated by molecular modeling, analytical ultracentrifugation, surface plasmon resonance, and fluorescence and circular dichroism spectroscopies. Van't Hoff thermal analyses unveiled the existence of one noncanonical choline binding site in each of the C-Cpl1 and C-CbpD proteins, leading in total to 5 ligand-binding sites per dimer and 4 sites per monomer, respectively. Remarkably, the binding affinities of the CBMs do not directly correlate with their native oligomeric state or with the number of choline-binding sites, suggesting that choline recognition by these modules is a complex phenomenon. On the other hand, the exogenous addition of CBMs to pneumococcal planktonic cultures caused extensive cell-chaining probably as a consequence of the inhibition of CBP attachment to the cell wall. This was accompanied by bacterial aggregation and sedimentation, causing an enhancement of bacterial phagocytosis by peritoneal macrophages. In addition, the rational design of an oligomeric variant of a native CBM led to a substantial increase in its antibacterial activity by multivalency effects. These results suggest that CBMs might constitute promising nonlytic antimicrobial candidates based on the natural induction of the host defense system.

New Strategy Is Needed to Prevent Pneumococcal Meningitis

BACKGROUND

Polysaccharide conjugate vaccines (PCVs) target the pneumococcal capsular types that most commonly cause fatal pneumonia and sepsis. Because these types were eliminated by the vaccines, it became apparent that in immunized populations, most invasive pneumococcal diseases, including bacteremia, sepsis and complicated pneumonia, were greatly reduced. However, the protective effects of PCVs against another invasive disease, meningitis, has shown much less or no decrease in disease incidence.

METHODS

References were identified through searches of PubMed for articles published from January 1930 to the present by use of specific search terms. Relevant articles were also identified through searches in Google and Google Scholar. Relevant references cited in those articles were also reviewed.

RESULTS

Even in the presence of the PCVs, meningitis rates in children have been reported globally to be as high as 13 per 100,000 annually. Widespread use of vaccines resulted in the emergence of a broad diversity of replacement non-PCV type strains. These strains generally failed to cause sepsis, but caused meningitis of comparable severity and levels similar to, or in excess of, prior pneumococcal meningitis rates. This is probably because these non-PCV type strains do not survive well in the blood, therefore possibly entering the brain through nonhematogenous routes.

CONCLUSIONS

Because virtually all cases of pneumococcal meningitis lead to either permanent neurologic sequelae or death, it would be well worth the effort to develop a new vaccine capable of preventing pneumococcal meningitis regardless of capsular type. Such a vaccine would need to protect against colonization with most, if not all, pneumococci.

Effect of Pneumococcal Conjugate Vaccines on Pneumococcal Meningitis, England and Wales, July 1, 2000-June 30, 2016

We describe the effects of the 7-valent (PCV7) and 13-valent (PCV13) pneumococcal conjugate vaccines on pneumococcal meningitis in England and Wales during July 1, 2000–June 30, 2016. Overall, 84,473 laboratory-confirmed invasive pneumococcal disease cases, including 4,160 (4.9%) cases with meningitis, occurred. PCV7 implementation in 2006 did not lower overall pneumococcal meningitis incidence because of replacement with non–PCV7-type meningitis incidence. Replacement with PCV13 in 2010, however, led to a 48% reduction in pneumococcal meningitis incidence by 2015–16. The overall case-fatality rate was 17.5%: 10.7% among patients <5 years of age, 17.3% among patients 5–64 years of age, and 31.9% among patients >65 years of age. Serotype 8 was associated with increased odds of death (adjusted odds ratio 2.9, 95% CI 1.8–4.7). In England and Wales, an effect on pneumococcal meningitis was observed only after PCV13 implementation. Further studies are needed to assess pneumococcal meningitis caused by the replacing serotypes.

Serotype distribution of Streptococcus pneumoniae causing invasive disease in children in the post-PCV era: A systematic review and meta-analysis

BACKGROUND

Routine immunisation with pneumococcal conjugate vaccines (PCV7/10/13) has reduced invasive pneumococcal disease (IPD) due to vaccine serotypes significantly. However, an increase in disease due to non-vaccine types, or serotype replacement, has been observed. Serotypes' individual contributions to IPD play a critical role in determining the overall effects of PCVs. This study examines the distribution of pneumococcal serotypes in children to identify leading serotypes associated with IPD post-PCV introduction.

METHODS

A systematic search was performed to identify studies and surveillance reports (published between 2000 and December 2015) of pneumococcal serotypes causing childhood IPD post-PCV introduction. Serotype data were differentiated based on the PCV administered during the study period: PCV7 or higher valent PCVs (PCV10 or PCV13). Meta-analysis was conducted to estimate the proportional contributions of the most frequent serotypes in childhood IPD in each period.

RESULTS

We identified 68 studies reporting serotype data among IPD cases in children. We analysed data from 38 studies (14 countries) where PCV7 was administered and 20 (24 countries) where PCV10 or PCV13 have been introduced. Studies reported early and late periods of PCV7 administration (range: 2001∓13). In these settings, serotype 19A was the most predominant cause of childhood IPD, accounting for 21.8% (95%CI 18.6∓25.6) of cases. In countries that have introduced higher valent PCVs, study periods were largely representative of the transition and early years of PCV10 or PCV13. In these studies, the overall serotype-specific contribution of 19A was lower (14.2% 95%CI 11.1∓18.3). Overall, non-PCV13 serotypes contributed to 42.2% (95%CI 36.1∓49.5%) of childhood IPD cases. However, regional differences were noted (57.8% in North America, 71.9% in Europe, 45.9% in Western Pacific, 28.5% in Latin America, 42.7% in one African country, and 9.2% in one Eastern Mediterranean country). Predominant non-PCV13 serotypes overall were 22F, 12F, 33F, 24F, 15C, 15B, 23B, 10A, and 38 (descending order), but their rank order varied by region.

CONCLUSION

Childhood IPD is associated with a wide number of serotypes. In the early years after introduction of higher valent PCVs, non-PCV13 types caused a considerable proportion of childhood IPD. Serotype data, particularly from resource-limited countries with high burden of IPD, are needed to assess the importance of serotypes in different settings. The geographic diversity of pneumococcal serotypes highlights the importance of continued surveillance to guide vaccine design and recommendations.

Choline Binding Proteins from Streptococcus pneumoniae: A Dual Role as Enzybiotics and Targets for the Design of New Antimicrobials

Streptococcus pneumoniae (pneumococcus) is an important pathogen responsible for acute invasive and non-invasive infections such as meningitis, sepsis and otitis media, being the major cause of community-acquired pneumonia. The fight against pneumococcus is currently hampered both by insufficient vaccine coverage and by rising antimicrobial resistances to traditional antibiotics, making necessary the research on novel targets. Choline binding proteins (CBPs) are a family of polypeptides found in pneumococcus and related species, as well as in some of their associated bacteriophages. They are characterized by a structural organization in two modules: a functional module (FM), and a choline-binding module (CBM) that anchors the protein to the choline residues present in the cell wall through non-covalent interactions. Pneumococcal CBPs include cell wall hydrolases, adhesins and other virulence factors, all playing relevant physiological roles for bacterial viability and virulence. Moreover, many pneumococcal phages also make use of hydrolytic CBPs to fulfill their infectivity cycle. Consequently, CBPs may play a dual role for the development of novel antipneumococcal drugs, both as targets for inhibitors of their binding to the cell wall and as active cell lytic agents (enzybiotics). In this article, we review the current state of knowledge about host- and phage-encoded pneumococcal CBPs, with a special focus on structural issues, together with their perspectives for effective anti-infectious treatments.

Vaccine preventable meningitis in Malaysia: epidemiology and management

Worldwide bacterial meningitis accounts for more than one million cases and 135,000 deaths annually. Profound, lasting neurological complications occur in 9-25% of cases. This review confirms the greatest risk from bacterial meningitis is in early life in Malaysia. Much of the disease burden can be avoided by immunization, particularly against Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae. Despite inclusion of the Hib vaccine in the National Immunisation Programme and the licensure of pneumococcal vaccines, these two species are the main contributors to bacterial meningitis in Malaysia, with Neisseria meningitidis and Mycobacterium tuberculosis, causing a smaller proportion of disease. The high Hib prevalence may partly be due to dated, small-scale studies limiting the understanding of the current epidemiological situation. This highlights the need for larger, better quality surveillance from Malaysia to evaluate the success of Hib immunization and to help guide immunization policy for vaccines against S. pneumoniae and N. meningitidis.

Longitudinal DRG-based survey of all-cause and pneumococcal pneumonia and meningitis for inpatients in France (2005-2010)

OBJECTIVE

This population-based retrospective study quantified the burden of all-cause and pneumococcal pneumonia and meningitis in the Rhône-Alpes region of France from 2005 to 2010, when the 7-valent pneumococcal conjugate vaccine uptake increased from 50 to>90% in children.

PATIENTS AND METHODS

Hospital admission data was obtained from the French Diagnosis Related Groups program database (French acronym PMSI). Patients were residents of the Rhône-Alpes region hospitalized for the diseases of interest during 2005-2010. Hospitalization and in-hospital mortality rates were calculated by age, sex, and year on the basis of the Rhône-Alpes region population. Hospitalization and in-hospital mortality rates were compared using Chi(2) tests with statistical significance adjusted for multiple comparisons.

RESULTS

The highest hospitalization rates by age group were: all-cause pneumonia, oldest group (>65 years); all-cause and pneumococcal meningitis, youngest group (0-4 years), and pneumococcal pneumonia, youngest and oldest groups. Hospitalization rates significantly decreased for all-cause pneumonia (5-19 years: -12.71%) and all-cause meningitis (20-49 years: -29.22%). Pneumococcal disease rates did not significantly change in any age group. Mortality rates from all-cause pneumonia and meningitis were highest in the oldest age groups.

CONCLUSIONS

The burden of all-cause and pneumococcal pneumonia and meningitis remains substantial. Significant changes (decreases) between 2005 and 2010 in hospitalization rates were limited and varied among age groups, most likely because this study began 2 years after PCV7 was first introduced in France for children at broadly-defined high risk. Further research is needed on the relationship between serotype epidemiology and clinical patterns of disease.

Impact of the 13-valent pneumococcal conjugate vaccine on the incidence of pneumococcal meningitis in children

The impact of the 13-valent pneumococcal conjugate vaccine (PCV13) on the incidence of pneumococcal meningitis (PM) in children is unknown. To determine this impact, a descriptive multicentre retrospective cohort study was conducted from 2008 to 2013 in northern France. All laboratory-confirmed PM in children aged <18 years in all hospitals of the area with paediatric units were included. Two independent databases were used for exhaustive identification of cases: medical plus laboratory records at each hospital and discharge codes. The corrected incidence of PM was determined by a capture-recapture analysis using these two databases. Sixty-two cases were found over the 6-year period. A decrease of the PM corrected incidence was observed in the global population (P = 0·07), significant only for children aged <2 years, from 11·9/100 000 in 2008 in 1·9/100 000 in 2013 [6·4 fold-decrease, 95% confidence interval (CI) 1·4-41, P = 0·01] between years 2008 and 2013. When comparing the pre- and post-PCV13 periods, this decrease was still statistically significant for children aged <2 years [7·32/100 000 (95% CI 4·39-10·25) to 2·78/100 000 (95% CI 0·96-4·60), P = 0·01]. Only three (5%) cases of PM caused by vaccine serotypes could have been prevented. After the introduction of the PCV13 vaccine, a decrease in the incidence of PM cases in children in northern France was observed.

Interaction of Vaccination and Reduction of Antibiotic Use Drives Unexpected Increase of Pneumococcal Meningitis

Antibiotic-use policies may affect pneumococcal conjugate-vaccine effectiveness. The reported increase of pneumococcal meningitis from 2001 to 2009 in France, where a national campaign to reduce antibiotic use was implemented in parallel to the introduction of the 7-valent conjugate vaccine, provides unique data to assess these effects. We constructed a mechanistic pneumococcal transmission model and used likelihood to assess the ability of competing hypotheses to explain that increase. We find that a model integrating a fitness cost of penicillin resistance successfully explains the overall and age-stratified pattern of serotype replacement. By simulating counterfactual scenarios of public health interventions in France, we propose that this fitness cost caused a gradual and pernicious interaction between the two interventions by increasing the spread of nonvaccine, penicillin-susceptible strains. More generally, our results indicate that reductions of antibiotic use may counteract the benefits of conjugate vaccines introduced into countries with low vaccine-serotype coverages and high-resistance frequencies. Our findings highlight the key role of antibiotic use in vaccine-induced serotype replacement and suggest the need for more integrated approaches to control pneumococcal infections.

Pneumococcal meningitis and vaccine effects in the era of conjugate vaccination: results of 20 years of nationwide surveillance in Germany

Background

Long-term complications and a case mortality rate of 7.5% make meningitis caused by Streptococcus pneumoniae a serious clinical threat. In 2006, a general pneumococcal conjugate vaccination (PCV) recommendation was issued for all children under 2 years in Germany. Here, we investigate serotype changes in meningitis cases after this vaccine recommendation.

Methods

The German National Reference Center for Streptococci (NRCS) has conducted surveillance for invasive pneumococcal disease (IPD) in Germany since 1992. Pneumococcal isolates were serotyped by the Neufeld’s Quellung reaction and antibiotic susceptibility was tested using the broth microdilution method.

Results

Of 22,204 IPD isolates sent to the NRCS from July 1992 to June 2013, 3,086 were meningitis cases. Microbiological and statistical investigations were performed to characterize and quantify all meningitis cases, focusing on changes reflecting implementation of the national PCV recommendation. 1,766 isolates (57.2% of meningitis cases) were from adults (≥16 years) and 1,320 isolates (42.8%) originated from children (<16 years). Overall, the leading serotypes were 14 (9.7%), 7F (7.8%), 3 (6.9%), 19F (5.7%) and 23F (5.0%). Among children, serotypes 14 (16.2%), 7F (8.9%) and 19F (7.1%) were most common, whereas among adults, serotypes 3 (9.6%), 7F (6.9%), 22F (5.0%), 23F (4.9%) and 14 (4.8%) were most prevalent. After the introduction of general PCV7/10/13 vaccination a significant decrease for most vaccine serotypes was observed. Generally, the differences in antibiotic nonsusceptibility between children <16 years and adults ≥16 were low. For macrolides in the pre-PCV7 period, a significantly higher proportion of resistant isolates was found in children (25.1%), compared to the post-vaccination period (9.7%; p<0.0001).

Conclusions

Implementation of the pneumococcal conjugate vaccines broadly reduced vaccine-type meningitis cases. Changes in serotype prevalence must be continuously monitored to observe future trends concerning pneumococcal meningitis.

Guidelines for the management of suspected and confirmed bacterial meningitis in Canadian children older than one month of age

The incidence of bacterial meningitis in infants and children has decreased since the routine use of conjugated vaccines targeting Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis. However, this infection continues to be associated with considerable mortality and morbidity if not treated effectively with empirical antimicrobial therapy. Diagnosis still rests on clinical signs and symptoms, and cerebrospinal fluid analysis. This position statement outlines the rationale for current recommended empirical therapy using a third-generation cephalosporin and vancomycin for suspected bacterial meningitis. It also provides new recommendations for the use of adjuvant corticosteroids in this setting. Once antibiotic susceptibilities of the pathogen are known, antimicrobials should be reviewed and modified accordingly. Recommendations for treatment duration as well as audiology testing are included. The present statement replaces a previous Canadian Paediatric Society position statement on bacterial meningitis published in 2007 and revised in 2008.

A review of the impact of pneumococcal polysaccharide conjugate vaccine (7-valent) on pneumococcal meningitis

INTRODUCTION

Streptococcus pneumoniae is the leading cause of bacterial meningitis. Young children, the elderly and those who are immunocompromised or who suffer from chronic diseases have the highest risk of developing pneumococcal meningitis. A 7-valent pneumococcal conjugate vaccine (PCV7) was licensed in 2000 in the US and in 2001 in Europe.

METHODS

A literature search was performed in PubMed to identify studies assessing the impact of routine childhood PCV7 vaccination on pneumococcal diseases. Here, we report the impact on pneumococcal meningitis.

RESULTS

A total of 17 articles reporting impact data on pneumococcal meningitis were included in this review: 11 from Western Europe and 6 from North America. In the post-vaccination period, compared with the pre-vaccination period, a reduction ranging from 59.2% in the US, 1 year after vaccine introduction, to 100% in Belgium, 4 years after vaccine introduction in vaccine-type (VT) pneumococcal meningitis incidence was reported in vaccine-eligible children in seven studies. In addition, the majority of studies reported reductions in VT and all-type pneumococcal meningitis incidence in age groups that were not vaccine-eligible.

CONCLUSIONS

The results from this review demonstrate that PCV7 has had a significant impact on pneumococcal meningitis across all ages through its use in pediatric immunization programs. With the introduction of 13-valent PCV (PCV13) we can expect to see a reduction in the incidence of pneumococcal meningitis due to the six additional serotypes included, as well as continued protection against pneumococcal meningitis due to PCV7 serotypes. Robust surveillance systems are essential for the evaluation of the impact of PCV13 on all-type pneumococcal meningitis and for monitoring the evolution of non-vaccine serotype pneumococcal meningitis.

Eradication of invasive pneumococcal disease due to the seven-valent pneumococcal conjugate vaccine serotypes in Calgary, Alberta

BACKGROUND

The seven-valent pneumococcal conjugate vaccine (PCV7) was licensed in Canada in 2001. Routine infant vaccination programs in Alberta began in 2002. Several years after PCV7 introduction, the routine use of PCV7 in infants and high-risk children has led to near elimination of invasive pneumococcal disease (IPD) caused by vaccine serotypes.

METHODS

Prospective, population-based surveillance of all IPD cases was conducted from January 1998 to December 2010. Demographic, clinical and microbiologic data were collected.

RESULTS

There were 1462 IPD cases over 13 years. Comparing PCV7 serotype IPD incidence in the prevaccine period (1998-2001) to the late postvaccine period (2007-2010), there were declines in children 0-5 months (100%), 6-23 months (98%), 2-4 years (97%), 5-15 years (100%) as well as in adults 16-64 years (73%), 65-84 years (90%) and ≥85 years of age (100%). From 2008 to 2010, there were no cases of PCV7 serotype IPD in children under 2 years of age. There have been increases in non-PCV7 serotype IPD; notably, serotypes 5 and 19A have increased significantly in adults and 19A in children.

CONCLUSIONS

PCV7 serotype IPD has been eliminated in vaccine-eligible young children and nearly eliminated in all other age groups. Serotype 19A increased significantly at all ages before the introduction of an expanded valency pneumococcal conjugate vaccine.

Prevalence of Streptococcus pneumoniae serotypes causing invasive and non-invasive disease in South East Asia: a review

BACKGROUND

Streptococcus pneumoniae is a major cause of bacterial infections resulting in significant morbidity and mortality worldwide. Currently, up to 13 serotypes are included in pneumococcal conjugate vaccines (PCVs). However, the serotype formulation of these vaccines was initially designed to protect children against serotypes most commonly causing invasive disease in North America, and may not reflect the serotype distribution across the world. Data regarding pneumococcal epidemiology from the other parts of the world, in particular South East Asia, has not been reviewed.

METHODS

This systematic literature review analyses published serotype data regarding S. pneumoniae isolates from South East Asian countries (defined as countries belonging to the Association of South East Asian Nations, ASEAN): Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand and Vietnam up to 3rd of March 2012.

RESULTS

Analysis of data from six ASEAN countries, from which information on pneumococcal serotypes was available, showed that the most common disease causing serotypes (in rank order) were 19F, 23F, 14, 6B, 1, 19A and 3. Serotype distribution of pneumococcal isolates was similar across the ASEAN region. Serotype level data was more commonly reported for pneumococcal isolates causing invasive pneumococcal disease than for those from non-invasive disease. Studies from Malaysia, Thailand and Singapore contributed the largest proportion of pneumococcal isolates, and serotype data, when compared to other ASEAN countries.

CONCLUSION

This review demonstrates that the majority of IPD causing serotypes in SE Asia are included in currently licensed PCVs. However, PCV's are included in the routine childhood immunisation schedule of only one of the ten countries included in this analysis. Our findings demonstrate the scarcity of information available on serotype prevalence and distribution of pneumococci in SE Asia.

Serotype replacement in disease after pneumococcal vaccination

Vaccination with heptavalent pneumococcal conjugate vaccine (PCV7) has significantly reduced the burden of pneumococcal disease and has had an important public health benefit. Because this vaccine targets only seven of the more than 92 pneumococcal serotypes, concerns have been raised that non-vaccine serotypes (NVTs) could increase in prevalence and reduce the benefits of vaccination. Indeed, among asymptomatic carriers, the prevalence of NVTs has increased substantially, and consequently, there has been little or no net change in the bacterial carriage prevalence. In many populations, pneumococcal disease caused by NVT has increased, but in most cases this increase has been less than the increase in NVT carriage. We review the evidence for serotype replacement in carriage and disease, and address the surveillance biases that might affect these findings. We then discuss possible reasons for the discrepancy between near-complete replacement in carriage and partial replacement for disease, including differences in invasiveness between vaccine serotypes. We contend that the magnitude of serotype replacement in disease can be attributed, in part, to a combination of lower invasiveness of the replacing serotypes, biases in the pre-vaccine carriage data (unmasking), and biases in the disease surveillance systems that could underestimate the true amount of replacement. We conclude by discussing the future potential for serotype replacement in disease and the need for continuing surveillance.

Meningococcal factor H binding proteins in epidemic strains from Africa: implications for vaccine development

BACKGROUND

Factor H binding protein (fHbp) is an important antigen for vaccines against meningococcal serogroup B disease. The protein binds human factor H (fH), which enables the bacteria to resist serum bactericidal activity. Little is known about the vaccine-potential of fHbp for control of meningococcal epidemics in Africa, which typically are caused by non-group B strains.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated genes encoding fHbp in 106 serogroup A, W-135 and X case isolates from 17 African countries. We determined complement-mediated bactericidal activity of antisera from mice immunized with recombinant fHbp vaccines, or a prototype native outer membrane vesicle (NOMV) vaccine from a serogroup B mutant strain with over-expressed fHbp. Eighty-six of the isolates (81%) had one of four prevalent fHbp sequence variants, ID 4/5 (serogroup A isolates), 9 (W-135), or 74 (X) in variant group 1, or ID 22/23 (W-135) in variant group 2. More than one-third of serogroup A isolates and two-thirds of W-135 isolates tested had low fHbp expression while all X isolates tested had intermediate or high expression. Antisera to the recombinant fHbp vaccines were generally bactericidal only against isolates with fHbp sequence variants that closely matched the respective vaccine ID. Low fHbp expression also contributed to resistance to anti-fHbp bactericidal activity. In contrast to the recombinant vaccines, the NOMV fHbp ID 1 vaccine elicited broad anti-fHbp bactericidal activity, and the antibodies had greater ability to inhibit binding of fH to fHbp than antibodies elicited by the control recombinant fHbp ID 1 vaccine.

CONCLUSION/SIGNIFICANCE

NOMV vaccines from mutants with increased fHbp expression elicit an antibody repertoire with greater bactericidal activity than recombinant fHbp vaccines. NOMV vaccines are promising for prevention of meningococcal disease in Africa and could be used to supplement coverage conferred by a serogroup A polysaccharide-protein conjugate vaccine recently introduced in some sub-Saharan countries.

Cost-effectiveness of conjugate pneumococcal vaccination in Singapore: comparing estimates for 7-valent, 10-valent, and 13-valent vaccines

INTRODUCTION

Although multiple studies of cost-effectiveness of pneumococcal conjugate vaccines have been conducted, no such study has examined Singapore's situation nor compared the licensed conjugate vaccines in an Asian population. This paper estimates the costs and public health impacts of pneumococcal conjugate vaccine programs, varying estimates of serotype replacement and herd immunity effects as key parameters in the analysis. Based in part on a 2008 analysis also presented here, Singapore has approved the PCV-7, PHiD-10, and PCV-13 pneumococcal conjugate vaccines as part of its National Childhood Immunisation Programme.

METHODS

An economic evaluation was performed using a Markov simulation model populated with Singapore-specific population parameters, vaccine costs, treatment costs, and disease incidence data. The vaccinated infant and child cohort of 226,000 was 6% of the Singapore resident population of 3.8 million. Vaccine efficacy estimates were constructed for PCV-7, PHiD-10, and PCV-13 vaccines based on their serotype coverage in Singapore and compared to 'no vaccination'. The model estimated impacts over a five-year time horizon with 3% per year discounting of costs and health effects. Costs were presented in 2010 U.S. dollars (USD) and Singapore dollars (SGD). Sensitivity analyses included varying herd immunity, serotype replacement rates, vaccine cost, and efficacy against acute otitis media.

RESULTS

Under base case assumptions for the revised analysis (i.e., herd effects in the unvaccinated population equivalent to 20% of direct effects) PCV-13 prevented 834 cases and 7 deaths due to pneumonia, meningitis, and bacteremia in the vaccinated population, and 952 cases and 191 deaths in the unvaccinated population over the 5-year time horizon. Including herd effects, the cost-effectiveness ratio for PCV-13 was USD $37,644 (SGD $51,854) per QALY. Without herd effects, however, the ratio was USD $204,535 (SGD $281,743) per QALY. The PCV-7 cost per QALY including herd effects was USD $43,275 (SGD $59,610) and for PHiD-10 the ratios were USD $45,100 (SGD $62,125). The original 2008 analysis, which had higher estimates of pneumonia prevention due to herd immunity and lower estimates of cost per dose, had found a cost-effectiveness ratio of USD $5562 (SGD $7661) per QALY for PCV-7.

CONCLUSIONS

When compared to cost-effectiveness thresholds recommended by the World Health Organization (WHO), our 2008 analysis found that vaccination of infants in Singapore with PCV-7 was very cost-effective if herd immunity effects were present. However, knowledge on herd immunity and serotype replacement that emerged subsequent to this analysis changed our expectations about indirect effects. Given these changed inputs, our current estimates of infant vaccination against pneumococcal disease in Singapore find such programs to be moderately cost-effective compared to WHO thresholds. The different findings from the 2008 and 2011 analyses suggest that the dynamic issue of serotype replacement should be monitored post-licensure and, as changes occur, vaccine effectiveness and cost-effectiveness analyses should be re-evaluated.

A decade-long surveillance of nasopharyngeal colonisation with Streptococcus pneumoniae among children attending day-care centres in south-eastern France: 1999-2008

The antimicrobial resistance and serotype distribution of Streptococcus pneumoniae (SP) among children attending day-care centres in south-eastern France were monitored from 1999 to 2008, before and after interventions promoting prudent antibiotic use initiated in 2000 and the availability of pneumococcal conjugate vaccine in 2003. Antibiotic susceptibility and serotypes of SP isolates were determined on nasopharyngeal samples of children aged 3-40 months attending day-care centres, from January to March 1999, 2002, 2004, 2006 and 2008. SP carriage fell from 54% to 45%, and SP with diminished susceptibility to penicillin (PDSP) fell from 34% to 19%. Antibiotic prescriptions dropped from 63% to 38% of children, but third-generation cephalosporins were increasingly prescribed. The overall antibiotic susceptibility increased. Over 90% of the children had received at least one vaccine dose in 2008. Vaccine serotypes 6B, 9V, 19F and 23F (76%) in 1999 were replaced by non-vaccine types (95%) in 2008, among which were 15 (20%), 19A (15%), 23A/B (10%) and 6A (9%). Serotypes 6A, 19A and 15 accounted for over 50% of PDSP strains in 2008 versus 6% in 1999. Children now mostly harbour non-vaccine types; however, PDSP isolates are mainly recruited among these. Vaccine-related benefits may be threatened by combined vaccine- and antibiotic-driven selective pressure.