Effect of pneumococcal conjugate vaccine on pneumococcal meningitis

Contribution of vaccines to our understanding of pneumococcal disease

Pneumonia is the leading cause of mortality in children in developing countries and is also the leading infectious cause of death in adults. The most important cause of pneumonia is the Gram-positive bacterial pathogen, Streptococcus pneumoniae, also known as the pneumococcus. It has thus become the leading vaccine-preventable cause of death and is a successful and diverse human pathogen. The development of conjugate pneumococcal vaccines has made possible the prevention of pneumococcal disease in infants, but has also elucidated aspects of pneumococcal biology in a number of ways. Use of the vaccine as a probe has increased our understanding of the burden of pneumococcal disease in children globally. Vaccination has also elucidated the clinical spectrum of vaccine-preventable pneumococcal infections; the identification of a biological niche for multiple pneumococcal serotypes in carriage and the differential invasiveness of pneumococcal serotypes; the impact of pneumococcal transmission among children on disease burden in adults; the role of carriage as a precursor to pneumonia; the plasticity of a naturally transformable pathogen to respond to selective pressure through capsular switching and the accumulation of antibiotic-resistance determinants; and the role of pneumococcal infections in hospitalization and mortality associated with respiratory viral infections, including both seasonal and pandemic influenza. Finally, there has been a recent demonstration that pneumococcal pneumonia in children may be an important cause of hospitalization for those with underlying tuberculosis.

Pharmacoeconomic assessment of implementing a universal PCV-13 vaccination programme in the Valencian public health system (Spain)

BACKGROUND

Heptavalent pneumococcal conjugate vaccine (PCV-7) was licensed to provide immunity against pneumococcal disease caused by seven serotypes of S. pneumoniae. Thirteen-valent pneumococcal conjugate vaccine (PCV-13) includes 6 additional serotypes for preventing invasive pneumococcal disease.

OBJECTIVE

The objective of this study was to estimate the potential health benefits, costs, and cost-effectiveness of vaccination with PCV-13 in the Community of Valencia and to generate valuable information for policy makers at regional and country levels.

METHODS

A decision tree was designed to determine the health and economic outcomes in hypothetical cohorts of vaccinated and unvaccinated children followed over their lifetime. Information about disease incidence and serotype distribution were gathered from local databases and from published and unpublished local records. PCV-13 effectiveness was extrapolated from PCV-7 efficacy data. A 5% of herd effect and a serotype replacement of 25% were considered for the base case scenario. Only direct costs were taken into account and results were expressed in terms of life-years gained (LYG) and quality adjusted life years (QALY).

RESULTS

Implementing a universal PCV-13 vaccination program in the Community of Valencia would decrease the number of hospital admitted pneumonia to less than 4571 cases while avoiding 310 cases of IPD and 82,596 cases of AOM throughout the cohort lifetime. A total of 190 S. pneumoniae related deaths would be averted over the same period. Total medical costs of non-vaccinating the cohort of newborns would reach up to 403,850.859€ compared to 438,762.712€ that would represent vaccinating the cohort. The incremental cost of vaccinating the children was estimated in 12,794€/LYG and 10,407€/QALY, respectively.

CONCLUSIONS

A universal PCV-13 vaccination program in the Community of Valencia would be a cost-effective intervention from the payer perspective after preventing for pneumococcal infections and for decreasing its associated mortality and morbidity.

Bacterial causes of empyema in children, Australia, 2007-2009

An increase in the incidence of empyema worldwide could be related to invasive pneumococcal disease caused by emergent nonvaccine replacement serotypes. To determine bacterial pathogens and pneumococcal serotypes that cause empyema in children in Australia, we conducted a 2-year study of 174 children with empyema. Blood and pleural fluid samples were cultured, and pleural fluid was tested by PCR. Thirty-two (21.0%) of 152 blood and 53 (33.1%) of 160 pleural fluid cultures were positive for bacteria; Streptococcus pneumoniae was the most common organism identified. PCR identified S. pneumoniae in 74 (51.7%) and other bacteria in 19 (13.1%) of 145 pleural fluid specimens. Of 53 samples in which S. pneumoniae serotypes were identified, 2 (3.8%) had vaccine-related and 51 (96.2%) had nonvaccine serotypes; 19A (n = 20; 36.4%), 3 (n = 18; 32.7%), and 1 (n = 8; 14.5%) were the most common. High proportions of nonvaccine serotypes suggest the need to broaden vaccine coverage.

Impact of universal pneumococcal vaccination on hospitalizations for pneumonia and meningitis in children in Montevideo, Uruguay

BACKGROUND

In March 2008, Uruguay included PCV7 into the routine vaccination program, in a 2 + 1 schedule for children <2 years of age. Catch-up immunization was offered to children born in 2007. Greater than 95% of children received their first and second doses. The aim of this study was to assess the effect of this strategy.

METHODS

Annual hospitalization rates (per 10,000 discharges) for community-acquired pneumonia (CAP) in children <14 years of age and pneumococcal meningitis are described prior to PCV7 vaccination (2005-2007), during the year of implementation (2008) and following vaccine introduction (2009). Data regarding age, diagnosis, vaccination status, and pneumococcal serotype were obtained from Hospital Pereira Rossell databases and vaccination records.

RESULTS

Comparison of hospitalization rates for CAP and pneumococcal-CAP (P-CAP) between prevaccine years (2005-2007) and the year after vaccination (2009) decreased significantly in all children by 56% and 48.2%, respectively. Significant reduction was observed for vaccine serotype P-CAP (serotype 14 P-CAP decreased from 26.6 to 2.5 per 10,000 discharges) in children <2 years of age. A significant reduction in pneumococcal meningitis of 59% was seen in this age group; median rates prevaccination decreased from 17 (12.2-24.9) to 7 (3-11.8) after the administration of vaccine. No vaccine failures for P-CAP or pneumococcal meningitis were seen in fully immunized children.

CONCLUSIONS

One year after PCV7 introduction into the routine vaccination schedule of Uruguay, there was a rapid and significant reduction in rates of CAP, P-CAP, and pneumococcal meningitis in children <2 years of age.

Vaccine discovery and translation of new vaccine technology

An unprecedented increase in new vaccine development has occurred over the past three decades. This activity has resulted in vaccines that protect against an increased range of vaccine-preventable diseases, vaccines that reduce the number of required injections, and vaccines with improved safety and purity. New methods of discovery, such as reverse vaccinology, structural biology, and systems biology, promise new vaccines for different diseases and efficient development pathways for these vaccines. We expect development of vaccines not only for infectious diseases in children but also for healthy adults, pregnant women, and elderly people, and for new indications such as autoimmune disease and cancer. We have witnessed a concomitant development of new technology for assessment of vaccine safety to rapidly identify potential safety issues. Success of these new approaches will depend on effective implementation of vaccination programmes, creative thinking on the part of manufacturers and regulators as to how best to ensure that safe and effective vaccines are available in a timely manner, and improvement of public awareness about the benefits and risks of new vaccines in a way that encourages confidence in vaccines.

Heterogeneity of the efficacy of the 23-valent pneumococcal polysaccharide vaccine caused by various underlying conditions of chronic pulmonary disease in older patients: prospective cohort study

OBJECTIVE

To determine the ideal conditions for use of the 23-valent pneumococcal polysaccharide vaccine (PPV23) in older outpatients with chronic pulmonary diseases.

DESIGN

Prospective cohort study.

PARTICIPANTS

1378 outpatients with chronic pulmonary diseases ≥ 60 years of age.

INTERVENTION

Participants were educated about PPV23, and those who responded affirmatively were vaccinated between August and November 2002. The participants who chose no intervention served as controls. The prevaccine period was defined as August 2001 to August 2002. Participants were followed for 2 years from December 2002 or until death.

MAIN OUTCOME MEASURES

Events of interest included the first episode of bacterial (including pneumococcal) pulmonary infection (primary endpoint) and death of any cause (secondary endpoint).

RESULTS

Frequent episodes of pulmonary infection during the prevaccine period significantly decreased event-free survival during the 2-year observation period (p<0.001). Chronic respiratory failure was associated with a decreased event-free survival only when the pulmonary infection episode did not occur in the prevaccine period (p<0.001). No significant differences in event-free survival were observed between the vaccinated and unvaccinated group during analysis of the entire cohort. In the Cox proportional hazards regression model, event-free survival decreased significantly when pulmonary infection occurred in the prevaccine period. In the subgroup analysis, the first episode of bacterial pulmonary infection (but not death of any cause) was reduced significantly by PPV23 only in patients with chronic respiratory failure who had no episodes of pulmonary infection during the prevaccine period (p=0.019).

CONCLUSION

The efficacy of PPV23 against pulmonary infection and death of any cause might be unachievable if pulmonary infection occurs during the prevaccine period. PPV23 needs to be given to older patients with chronic pulmonary disease at an earlier time in which infectious complications in the lung have not yet occurred.

Treatment of Drug-resistant Pneumococcal Meningitis

The approach to therapy in patients with pneumococcal meningitis has changed considerably over the past 20 years. Given the emergence of pneumococcal strains that are intermediately susceptible or highly resistant to penicillin, penicillin is not recommended as empiric therapy for presumed pneumococcal meningitis; the combination of vancomycin and a third-generation cephalosporin (either cefotaxime or ceftriaxone) should be used, pending isolation of the organism and in vitro susceptibility testing. For patients with pneumococcal meningitis caused by highly penicillin- or cephalosporin-resistant strains, the addition of rifampin can be considered if the organism is susceptible in vitro, the expected clinical or bacteriologic response is delayed, or the pneumococcal isolate has a cefotaxime or ceftriaxone minimal inhibitory concentration greater than 4 μg/mL. Meropenem is not a good option for monotherapy of highly penicillin- or cephalosporin-resistant strains, but use of a fluoroquinolone with in vitro activity against Streptococcus pneumoniae (specifically moxifloxacin) is an option in patients failing standard therapy; if used, however, it should be combined with a third-generation cephalosporin or vancomycin. Newer glycopeptides, daptomycin, and linezolid require further study to determine their efficacy in patients with pneumococcal meningitis.

Pathophysiology and treatment of bacterial meningitis

Bacterial meningitis is a medical emergency requiring immediate diagnosis and immediate treatment. Streptococcus pneumoniae and Neisseria meningitidis are the most common and most aggressive pathogens of meningitis. Emerging antibiotic resistance is an upcoming challenge. Clinical and experimental studies have established a more detailed understanding of the mechanisms resulting in brain damage, sequelae and neuropsychological deficits. We summarize the current pathophysiological concept of acute bacterial meningitis and present current treatment strategies.

Incorporation of real-time PCR into routine public health surveillance of culture negative bacterial meningitis in São Paulo, Brazil

Real-time (RT)-PCR increases diagnostic yield for bacterial meningitis and is ideal for incorporation into routine surveillance in a developing country. We validated a multiplex RT-PCR assay for Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae in Brazil. Risk factors for being culture-negative, RT-PCR positive were determined. The sensitivity of RT-PCR in cerebrospinal fluid (CSF) was 100% (95% confidence limits, 96.0%-100%) for N. meningitidis, 97.8% (85.5%-99.9%) for S. pneumoniae, and 66.7% (9.4%-99.2%) for H. influenzae. Specificity ranged from 98.9% to 100%. Addition of RT-PCR to routine microbiologic methods increased the yield for detection of S. pneumoniae, N. meningitidis, and H. influenzae cases by 52%, 85%, and 20%, respectively. The main risk factor for being culture negative and RT-PCR positive was presence of antibiotic in CSF (odds ratio 12.2, 95% CI 5.9-25.0). RT-PCR using CSF was highly sensitive and specific and substantially added to measures of meningitis disease burden when incorporated into routine public health surveillance in Brazil.

Pneumonia and poverty: a prospective population-based study among children in Brazil

BACKGROUND

Children in developing country suffer the highest burden of pneumonia. However, few studies have evaluated associations between poverty and pneumonia.

METHODS

A prospective population-based study on pneumonia was carried out as part of the Latin America Epidemiological Assessment of Pneumococcus (LEAP study). Chest x-rays were obtained for children one to 35 months old with suspected pneumonia presenting to emergency care centers and hospital emergency rooms in Goiania, Brazil. Chest radiographs were evaluated according to WHO guidelines. Clustering of radiologically-confirmed pneumonia were evaluated using a Poisson-based spatial scan statistic. Associations between census socioeconomic indicators and pneumonia incidence rates were analyzed using generalized linear models.

RESULTS

From May, 2007 to May, 2009, chest radiographs were obtained from 11 521 children with clinical pneumonia; 3955 episodes were classified as radiologically-confirmed. Incidence rates were significantly higher in very low income areas (4825.2 per 105) compared to high income areas (1637.3 per 105). Spatial analysis identified clustering of confirmed pneumonia in Western (RR 1.78; p=0.001) and Southeast (RR 1.46; p=0.001) regions of the city, and clustering of hospitalized pneumonia in the Western region (RR 1.69; p=0.001). Lower income households and illiteracy were associated with pneumonia incidence.

CONCLUSIONS

In infants the risk of developing pneumonia is inversely associated with the head of household income and with the woman educational level. Areas with deprived socioeconomic conditions had higher incidence of pneumonia and should be targeted for high vaccination coverage.

Bacterial meningitis in the United States, 1998-2007

BACKGROUND

The rate of bacterial meningitis declined by 55% in the United States in the early 1990s, when the Haemophilus influenzae type b (Hib) conjugate vaccine for infants was introduced. More recent prevention measures such as the pneumococcal conjugate vaccine and universal screening of pregnant women for group B streptococcus (GBS) have further changed the epidemiology of bacterial meningitis.

METHODS

We analyzed data on cases of bacterial meningitis reported among residents in eight surveillance areas of the Emerging Infections Programs Network, consisting of approximately 17.4 million persons, during 1998-2007. We defined bacterial meningitis as the presence of H. influenzae, Streptococcus pneumoniae, GBS, Listeria monocytogenes, or Neisseria meningitidis in cerebrospinal fluid or other normally sterile site in association with a clinical diagnosis of meningitis.

RESULTS

We identified 3188 patients with bacterial meningitis; of 3155 patients for whom outcome data were available, 466 (14.8%) died. The incidence of meningitis changed by -31% (95% confidence interval [CI], -33 to -29) during the surveillance period, from 2.00 cases per 100,000 population (95% CI, 1.85 to 2.15) in 1998-1999 to 1.38 cases per 100,000 population (95% CI 1.27 to 1.50) in 2006-2007. The median age of patients increased from 30.3 years in 1998-1999 to 41.9 years in 2006-2007 (P<0.001 by the Wilcoxon rank-sum test). The case fatality rate did not change significantly: it was 15.7% in 1998-1999 and 14.3% in 2006-2007 (P=0.50). Of the 1670 cases reported during 2003-2007, S. pneumoniae was the predominant infective species (58.0%), followed by GBS (18.1%), N. meningitidis (13.9%), H. influenzae (6.7%), and L. monocytogenes (3.4%). An estimated 4100 cases and 500 deaths from bacterial meningitis occurred annually in the United States during 2003-2007.

CONCLUSIONS

The rates of bacterial meningitis have decreased since 1998, but the disease still often results in death. With the success of pneumococcal and Hib conjugate vaccines in reducing the risk of meningitis among young children, the burden of bacterial meningitis is now borne more by older adults. (Funded by the Emerging Infections Programs, Centers for Disease Control and Prevention.).

Streptococcus pneumoniae serotype 6C: an intra- and interclonal complex comparison

We report the annotated draft genome sequences of four serotype 6C Streptococcus pneumoniae isolates of differing genetic backgrounds. Serotype 6C isolates are increasing in prevalence and becoming progressively more resistant to antibiotics. As a result, these strains are likely to become more important in the near future.

Next generation pneumococcal vaccines

Currently licensed pneumococcal vaccines are based on the generation of antibodies to the pneumococcal polysaccharide, of which there are more than 90 different types. While these vaccines are highly effective against the serotypes included, their high cost and limited serotype coverage limit their usefulness worldwide, particularly in low resource areas. Thus alternative or adjunctive options are being actively pursued. This review will present these various approaches, including variations of the polysaccharide-protein conjugate strategy, protein-based strategies, and whole cell pneumococcal vaccines. The immunological basis for these different approaches is discussed as well.

Streptococcus pneumoniae clonal complex 199: genetic diversity and tissue-specific virulence

Streptococcus pneumoniae is an important cause of otitis media and invasive disease. Since introduction of the heptavalent pneumococcal conjugate vaccine, there has been an increase in replacement disease due to serotype 19A clonal complex (CC)199 isolates. The goals of this study were to 1) describe genetic diversity among nineteen CC199 isolates from carriage, middle ear, blood, and cerebrospinal fluid, 2) compare CC199 19A (n = 3) and 15B/C (n = 2) isolates in the chinchilla model for pneumococcal disease, and 3) identify accessory genes associated with tissue-specific disease among a larger collection of S. pneumoniae isolates. CC199 isolates were analyzed by comparative genome hybridization. One hundred and twenty-seven genes were variably present. The CC199 phylogeny split into two main clades, one comprised predominantly of carriage isolates and another of disease isolates. Ability to colonize and cause disease did not differ by serotype in the chinchilla model. However, isolates from the disease clade were associated with faster time to bacteremia compared to carriage clade isolates. One 19A isolate exhibited hypervirulence. Twelve tissue-specific genes/regions were identified by correspondence analysis. After screening a diverse collection of 326 isolates, spr0282 was associated with carriage. Four genes/regions, SP0163, SP0463, SPN05002 and RD8a were associated with middle ear isolates. SPN05002 also associated with blood and CSF, while RD8a associated with blood isolates. The hypervirulent isolate's genome was sequenced using the Solexa paired-end sequencing platform and compared to that of a reference serotype 19A isolate, revealing the presence of a novel 20 kb region with sequence similarity to bacteriophage genes. Genetic factors other than serotype may modulate virulence potential in CC199. These studies have implications for the long-term effectiveness of conjugate vaccines. Ideally, future vaccines would target common proteins to effectively reduce carriage and disease in the vaccinated population.

Molecular analysis improves pathogen identification and epidemiologic study of pediatric parapneumonic empyema

BACKGROUND

Parapneumonic empyema (PPE) is an increasingly common complication of bacterial pneumonia. Epidemiologic study is complicated by the low frequency of positive cultures. We sought to describe the epidemiology of PPE in children using molecular analysis of pleural fluid.

METHODS

We performed molecular testing for bacterial pathogens using archived pleural fluid from children hospitalized in 2009 with PPE. Real-time polymerase chain reaction (PCR) to detect Streptococcus pneumoniae, Staphylococcus aureus (including methicillin-resistant), Streptococcus pyogenes, Haemophilus influenzae, and Mycoplasma pneumoniae as well as PCR-based serotyping of S. pneumoniae was performed. Demographic, laboratory, and microbiologic data were abstracted.

RESULTS

Pleural fluid specimens from 63 children were available for PCR. By culture, a pathogen was isolated from blood and/or pleural fluid in 22 (35%) patients, with S. pneumoniae in 15 (24%), S. pyogenes in 3 (5%), and methicillin-resistant Staphylococcus aureus in 4 (6%). By PCR, a pathogen was detected in 53 (84%), including S. pneumoniae in 45 (71%). Compared with culture, PCR testing significantly increased detection of any pathogen (35% vs. 84%; P < 0.001) and of S. pneumoniae (24% vs. 71%; P < 0.001). Serotype 7F was the most common pneumococcal serotype detected. Comparison of culture-negative to culture-positive disease showed differences in both the pathogen profile and clinical outcomes.

CONCLUSIONS

Molecular analysis of pleural fluid more than doubled the detection of pathogens causing PPE. S. pneumoniae was the most common cause of both culture-positive and culture-negative PPE, although serotype distribution and outcomes differed.

Global prevailing and emerging pediatric pneumococcal serotypes

Streptococcus pneumoniae is the leading cause of vaccine-preventable deaths among children younger than 5 years of age worldwide. The 7-valent pneumococcal conjugate vaccine (PCV7) is currently licensed in more than 90 countries and has contributed to significant declines in the incidence of invasive pneumococcal disease (IPD). Recent studies report an increased incidence of IPD caused by non-PCV7 vaccine serotypes (NVTs). Seroepidemiology of IPD caused by NVTs following the introduction of PCV7 is of interest, and this article provides a comprehensive global summary of the prevailing and emerging serotypes causing IPD in children. Currently, globally emerging or persistent NVTs include serotypes 1, 3, 5, 6A, 7F and 19A. Serotypes included in the recently licensed 10-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PCV10) and 13-valent pneumococcal conjugate vaccine (PCV13) account for pneumococcal disease burdens in most developed countries of 65-85% and 80-90%, respectively. The seroprevalence of NVTs after widespread use of PCV10 and PCV13 requires ongoing monitoring.

[Nasopharyngeal carriage, antibiotic susceptibility and serotyping of Streptococcus pneumoniae and Haemophilus influenzae in children attending day care centers]

The aim of this study was to investigate the nasal carriage of Streptococcus pneumoniae (SP) and Haemophilus influenzae (HI) in children.

METHODS

Nasal samples were swabbed from children 3 months to 3 years of age, between December 2006 and April 2007, in 10 day-care centers in Dijon.

RESULTS

Three hundred and eighty-five children, 22.7 ± 8.4 months, were included. All were vaccinated against H1 and 92% had received at least one dose of PCV7 vaccine. HI colonization (55%) was associated with young age and concomitant pneumococcal carriage (52.4% vs. 39%). Amoxicillin/clavulanate and cefotaxime resistance rates were 17% and 0.5%. Pneumococcal carriage (48%) was increased in case of prior hospitalization. The rate of PDSP, 50%, was increased in case of recent infection (91% vs. 81%), previous antibiotherapy (64% vs. 41%), and decreased if PCV7 was completed (40.2% vs. 61,8%). There was no resistance to amoxicillin. The erythromycin resistance rate was 50.5%. 15% of the strains were vaccinal serotypes. Thirty-six and 41% of the strains were related and non-related to vaccine serotypes. Twenty-four and 11.6% of the strains were serotypes 19A and 6A respectively.

CONCLUSION

Over the last 10 years the global antibiotic resistance in children decreased for SP (22.9%) but nasal colonization remained stable due to the increase of some serotypes, such as 19A, most often resistant to antibiotics. The vaccine effectiveness against HI is optimal since no HIb serotypes were detected; resistance to betalactam is currently due equally to enzymatic mechanism and alteration of protein binding penicillin.

Nasopharyngeal carriage of individual Streptococcus pneumoniae serotypes during pediatric pneumonia as a means to estimate serotype disease potential

BACKGROUND

We aimed at estimating pneumococcal serotype-specific disease potential in pediatric community-acquired alveolar pneumonia (CAAP), by comparing nasopharyngeal pneumococcal carriage during disease to carriage in healthy children.

METHODS

Pneumococcal nasopharyngeal cultures were obtained from children < 5 years old admitted to the emergency room or hospitalized with radiologically diagnosed CAAP and from healthy controls. Disease potential was estimated by calculating serotype-specific odds ratios (OR) of a given serotype to be carried during disease compared with healthy children (after adjustment for age, ethnicity, previous antibiotic therapy, and season).

RESULTS

A total of 603 and 1504 isolates were obtained from CAAP and healthy children, respectively. A significant OR > 1.0 of a specific serotype being carried during disease (suggesting a higher disease potential) was observed with serotypes (by decreasing rank) 1, 5, 22F, 7F, 14, 9V, and 19A. A significant OR < 1.0 of being carried during disease (suggesting a lower disease potential) was observed with serotypes 6A, 6B, 23A, and 35B. Carriage of PCV7 serotypes (grouped) during CAAP was highest in age group 6 to 17 months. PCV10 and PCV13 provided significantly higher coverage for both 6 to 17 and 18 to 35 month age groups.

CONCLUSIONS

It is suggested that serotypes 1, 5, 7F, 9V, 14, 19A, and 22F have a higher disease potential for childhood pneumonia than do serotypes 6A, 6B, 23A, and 35B.

Poor adherence to antibiotic prescribing guidelines in acute otitis media--obstacles, implications, and possible solutions

Many countries now have guidelines on the clinical management of acute otitis media. In almost all, the public health goal of containing acquired resistance in bacteria through reduced antibiotic prescribing is the main aim and basis for recommendations. Despite some partial short-term successes, clinical activity databases and opinion surveys suggest that such restrictive guidelines are not followed closely, so this aim is not achieved. Radical new solutions are needed to tackle irrationalities in healthcare systems which set the short-term physician-patient relationship against long-term public health. Resolving this opposition will require comprehensive policy appraisal and co-ordinated actions at many levels, not just dissemination of evidence and promotion of guidelines. The inappropriate clinical rationales that underpin non-compliance with guidelines can be questioned by evidence, but also need specific developments promoting alternative solutions, within a framework of whole-system thinking. Promising developments would be (a) physician training modules on age-appropriate analgesia and on detection plus referral of rare complications like mastoiditis, and (b) vaccination against the most common and serious bacterial pathogens.

From vaccine practice to vaccine science: the contribution of human immunology to the prevention of infectious disease

Over the past 50 years, the practice of vaccination has reached the important goal of reducing many of the diseases that afflicted humanity in past centuries. A better understanding of immunological mechanisms underlying the induction of immune protection and the advent of new technology led to improved vaccine preparations based on purified microbial antigens and new adjuvants able to boost both humoral and cellular immune responses. Despite these tremendous advances, much remains to be done. The emergence of new pathogens, the spread of strains resistant to antibiotics and the enormous increase in latent infections are urgently demanding more and more effective vaccines. Understanding the immunological mechanisms that mediate resistance against infections would certainly provide valuable information for the design of new candidate vaccines.

PneumococcaL meningitis in french children before and after the introduction of pneumococcal conjugate vaccine

In France, despite a high rate of pneumococcal conjugate vaccine coverage, the number of cases of pneumococcal meningitis in children did not decline significantly between 2001–2002 (n = 264) and 2007–2008 (n = 244). A decline was observed among children < 2 years old (185 [70.1%] to 134 [54.9%] cases; P = 0.0004), but was counterbalanced by an increase among children ≥ 2 years old (79 [29.9%] to 110 [45.1%] cases). Mean age increased significantly, from 2.3 (median 0.8) to 3.8 (median 1.5) years. After pneumococcal conjugate vaccine 7 implementation, a wide diversity of serotypes implicated in pneumococcalmeningitis was observed; serotypes 19A and 7F were the most frequent.

The impact of vaccination on rhinosinusitis and otitis media

Routine childhood vaccination has affected frequency and bacteriology of acute otitis media (AOM) and acute bacterial rhinosinusitis (ABRS). Routine influenza vaccination moderately reduces AOM, and the Haemophilus influenzae type b vaccine likely had a minor role in AOM and ABRS. The conjugated pneumococcal vaccine has drastically reduced invasive pneumococcal disease and caused a moderate decrease in AOM and, likely, ABRS. The vaccine serotypes of Streptococcus pneumoniae have been all but eliminated, but other serotypes have emerged as potential causes of invasive disease. Antibiotic resistance in pneumococcal disease seems to have decreased. A decrease in the overall prevalence of S. pneumoniae may have resulted in an increased incidence of Staphylococcus aureus as a pathogen in AOM and ABRS due to the concept of bacterial interference.

Pneumococcal polysaccharide conjugate vaccine (13-valent, adsorbed) [prevenar 13®]

The pneumococcal polysaccharide conjugate vaccine Prevenar 13® (PCV13) comprises 13 capsular Streptococcus pneumoniae polysaccharide serotypes that are individually conjugated to nontoxic diphtheria protein (cross-reactive material [CRM(197)]). In randomized, comparator-controlled, phase III trials in healthy infants aged 2-6 months, PCV13 elicited a strong immune response against all 13 pneumococcal serotypes in terms of the proportion of vaccinees achieving reference antibody levels with a two- or three-dose primary vaccination series. Immune responses for the seven serotypes common to PCV13 and the 7-valent pneumococcal conjugate vaccine Prevenar® (PCV7) were generally similar. Antibodies to all vaccine serotypes were functional. A booster dose of PCV13 administered between 11 and 15 months of age generally boosted the immune response against all 13 serotypes, regardless of whether infants had previously received PCV13 or PCV7 during the primary vaccination phase. Robust immune responses against all serotypes were achieved when PCV13 was administered as catch-up vaccination schedules in older infants and young children aged 7-72 months. Importantly, PCV13 did not interfere with the immune responses to coadministered routine paediatric vaccines. Based on data for PCV7, it is expected that PCV13 will also display protective efficacy against invasive pneumococcal disease, otitis media and pneumonia. PCV13 was generally well tolerated, with an adverse event profile similar to that of PCV7 after any vaccine dose.

Streptococcus pneumoniae meningitis in Alberta pre- and postintroduction of the 7-valent pneumococcal conjugate vaccine

OBJECTIVE

To describe the epidemiology, clinical characteristics, microbiology and outcomes of patients of all ages with Streptococcus pneumoniae meningitis two years pre- and postintroduction of a S pneumoniae 7-valent conjugate vaccine program in Alberta in children <2 years of age.

METHODS

Between 2000 and 2004, all cases of invasive pneumococcal disease in Alberta were identified. From this cohort, patients with S pneumoniae meningitis were identified by chart review. Clinical data, laboratory data and in-hospital outcomes were collected.

RESULTS

Of the 1768 cases of invasive pneumococcal disease identified between 2000 and 2004, 110 (6.2%) had S pneumoniae meningitis. The overall incidence was 0.7 per 100,000 persons and remained unchanged over the study period. The rate in children <2 years of age appeared to fall over time, from 10.5 per 100,000 persons in 2000 to five per 100,000 persons in 2004, although there was insufficient evidence of a statistically significant time trend within any age group. Overall, the mean age was 30 years and 47% were male. In-hospital mortality was 20%, ranging from 6% in those ≤2 years of age to 31% for those ≥18 years of age, despite appropriate antimicrobial therapy.

CONCLUSION

The high mortality rate associated with S pneumoniae meningitis suggests that prevention by vaccination is critical. In children <2 years of age, there was a downward trend in the rate of S pneumoniae meningitis after implementation of the S pneumoniae 7-valent conjugate vaccine program, but rates were still high.

Bacterial meningitis

Bacterial meningitis is a neurological emergency. Empiric antimicrobial and adjunctive therapy should be initiated as soon as a single set of blood cultures has been obtained. Clinical signs suggestive of bacterial meningitis include fever, headache, meningismus, vomiting, photophobia, and an altered level of consciousness. The peripheral white blood cell count with a left shift, an elevated serum procalcitonin and C-reactive protein, and a cerebrospinal fluid pleocytosis with a predominance of polymorphonuclear leukocytes, and a decreased glucose concentration are predictive of bacterial meningitis. Patients with documented bacterial meningitis and those in whom the diagnosis is a strong possibility should be admitted to the intensive care unit. Timely recognition of bacterial meningitis and initiation of therapy are critical to outcome.

Parental decline of pneumococcal vaccination and risk of pneumococcal related disease in children

BACKGROUND

An increasing number of parents are choosing to decline immunizations for their children. This study examined the association between the parental decision to decline pneumococcal conjugate (PCV7) vaccinations and the risk of hospitalization due to pneumococcal disease or lobar pneumonia in children.

METHODS

We conducted a case-control study nested within a cohort of children enrolled in the Kaiser Permanente Colorado (KPCO) health plan between 2004 and 2009. Each child hospitalized with pneumococcal disease or lobar pneumonia (n=106) was matched to 4 randomly selected controls (n=401). Cases were matched to controls by age, sex, high-risk status, calendar time, and length of enrollment in KPCO. Disease status and parental vaccination decisions were validated with medical record review. Cases and controls were classified as vaccine decliners or vaccine acceptors.

RESULTS

Among 106 cases, there were 6 (6%) PCV7 vaccine decliners; among 401 controls, there were 4 (1%) vaccine decliners. Children of parents who declined PCV7 immunization were 6.5 times (OR=6.5; 95% CI=1.7, 24.5) more likely to be hospitalized for invasive pneumococcal disease or lobar pneumonia than vaccinated children.

CONCLUSIONS

Parental decline of pneumococcal vaccination apparently increases the risk for hospitalization due to pneumococcal disease or lobar pneumonia in children. Providers can use this information when helping parents weigh the benefits and risks of immunizing their children.

Invasive pneumococcal disease after implementation of a reduced three-dose pneumococcal conjugate vaccine program: a pediatric tertiary care center experience

Following the implementation of a government-sponsored reduced three-dose (2 + 1) heptavalent conjugate pneumococcal vaccine (PCV7) program, we report a 61.4% decrease in the number of cases of invasive pneumococcal diseases (IPD) treated at our institution. Four years after the implementation of the three-dose reduced vaccine program, only 7.4% of IPD were caused by PCV7 serotypes, and there was an increase in the proportion of IPD caused by nonPCV7 serotypes; serotype 19A represented 40.7% of the strains isolated during the last year of the study. These results, similar to those previously observed with a regular four-dose (3 + 1) PCV7 schedule, are reassuring as to the effectiveness of a reduced three-dose (2 + 1) PCV7 program. Increasing numbers of IPD caused by nonPCV7 serotypes warrant the use of a new conjugate pneumococcal vaccine that contains serotype 19A.

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

AIM

To determine whether the recent emergence of nonvaccine pneumococcal serotypes has affected the incidence of pneumococcal meningitis in children a few years after the introduction of the heptavalent pneumococcal conjugate vaccine.

METHODS

We conducted a multicentre retrospective cohort study from 2005 to 2008 in all hospitals with paediatric units in northern France. It included all patients < 18 years of age who were admitted for laboratory-confirmed pneumococcal meningitis during the study period. Data were collected from medical files and laboratory records at each hospital and compared with the regional hospital discharge codes. We assessed global and age-specific incidence rates of pneumococcal meningitis from 2005 through 2008, compared them with those from the prevaccine era (2000-2002) and evaluated pneumococcal serotypes.

RESULTS

In all, 41 cases were found during the study period. The incidence rate of pneumococcal meningitis varied from 0.8/100,000 children < 18 years in 2005 to 1.8/100,000 children in 2008 (2.2-fold increase, p = 0.06); and from 1.8 to 11.9/100,000 children < 2 years (6.5-fold increase, p = 0.004). This increase was caused by nonvaccine pneumococcal serotypes.

CONCLUSION

The incidence of pneumococcal meningitis in infants has rebounded in northern France during the pneumococcal conjugate vaccine programme, with the emergence of nonvaccine pneumococcal serotypes.

Pertussis in Florida, 2000-2006: trends in a historically low-incidence state

OBJECTIVE

Florida, the fourth most populous state in the nation, has had historically low incidence rates of pertussis, the only vaccine-preventable disease with increasing numbers of reported cases. We compared the epidemiology and incidence rates of pertussis in Florida with other states and the United States.

METHODS

We used Florida and federal surveillance data from 2000 through 2006.

RESULTS

Reported incidence of pertussis in Florida, numbers of cases, and proportions of adolescents and adults all increased during the seven-year study period. Florida incidence rates increased from 0.44 to 1.28, but the state's incidence was always ranked 45th or lower among the states. Reported pertussis cases and those among adolescents and adults in Florida increased during the study period. Ten counties, containing 60% of Florida's population, reported two-thirds of the state's cases.

CONCLUSIONS

Pertussis reported from Florida mirrored national trends with increasing incidence, numbers of cases, and proportions of adolescent and adult cases. Despite the increases, Florida maintained its historic pattern of pertussis incidence rates that are consistently lower than national figures. Limited laboratory diagnostics and a focus on the pediatric population likely contributed to the lower rates of pertussis in Florida. More emphasis on surveillance of adolescent and adult cases is needed.

Dengue vaccine trial guidelines and role of large-scale, post proof-of-concept demonstration projects in bringing a dengue vaccine to use in dengue endemic areas

In this review, we consider the issues impacting conduct and design of dengue vaccine trials with reference to the recently published World Health Organization "Guidelines for Conduct of Clinical Trials of Dengue Vaccines in Endemic Areas." We discuss logistic, scientific and ethical challenges concerning evaluation and introduction of dengue vaccines; these range from randomized trials that establish "proof of concept" of vaccine efficacy, to post-"proof of concept" trials, particularly demonstration projects likely to be required for licensure or for the introduction of an already licensed vaccine into public use. We clarify and define the meaning of "proof of concept" in the clinical trial context and the meaning of terms "phase 2b", "phase 3b" and "demonstration project", which are commonly used but have not been defined well in the clinical literature.

Public health and economic impact of the 13-valent pneumococcal conjugate vaccine (PCV13) in the United States

The 7-valent pneumococcal conjugate vaccine (PCV7) has dramatically decreased pneumococcal disease incidence, and the 13-valent vaccine (PCV13) protects against 6 additional Streptococcus pneumoniae serotypes. A decision-analytic model was constructed to evaluate the impact of infant vaccination with PCV13 versus PCV7 on pneumococcal disease incidence and mortality as well as the incremental benefit of a serotype catch-up program. PCV13 effectiveness was extrapolated from observed PCV7 data, using assumptions regarding serotype prevalence and PCV13 protection against additional serotypes. The model predicts that PCV13 is more effective and cost saving compared with PCV7, preventing 106,000 invasive pneumococcal disease (IPD) cases and 2.9 million pneumonia cases, and saving $11.6 billion over a 10-year period. The serotype catch-up program would prevent an additional 12,600 IPD cases and 404,000 pneumonia cases, and save an additional $737 million compared with no catch-up program.