Invasive pneumococcal disease among infants before and after introduction of pneumococcal conjugate vaccine

Risk of invasive pneumococcal disease varies by neighbourhood characteristics: implications for prevention policies

This study investigates neighbourhood variation in rates of pneumococcal bacteraemia and community-level factors associated with neighbourhood heterogeneity in disease risk. We analysed data from 1416 adult and paediatric cases of pneumococcal bacteraemia collected during 2005-2008 from a population-based hospital surveillance network in metropolitan Philadelphia. Cases were geocoded using residential address to measure disease incidence by neighbourhood and identify potential neighbourhood-level risk factors. Overall incidence of pneumococcal bacteraemia was 36∙8 cases/100,000 population and varied significantly (0-67∙8 cases/100,000 population) in 281 neighbourhoods. Increased disease incidence was associated with higher population density [incidence rate ratio (IRR) 1∙10/10,000 people per mile², 95% confidence interval (CI) 1∙0-1∙19], higher percent black population (per 10% increase) (IRR 1∙07, 95% CI 1∙04-1∙09), population aged ≤5 years (IRR 3∙49, CI 1∙8-5∙18) and population aged ≥65 years (IRR 1∙19, CI 1∙00-1∙38). After adjusting for these characteristics, there was no significant difference in neighbourhood disease rates. This study demonstrates substantial small-area variation in pneumococcal bacteraemia risk that appears to be explained by neighbourhood sociodemographic characteristics. Identifying neighbourhoods with increased disease risk may provide valuable information to optimize implementation of prevention strategies.

Pediatric invasive pneumococcal disease in the United States in the era of pneumococcal conjugate vaccines

Invasive infections caused by Streptococcus pneumoniae continue to be a major cause of morbidity and mortality worldwide, especially in children under 5 years of age. In the United States, 90% of invasive pneumococcal infections in children are caused by 13 serotypes of S. pneumoniae. The licensure (in 2000) and subsequent widespread use of a heptavalent pneumococcal conjugate vaccine (PCV7) have had a significant impact on decreasing the incidence of serious invasive pneumococcal disease (IPD) in all age groups, especially in children under 2 years of age. However, the emergence of replacement non-PCV7 serotypes, especially serotype 19A, has resulted in an increase in the incidence of serious and invasive infections. In 2010, a 13-valent PCV was licensed in the United States. However, the impact that this vaccine will have on IPD remains to be seen. The objectives of this review are to discuss the epidemiology of serious and invasive pneumococcal infections in the United States in the PCV era and to review some of the pneumococcal vaccines that are in development.

[Hospital costs related to streptococcal meningitis among children in São José dos Campos, São Paulo State, Brazil]

Knowledge of hospital costs is highly important for public health decision-making. This study aimed to estimate direct hospital costs related to pneumococcal meningitis in children 13 years or younger in the city of São José dos Campos, São Paulo State, Brazil, from January 1999 to December 2008. Data were obtained from medical records. Hospital costs were calculated according to the mixed method for measurement of quantities of items with identified costs and value attribution to items consumed (micro-costing and gross-costing). All costs were calculated according to monetary values for November 2009 and in Brazilian currency (Real). Epi Info 3.5.1 was used for frequencies and means analysis. Forty-one cases were reported. Direct hospital costs varied from R$ 1,277.90 to R$ 19,887.56 (mean = R$ 5,666.43), or 10 to 20 times the mean cost of hospitalization for other diseases. Hospital staff labor was the highest cost, followed by medication, procedures, supplies, and lab tests.

Evaluation of serotype-specific immunity to Streptococcus pneumoniae in pregnant women and cord blood of infants: impact of race and ethnicity

BACKGROUND

Although invasive pneumococcal disease (IPD) has significantly decreased in children since the introduction of the pneumococcal conjugate vaccine, instances of IPD from non-PCV7 serotypes have increased. Concerns remain regarding the risk for IPD during the neonatal period. Our objective was to measure quantitative antibody levels to 16 serotypes of Streptococcus pneumoniae in pregnant non-Hispanic black, non-Hispanic white, and Hispanic mothers, and in cord blood samples.

METHODS

Antibody levels were evaluated by Luminex assay.

RESULTS

Forty-two percent of all mothers had protective (-0.35 microg/mL) antibody levels to 16 serotypes. Hispanic mothers were most likely to possess protective antibody levels for 12 serotypes but were less likely to possess protective antibody levels for serotypes 9V, 12F, and 18C, compared to non-Hispanic white or black mothers. Thirty-three percent of cord blood samples demonstrated protective antibody levels. Hispanic infants had a higher prevalence of protective antibodies to all serotypes except 11A, 14, 18C, and 23F. Non-Hispanic black infants had a higher prevalence of protective immunity to serotypes 11A, 14, and 18C, and non-Hispanic white infants to only serotype 23F.

CONCLUSIONS

Hispanic mothers and their infants have a higher prevalence of protective immunity to most serotypes of S pneumoniae, compared to white or black mothers/infants. We found no evidence of a lower prevalence of protective immunity to specific serotypes in non-Hispanic black vs. non-Hispanic white infants that might account for the reported higher incidence of IPDs in blacks. Environmental factors in Hispanic mothers may be responsible for their enhanced level of immunity. A significant number of cord blood samples had inadequate levels of protective immunity to a variety of S pneumoniae serotypes.

Presentation and management of pediatric orbital cellulitis

BACKGROUND

Orbital cellulitis is a serious, vision-threatening infection.

OBJECTIVE

To review the epidemiology and clinical data of pediatric orbital cellulitis in Manitoba.

METHODS

A 12-year retrospective review was conducted of all children (younger than 18 years of age) with orbital cellulitis admitted to Manitoba's only tertiary pediatric centre. Admission rates for orbital cellulitis were compared over three distinct time periods, based on licensure and funding levels of the heptavalent pneumococcal conjugate vaccine (PCV7) in Manitoba.

RESULTS

Thirty-eight patients with orbital cellulitis were identified. Of these, 11% were of Aboriginal ethnicity in contrast with 30% to 40% of children who were admitted for other respiratory illnesses. Subperiosteal abscesses occurred in 31.5%. Only eight patients (21%) required surgery. Follow-up imaging after presentation usually did not indicate a need for subsequent surgical drainage. The mean number of orbital cellulitis cases per 1000 admissions for the following periods - before PCV7 licensure, after licensure and before full provincial funding, and after licensure and full funding - were 0.39, 0.53 and 0.90, respectively. No significant difference was noted among any of the periods as PCV7 coverage increased.

CONCLUSIONS

The rate of subperiosteal abscesses was lower than other reports. This may be due to the median age at presentation. In contrast to admissions for most other respiratory infections at the Winnipeg Children's Hospital (Winnipeg, Manitoba), Aboriginal ethnicity was uncommon. Surprisingly, rates of admissions for orbital cellulitis appeared to show an increasing trend with increasing access to PCV7 in Manitoba, although overall the number of cases was very small. Studies into the changing microbiology of orbital cellulitis and sinusitis are warranted.

Long-term comparative immunogenicity of protein conjugate and free polysaccharide pneumococcal vaccines in chronic obstructive pulmonary disease

BACKGROUND

Although the 23-valent pneumococcal polysaccharide vaccine (PPSV23) protects against invasive disease in young healthy persons, randomized controlled trials in chronic obstructive pulmonary disease (COPD) have demonstrated no benefit in the intention-to-treat population. We previously reported that the 7-valent diphtheria-conjugated pneumococcal polysaccharide vaccine (PCV7) is safe and induced greater serotype-specific immunoglobulin G (IgG) and functional antibody than did PPSV23 1 month after vaccination. We hypothesized that these advantages would persist at 1 and 2 years.

METHODS

One hundred eighty-one patients with moderate to severe COPD were randomized to receive PPSV23 (n = 90) or PCV7 (1.0 mL; n = 91). We measured IgG by enzyme-linked immunosorbent assay and assessed functional antibody activity by a standardized opsonophagocytosis assay, reported as a killing index (OPK). We determined differences in IgG and OPK between vaccine groups at 1 and 2 years.

RESULTS

Relative to PPSV23, PCV7 induced greater OPK at both 1 and 2 years for 6 of 7 serotypes (not 19F). This response was statistically greater for 5 of 7 serotypes at 1 year and 4 of 7 at 2 years. Comparable differences in IgG were observed but were less often statistically significant. Despite meeting Centers for Disease Control and Prevention criteria for PPSV23 administration, almost 50% of individuals had never been vaccinated. No differences in the frequency of acute exacerbations, pneumonia, or hospitalization were observed.

CONCLUSIONS

PCV7 induces a greater functional antibody response than PPSV23 in patients with COPD that persists for 2 years after vaccination. This superior functional response supports testing of conjugate vaccination in studies examining clinical end points.

CLINICAL TRIALS REGISTRATION

NCT00457977.

The impact of new vaccine introduction on immunization and health systems: a review of the published literature

We conducted a systematic review of the published literature to examine the impact of new vaccine introduction on countries' immunization and broader health systems. Six publication databases were searched using 104 vaccine and health system-related search terms. The search yielded 15,795 unique articles dating from December 31, 1911 to September 29, 2010. Based on review of the title and abstract, 654 (4%) of these articles were found to be potentially relevant and were referred for full review. After full review, 130 articles were found to be relevant and included in the analysis. These articles represented vaccines introduced to protect against 10 different diseases (hepatitis A, hepatitis B, Haemophilus influenzae type b disease, human papilloma virus infection, influenza, Japanese encephalitis, meningococcal meningitis, Streptococcus pneumoniae disease, rotavirus diarrhea and typhoid), in various formulations and combinations. Most reviewed articles (97 [75%]) reported experiences in high-income countries. New vaccine introduction was most efficient when the vaccine was introduced into an existing delivery platform and when introduced in combination with a vaccine already in the routine childhood immunization schedule (i.e., as a combination vaccine). New vaccine introduction did not impact coverage of vaccines already included in the routine childhood immunization schedule. The need for increased cold chain capacity was frequently reported. New vaccines facilitated the introduction and widespread use of auto-disable syringes into the immunization and the broader health systems. The importance of training and education for health care workers and social mobilization was frequently noted. There was evidence in high-income countries that new vaccine introduction was associated with reduced health-care costs. Future evaluations of new vaccine introductions should include the systematic and objective assessment of the impacts on a country's immunization system and broader health system, especially in lower-income countries.

Pneumococcal vaccines for children: a global public health priority

Pneumococcal conjugated vaccines have been recommended in children for over a decade in many countries worldwide. Here we review the development of pneumococcal vaccines with a focus on the two types currently available for children and their safety record. We discuss also the effect of vaccines, including the 13-valent pneumococcal conjugate vaccine, on invasive pneumococcal diseases in children, particularly bacteraemia, pneumonia and meningitis, as well as on mucosal disease and carriage. In regions where immunization was implemented in young children, the number of invasive pneumococcal diseases decreased significantly, not only in the target age group, but also in younger and much older subjects. Challenges and future perspectives regarding the development of new 'universal' vaccines, which could bypass the current problem of serotype-specific protection in a context of serotype replacement, are also discussed.

Rates of acquisition and clearance of pneumococcal serotypes in the nasopharynges of children in Kilifi District, Kenya

Background. To understand and model the impact of pneumococcal conjugate vaccines at the population level, we need to know the transmission dynamics of individual pneumococcal serotypes. We estimated serotype-specific clearance and acquisition rates of nasopharyngeal colonization among Kenyan children.

Methods. Children aged 3–59 months who were identified as carriers in a cross-sectional survey were followed-up approximately 1, 2, 4, 8, 16, and 32 days later and monthly thereafter until culture of 2 consecutive swabs yielded an alternative serotype or no pneumococcus. Serotype-specific clearance rates were estimated by exponential regression of interval-censored carriage durations. Duration was estimated as the reciprocal of the clearance rate, and acquisition rates were estimated on the basis of prevalence and duration, assuming an equilibrium state.

Results. Of 2840 children sampled between October 2006 and December 2008, 1868 were carriers. The clearance rate was 0.032 episodes/day (95% confidence interval [CI], .030–.034), for a carriage duration of 31.3 days, and the rate varied by serotype (P < .0005). Carriage durations for the 28 serotypes with ≥10 carriers ranged from 6.7 to 50 days. Clearance rates increased with year of age, adjusted for serotype (hazard ratio, 1.21; 95% CI, 1.15–1.27). The acquisition rate was 0.061 episodes/day (95% CI, .055–.067), which did not vary with age. Serotype-specific acquisition rates varied from 0.0002 to 0.0022 episodes/day. Serotype-specific acquisition rates correlated with prevalence (r = 0.91; P < .00005) and with acquisition rates measured in a separate study involving 1404 newborns in Kilifi (r = 0.87; P < .00005).

Conclusions. The large sample size and short swabbing intervals provide a precise description of the prevalence, duration, and acquisition of carriage of 28 pneumococcal serotypes. In Kilifi, young children experience approximately 8 episodes of carriage per year. The declining prevalence with age is attributable to increasing clearance rates.

Nontypeable pneumococcal isolates among navajo and white mountain apache communities: are these really a cause of invasive disease?

BACKGROUND

Pneumococci could evade pneumococcal conjugate vaccines (PCV) by modifying, mutating, or deleting vaccine-serotype capsule genes or by downregulating capsule production. We sought to assess whether pneumococci that are nontypeable (NT) by the Quellung reaction truly lack capsule genes or are failing to produce capsule in vitro.

METHODS

We applied multilocus sequence typing and a microarray for detection of pneumococcal polysaccharide capsule biosynthesis genes to NT carriage (children aged <5 years; years 1997-2000, 2006-2008) and NT invasive disease (IPD) (all ages; years 1994-2007) isolates from Native American communities.

RESULTS

Twenty-seven of 28 (96.4%) NT IPD isolates had sequence types (STs) typically found among typeable IPD isolates and contained whole or fragments of capsule genes that matched known serotypes; 1 NT-IPD isolate had a profile resembling NT carriage isolates. Forty-nine of 76 (64.5%) NT carriage isolates had STs that typically lack capsule genes and were similar to NT carriage isolates found globally.

CONCLUSIONS

This is the first documentation of IPD from an NT strain confirmed to lack all known capsule genes. Most NT IPD isolates have or had the capacity to produce capsule, whereas a majority of NT carriage isolates lack this capacity. We found no evidence of pneumococcal adaptation to PCV7 via downregulation or deletion of vaccine-serotype capsule genes.

Impact of the emergence of non-vaccine pneumococcal serotypes on the clinical presentation and outcome of adults with invasive pneumococcal pneumonia

The introduction of the 7-valent pneumococcal conjugate vaccine in children has led to a change in the pattern of pneumococcal serotypes causing pneumococcal disease. The aim of this study was to compare the clinical presentation and outcome of invasive pneumococcal pneumonia (IPP) in adults between the pre and post-vaccine era. We have conducted an observational study of all adults hospitalized with IPP, from 1996 to 2001 (pre-vaccine period), and from 2005 to 2009 (post-vaccine period). Incidence, serotype distribution and clinical data were compared between both periods. A total of 653 episodes of IPP were diagnosed. The overall incidence of IPP increased from 14.2 to 17.9 cases per 100 000 population-year (p 0.003). In the post-vaccine period IPP caused by vaccine serotypes decreased (-36%; 95% CI, -52 to -15) while IPP caused by non-vaccine serotypes increased (71%; 95% CI, 41-106). IPP in the post-vaccine period was associated with higher rates of septic shock (19.1% vs. 31.1%, p <0.001). Among patients aged 50-65 years there was a trend towards a greater proportion of case-fatalities (11.6-23.5%, p 0.087). Independent risk factors for septic shock were IPP caused by serotype 3 (OR 2.38; 95% CI, 1.16-4.87) and serotype 19A (OR 6.47, 95% CI, 1.55-27). Serotype 1 was associated with a lower risk of death (OR 0.1; 95% CI, 0.01-0.78). In conclusion, the incidence of IPP in the post-vaccine period has increased in our setting, it is caused mainly by non-vaccine serotypes and it is associated with higher rates of septic shock.

Invasive pneumococcal disease in infants younger than 60 days

OBJECTIVE

To review the epidemiology and clinical course of invasive pneumococcal diseases of infants younger than 60 days.

STUDY DESIGN

All Streptococcus pneumoniae strains isolated from blood and cerebrospinal fluid cultures of infants below the age of 60 days during the years 1999-2009 were included in this study. Demographic, clinical, and laboratory data were collected from medical records.

RESULTS

In all, 24 cases of pneumococcal invasive infections were identified. The primary diagnoses were bacteremia without a focus (n = 13), meningitis (n = 6), bacteremia with otitis media (n = 3), and joint infection with bacteremia (n = 2). Only one of the serotypes found is included in the heptavalent pneumococcal conjugated vaccine (PCV7).

CONCLUSIONS

Streptococcus pneumoniae should be considered and treated empirically in infants with suspected invasive bacterial disease during the first 60 days of life. Routine vaccination with PCV7 in not expected to substantially reduce the incidence of invasive pneumococcal disease in Israeli infants of this age as a result of herd immunity.

Benefits and effectiveness of administering pneumococcal polysaccharide vaccine with seasonal influenza vaccine: an approach for policymakers

For the influenza pandemic of 2009-2010, countries responded to the direct threat of influenza but may have missed opportunities and strategies to limit secondary pneumococcal infections. Delivering both vaccines together can potentially increase pneumococcal polysaccharide vaccine (PPV23) immunization rates and prevent additional hospitalizations and mortality in the elderly and other high-risk groups. We used PubMed to review the literature on the concomitant use of PPV23 with seasonal influenza vaccines. Eight of 9 clinical studies found that a concomitant program conferred clinical benefits. The 2 studies that compared the cost-effectiveness of different strategies found concomitant immunization to be more cost-effective than either vaccine given alone. Policymakers should consider a stepwise strategy to reduce the burden of secondary pneumococcal infections during seasonal and pandemic influenza outbreaks.

Pediatric cochlear implantation: candidacy evaluation, medical and surgical considerations, and expanding criteria

Since the first cochlear implant approved by the US Food and Drug Administration in the early 1980s, great advances have occurred in cochlear implant technology. With these advances, patient selection, preoperative evaluation, and rehabilitation consideration continue to evolve. This article describes the current practice in pediatric candidacy evaluation, reviews the medical and surgical considerations in pediatric cochlear implantation, and explores the expanding criteria for cochlear implantation within the pediatric population.

Pneumococcal carriage and antibiotic resistance in young children before 13-valent conjugate vaccine

BACKGROUND

We sought to measure trends in Streptococcus pneumoniae carriage and antibiotic resistance in young children in Massachusetts communities after widespread adoption of heptavalent 7-valent pneumococcal conjugate vaccine (PCV7) and before the introduction of the 13-valent PCV (PCV13).

METHODS

We conducted a cross-sectional study including collection of questionnaire data and nasopharyngeal specimens among children aged <7 years in primary care practices from 8 Massachusetts communities during the winter season of 2008-2009 and compared with similar studies performed in 2001, 2003-2004, and 2006-2007. Antimicrobial susceptibility testing and serotyping were performed on pneumococcal isolates, and risk factors for colonization in recent seasons (2006-2007 and 2008-2009) were evaluated.

RESULTS

We collected nasopharyngeal specimens from 1011 children, 290 (29%) of whom were colonized with pneumococcus. Non-PCV7 serotypes accounted for 98% of pneumococcal isolates, most commonly 19A (14%), 6C (11%), and 15B/C (11%). In 2008-2009, newly targeted PCV13 serotypes accounted for 20% of carriage isolates and 41% of penicillin-nonsusceptible S. pneumoniae. In multivariate models, younger age, child care, young siblings, and upper respiratory illness remained predictors of pneumococcal carriage, despite near-complete serotype replacement. Only young age and child care were significantly associated with penicillin-nonsusceptible S. pneumoniae carriage.

CONCLUSIONS

Serotype replacement post-PCV7 is essentially complete and has been sustained in young children, with the relatively virulent 19A being the most common serotype. Predictors of carriage remained similar despite serotype replacement. PCV13 may reduce 19A and decrease antibiotic-resistant strains, but monitoring for new serotype replacement is warranted.

Diagnostic value of leukopenia in young febrile infants

We performed a 7-year registry-based retrospective study. We included 1365 infants younger than 3 months of age with fever without a source; 81 (5.9%) had <5000 leukocytes/mm(3). Among the 1021 well-appearing 29- to 90-day-old infants, prevalence of serious bacterial infection (SBI) was 13.8% for those with a normal white blood cell count, 6.8% for those with leukopenia (odds ratio, 0.45), and 36.6% for those with leukocytosis (odds ratio, 3.59). None of the 9 well-appearing febrile neonates with leukopenia developed an SBI. Leukopenia, in well-appearing young febrile infants, should not be considered as an SBI risk factor.

Evolution of the epidemiology of pneumococcal disease among Utah children through the vaccine era

From 1996 to 2009, we analyzed changes in pneumococcal disease (PD) in Utah children aged <18 years using International Classification of Diseases, ninth revision coded hospital discharges. We observed a sustained decrease in the incidence of PD among children <5 years in 2001-2004 (-36%) and 2005-2009 (-34%) compared with 1996-2000 (pre-7-valent pneumococcal conjugate vaccine). Decreases were primarily in bacteremia, uncomplicated pneumonia, and meningitis. In contrast, significant increases in complicated pneumonia/empyema were noted in children <5 years (+95% and +85%) and 5 to 17 years (+2% and +70%). Despite decreases in PD among Utah children, complicated pneumonia/empyema has increased during the 7-valent pneumococcal conjugate vaccine era.

Population structure of hyperinvasive serotype 12F, clonal complex 218 Streptococcus pneumoniae revealed by multilocus boxB sequence typing

At least four outbreaks of invasive disease caused by serotype 12F, clonal complex 218 Streptococcus pneumoniae have occurred in the United States over the past two decades. We studied the population structure of this clonal complex using a sample of 203 outbreak and surveillance isolates that were collected over 22 years from 34 US states and eight other countries. Conventional multilocus sequence typing identified five types and distinguished a single outbreak from the others. To improve typing resolution, multilocus boxB sequence typing (MLBT) was developed from 10 variable boxB minisatellite loci. MLBT identified 86 types and distinguished between each of the four outbreaks. Diversity across boxB loci tended to be positively correlated with repeat array size and, overall, best fit the infinite alleles mutation model. Multilocus linkage disequilibrium was strong, but pairwise disequilibrium decreased with the physical distance between loci and was strongest in one large region of the chromosome, indicating recent recombinations. Two major clusters were identified in the sample, and they were differentiated geographically, as western and more easterly US clusters, and temporally, as clusters that predominated before and after the licensure of pneumococcal conjugate vaccines. The diversity and linkage disequilibrium within these two clusters also differed, suggesting different population dynamics. MLBT revealed hidden aspects of the population structure of these hyperinvasive pneumococci, and it may provide a useful adjunct tool for outbreak investigations, surveillance, and population genetics studies of other pneumococcal clonal complexes.

Pneumococcal conjugate vaccine given shortly after birth stimulates effective antibody concentrations and primes immunological memory for sustained infant protection

Immunization of Kenyan newborns with 7-valent pneumococcal conjugate vaccine is safe and immunogenic. Compared with the Expanded Programme on Immunization schedule beginning at 6 weeks, it stimulates similar antibody concentrations at 18 weeks and induces equal responses to a 9-month booster dose.

Background. In developing countries, newborn immunization with pneumococcal conjugate vaccines (PCVs) could protect young infants who are at high risk of invasive pneumococcal disease (IPD) but might lead to immune tolerance.

Methods. In a randomized trial, young infants received 7-valent PCV at 6, 10, and 14 weeks (Expanded Programme on Immunization [EPI] group) or 0, 10, and 14 weeks (newborn group). Safety was monitored actively at 2–7 days and then passively. Serum samples obtained at birth and 6, 10, 14, 18, 36, and 37 weeks were assayed by enzyme-linked immunosorbent assay for anticapsular immunoglobulin G concentration and avidity. Infants were boosted with either 7-valent PCV or one-fifth dose of pneumococcal polysaccharide vaccine at 36 weeks. Nasopharyngeal swab samples were obtained at 18 and 36 weeks.

Results. Three-hundred neonates and young infants were enrolled. Newborn vaccination was well tolerated. Adverse events occurred equally in each group; none was related to immunization. One infant, immunized at birth, died of unrelated neonatal sepsis. At 18 weeks, protective concentrations (≥0.35 μg/mL) were achieved against each serotype by ≥87% of infants with no significant differences between groups. Geometric mean concentrations were higher in the EPI group for serotypes 4, 9V, 18C, and 19F at 18 weeks and for serotype 4 at 36 weeks. Avidity was greater in the newborn group for serotypes 4, 6B, and 19F at 18 weeks and for serotype 19F at 36 weeks. Booster responses and vaccine-type/nonvaccine-type carriage prevalence did not differ between groups.

Conclusions. PCV was safe, immunogenic, and primed for memory when given at birth. There was no evidence of immune tolerance. Vaccination beginning at birth offers an alternative to control IPD in vulnerable young infants.

Elucidation of structural and antigenic properties of pneumococcal serotype 11A, 11B, 11C, and 11F polysaccharide capsules

Despite the emerging impact of serogroup 11 serotypes in Streptococcus pneumoniae epidemiology, the structures of serogroup 11 capsule types have not been fully elucidated, particularly the locations of O-acetyl substitutions. Here, we report the complete structures of the serotype 11B, 11C, and 11F polysaccharides and a revision to the serotype 11A capsular polysaccharide using nuclear magnetic resonance (NMR). All structures shared a linear, tetrasaccharide backbone with a pendant phosphopolyalcohol. Three of four saccharides are conserved in all serotypes. The individual serotype capsules differed in the identity of one saccharide, the pendant phosphopolyalcohol, and the O-acetylation pattern. Though the assigned locations of O-acetate substitutions in this study differed from those of previous reports, our findings were corroborated with strong correlations to serology and genetics. We examined the binding of serotyping sera to serogroup 11 polysaccharides by using flow cytometry and an inhibition-type enzyme-linked immunosorbent assay (ELISA) and found that de-O-acetylation of capsular polysaccharides by mild hydrolysis decreases its immunoreactivity, supporting the crucial role of O-acetylation in the antigenicity of these polysaccharides. Due to strong correlations between polysaccharide structures and capsule biosynthesis genes, we were able to assign target substrates for the O-acetyltransferases encoded by wcwC, wcwR, wcwT, and wcjE. We identified antigenic determinants for serogroup 11 serotyping sera and highlight the idea that conventional serotyping methods are not capable of recognizing all putative variants of S. pneumoniae serogroup 11.

Overview of the Clinical Consult Case Review of adverse events following immunization: Clinical Immunization Safety Assessment (CISA) network 2004-2009

BACKGROUND

In 2004 the Clinical Consult Case Review (CCCR) working group was formed within the CDC-funded Clinical Immunization Safety Assessment (CISA) Network to review individual cases of adverse events following immunizations (AEFI).

METHODS

Cases were referred by practitioners, health departments, or CDC employees. Vaccine Adverse Event Reporting System (VAERS) searches and literature reviews for similar cases were performed prior to review. After CCCR discussion, AEFI were assessed for a causal relationship with vaccination and recommendations regarding future immunizations were relayed back to the referring physicians. In 2010, surveys were sent to referring physicians to determine the utility and effectiveness of the CCCR service.

RESULTS

CISA investigators reviewed 76 cases during 68 conference calls between April 2004 and December 2009. Almost half of the cases (35/76) were neurological in nature. Similar AEFI for the specific vaccines received were discovered for 63 cases through VAERS searches and for 38 cases through PubMed searches. Causality assessment using the modified WHO criteria resulted in classifying 3 cases as definitely related to vaccine administration, 12 as probably related, 16 as possibly related, 18 as unlikely related, 10 as unrelated, and 17 had insufficient information to assign causality. The physician satisfaction survey was returned by 30 (57.7%) of those surveyed and a majority of respondents (93.3%) felt that the CCCR service was useful.

CONCLUSIONS

The CCCR provides advice about AEFI to practitioners, assigns potential causality, and contributes to an improved understanding of adverse health events following immunizations.

The cost effectiveness of pneumococcal conjugate vaccine in the routine infant immunisation programme of The Gambia

Objectives

To evaluate the cost effectiveness of the use of nine-valent pneumococcal polysaccharide conjugate vaccine in a routine infant immunisation programme based on the Pneumococcal Vaccine Trial (PVT) study in The Gambia.

Methods

This was a clinical trial-based cost-effectiveness study conducted as part of the PVT study. The PVT was an intention-to-treat double-blind placebo-controlled trial of a nine-valent pneumococcal polysaccharide conjugate vaccine. The trial was conducted in the eastern parts of The Gambia, West Africa and recruited 17 437 children aged 40–364 days. A deterministic static cohort model was developed to evaluate direct benefits and costs of pneumococcal conjugate vaccine in The Gambia's routine immunisation programme. The incremental cost-effectiveness ratio (iCER) is defined as vaccinating infants against pneumococcal disease compared with no vaccination from a public provider's perspective using The Gambia's 2005 projected under-one-year population.

Key findings

The results show the use of the vaccine in The Gambia's routine infant vaccination programme to be cost effective using an assumed price of US$5.00 per vial in single-dose vials. Compared with offering no vaccination, the incremental cost per DALYs averted would be 30 DALYs from the public provider perspective. At least 1569 and 340 invasive childhood pneumococcal illnesses and deaths respectively among the cohort would be prevented. In the absence of the vaccine 16 871 DALYs would be lost while with the use of the vaccine 7804 DALYs would be lost. Given the average treatment cost of pneumococcal illnesses to be US$191 (95% confidence interval 180 to 203) the introduction of the vaccine programme would lead to an additional cost of US$274 279 (about US$8.43/child).

Conclusions

The availability of a cost-effective vaccine that can prevent thousands of pneumococcal illnesses and related deaths is a major development towards improving the disease burden in sub-Saharan African countries. This study supports the introduction of nine-valent pneumococcal vaccine into the infant immunisation programme of The Gambia as it is cost effective and will avert many preventable deaths and illnesses. Despite differences in distribution of serotypes between countries, the static model used in the analysis makes the results applicable to other developing countries, particularly those in sub-Saharan Africa.

[Economic evaluation of an infant immunization program in Mexico, based on 13-valent pneumococcal conjugated vaccines]

OBJECTIVES

Vaccination is an effective intervention for reduce child morbidity and mortality associated to pneumococcus. The availability of new anti-pneumococcal vaccines makes it necessary to evaluate its potential impact on public health and costs related to their implementation. The aim of this study was to estimate the cost-effectiveness and cost-utility of immunization strategies based on pneumococcal conjugated vaccines (PCV's) currently available in Mexico from a third payer perspective.

MATERIAL AND METHODS

A decision tree model was developed to assess both, economic and health impact, of anti-pneumococcal vaccination in children <2 years (lifetime time horizon, discount rate: 5% annual). Comparators were: no-vaccination (reference) and strategies based on 7, 10 and 13-valent PCV's. Effectiveness measures were: child deaths avoided, life-years gained (LYG) and quality adjusted life years (QALY's) gained. Effectiveness, utility, local epidemiology and cost of treating pneumococcal diseases were extracted from published sources. Univariate sensitivity analysis were performed.

RESULTS

Immunization dominates no-vaccination: strategy based on 13-valent vaccine prevented 16.205 deaths, gained 331.230 LY's and 332.006 QALY's and saved US$1.307/child vaccinated. Strategies based on 7 and 10-valent PCV's prevented 13.806 and 5.589 deaths, gained 282.193 and 114.251 LY's, 282.969 and 114.972 QALY's and saved US$1.084 and US$731/child vaccinated, respectively. These results were robust to variations in herd immunity and lower immunogenicity of 10-valent vaccine.

CONCLUSIONS

In Mexico, immunization strategies based on 7, 10 and 13-valent PCV's would be cost-saving interventions, however, health outcomes and savings of the strategy based on 13-valent vaccine are greater than those estimated for 7 and 10-valent PCV's.

Invasive pneumococcal disease: association between serotype, clinical presentation and lethality

To ascertain the factors linked to invasive pneumococcal disease (IPD) caused by the different serotypes in the period 2007-2009, following the conjugate vaccine's inclusion in the childhood vaccination schedule, a total of 2013 IPD cases were reviewed. The mean annual incidence in this period was 10.74 cases per 100,000 inhabitans and the lethality was 8.8%. Overall serotype distribution displayed certain peculiarities, such as the high frequency of serotype 5. Serotype 3, male gender, sepsis and presence of risk factors were significantly associated with lethality. Vaccinated children under 5 years of age had a higher risk of disease due to serotype 19A. Serotype 8 was associated with the presence of underlying risk factors.

Emergence of parapneumonic empyema in the USA

BACKGROUND

Although recent reports suggest that the incidence of parapneumonic empyema has increased in several regions of the USA, national trends in disease burden are unknown. National trends in the incidence of parapneumonic empyema hospitalisations and changes in empyema by associated pathogens were examined.

METHODS

National hospitalisation data (1996-2008) were analysed and rates estimated using census estimates as denominators. Incidence rate ratios (IRR) compared 2008 with 1996 rates. Discharge diagnosis codes were used to characterise pathogens associated with empyema hospitalisations.

RESULTS

Overall, national parapneumonic empyema-related hospitalisation rates increased from 3.04 per 100,000 in 1996 to 5.98 per 100,000 in 2008, a 2.0-fold increase (95% CI 1.8 to 2.1). The increases were observed among children (IRR 1.9 (95% CI 1.4 to 2.7)) and adults aged 18-39, 40-64 and ≥65 years (IRR 1.8 (95% CI 1.5 to 2.1), 2.0 (95% CI 1.6 to 3.1) and 1.7 (95% CI 1.5 to 2.0), respectively). Overall, pneumococcal empyema rates remained relatively stable in all age groups whereas streptococcal- (non-pneumococcal) and staphylococcal-related empyema rates increased 1.9-fold and 3.3-fold, respectively, with consistent increases across age groups. The overall in-hospital case fatality ratio for parapneumonic empyema-related hospitalisations was 8.0% (95% CI 6.4% to 9.5%) in 1996 and 7.2% (95% CI 6.3% to 8.1%) in 2008 (p=0.395). Of the empyemas where study pathogens were listed (37.6%), staphylococcal-related empyema had the largest absolute increases across age groups and was associated with longer hospital stay and higher in-hospital mortality than other empyemas.

CONCLUSIONS

Although parapneumonic empyema-related hospitalisations remained relatively rare, they increased substantially during the study period. A number of pathogens, especially staphylococcus, contributed to this increase.

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.

Factors predicting mortality in invasive pneumococcal disease in adults in Alberta

To define the factors associated with 30-day mortality among adult patients with invasive pneumococcal disease (IPD), we conducted a retrospective review of all cases of IPD in Alberta from 2000 to 2004. We hypothesized that multiple factors would be predictive of such mortality. We also examined the factors predictive of early (within 5 days of admission) mortality. We identified 1154 patients who met our inclusion criteria, 163 (14.1%) of whom died within 30 days. Over half (62.6%) of the deaths occurred within 5 days of admission. Ten factors were independently associated with increased 30-day mortality: 3 comorbidity factors-cancer within 5 years of diagnosis of IPD, diabetes, and cirrhosis; 4 complications-requirement for supplemental oxygen, mechanical ventilation, alteration of mental status, and cardiac arrest; 2 microorganism-related factors-infection with high- or infection with intermediate-mortality serotypes; and 1 treatment-related factor-treatment with a single antibiotic. Age 18-40 years and treatment with 2 antibiotics concurrently were associated with lower 30-day mortality. Comorbid illnesses were not contributory to early mortality (within 5 days of admission); instead, complications (alteration of mental status, requirement for supplemental oxygen, mechanical ventilation, and cardiac arrest) as well as infection with high-mortality serotypes and treatment with a single antibiotic were important. Age 18-40 years, infection with serotypes in the polysaccharide vaccine, and treatment with 2 or more than 2 antibiotics were associated with decreased early mortality. Early mortality accounted for 62.6% of the deaths. In conclusion, we found that mortality in IPD is multifactorial, the factors differ for 5- and 30-day mortality, and mortality is associated with host (age and complications), microorganism (pneumococcal serotypes), and therapeutic factors. Our data indicate that treatment with 2 or more antibiotics effective against Streptococcus pneumoniae should be used to treat IPD.

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.

An evaluation of emerging vaccines for childhood pneumococcal pneumonia

BACKGROUND

Pneumonia is the leading cause of child mortality worldwide. Streptococcus pneumoniae (SP) or pneumococcus is estimated to cause 821,000 child deaths each year. It has over 90 serotypes, of which 7 to 13 serotypes are included in current formulations of pneumococcal conjugate vaccines that are efficacious in young children. To further reduce the burden from SP pneumonia, a vaccine is required that could protect children from a greater diversity of serotypes. Two different types of vaccines against pneumococcal pneumonia are currently at varying stages of development: a multivalent pneumococcal conjugate vaccine covering additional SP serotypes; and a conserved common pneumococcal protein antigen (PPA) vaccine offering protection for all serotypes.

METHODS

We used a modified CHNRI methodology for setting priorities in health research investments. This was done in two stages. In Stage I, we systematically reviewed the literature related to emerging SP vaccines relevant to several criteria of interest: answerability; efficacy and effectiveness; cost of development, production and implementation; deliverability, affordability and sustainability; maximum potential for disease burden reduction; acceptability to the end users and health workers; and effect on equity. In Stage II, we conducted an expert opinion exercise by inviting 20 experts (leading basic scientists, international public health researchers, international policy makers and representatives of pharmaceutical companies). The policy makers and industry representatives accepted our invitation on the condition of anonymity, due to sensitive nature of their involvement in such exercises. They answered questions from CHNRI framework and their "collective optimism" towards each criterion was documented on a scale from 0 to 100%.

RESULTS

The experts expressed very high level of optimism (over 80%) that low-cost polysaccharide conjugate SP vaccines would satisfy each of the 9 relevant CHNRI criteria. The median potential effectiveness of conjugate SP vaccines in reduction of overall childhood pneumonia mortality was predicted to be about 25% (interquartile range 20-38%, min. 15%, max 45%). For low cost, cross-protective common protein vaccines for SP the experts expressed concerns over answerability (72%) and the level of development costs (50%), while the scores for all other criteria were over 80%. The median potential effectiveness of common protein vaccines in reduction of overall childhood pneumonia mortality was predicted to be about 30% (interquartile range 26-40%, min. 20%, max 45%).

CONCLUSIONS

Improved SP vaccines are a very promising investment that could substantially contribute to reduction of child mortality world-wide.

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.

Changing epidemiology of invasive pneumococcal disease in Australian children after introduction of a 7-valent pneumococcal conjugate vaccine

OBJECTIVE

To evaluate trends in the incidence and serotype profile of invasive pneumococcal disease (IPD) in Australian children under 2 years of age after the introduction of the 7-valent pneumococcal conjugate vaccine (7vPCV).

DESIGN AND SETTING

Analysis of incidence rates calculated using IPD surveillance data (including age, Indigenous status and serotype of the pneumococcal isolate) from 2002 to 2007 obtained from the National Notifiable Diseases Surveillance System and population estimates obtained from the Australian Bureau of Statistics.

MAIN OUTCOME MEASURES

Trends in IPD incidence among Indigenous and non-Indigenous children between 2002 and 2007; change in the serotype profile of IPD in non-Indigenous children after the introduction of universal 7vPCV vaccination in 2005.

RESULTS

Overall incidence of IPD decreased by 74% in all children < 2 years of age between 2002 and 2007 (P < 0.001). While the incidence of IPD caused by 7vPCV serotypes decreased significantly among both Indigenous and non-Indigenous children, the incidence of non-7vPCV serotype IPD increased significantly in non-Indigenous children (from 9.7 to 15.7 per 100 000, P < 0.001). Compared with a pre-vaccination period (2002-2004), the 2007 incidence of serotype 19A IPD in non-Indigenous children increased significantly (from 2.7 to 8.6 per 100 000, P < 0.001). In 2007, 19A was the predominant serotype causing IPD (37.7%) in all children aged < 2 years.

CONCLUSIONS

The overall incidence of IPD decreased from 2002 to 2007, primarily driven by a reduction in IPD caused by 7vPCV serotypes. However, this was partially offset by a significant increase in the incidence of IPD caused by non-7vPCV serotypes, particularly 19A, in non-Indigenous children.

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.

A second-generation pneumococcal conjugate vaccine for prevention of pneumococcal diseases in children

PURPOSE OF REVIEW

A second-generation 13-valent pneumococcal conjugate vaccine (PCV13) was licensed and recommended for universal immunization of children through age 5 years in 2010. Its introduction is intended to address the residual burden of pneumococcal diseases that persists a decade after the introduction of PCV7.

RECENT FINDINGS

Immunization with PCV7 has resulted in a substantial decline in pneumococcal diseases caused by vaccine serotypes in both vaccinated and unvaccinated persons in the USA. However, an increase in disease due to nonvaccine serotypes, including empyema; the emergence of multidrug, including ceftriaxone, resistant serotype 19A strains; and the need for broader serotype coverage to address the global disease burden provides a rationale for a second-generation conjugate vaccine that includes serotypes 1, 3, 5, 6A, 7F and 19A.

SUMMARY

This article reviews the lessons learned from a decade of experience with PCV7, the increasing problem of disease due to nonvaccine serotypes, and the likelihood of PCV13 to impact the residual disease burden. We contrast the potential differences in prevention of invasive pneumococcal disease compared with nonbacteremic pneumonia and acute otitis media. We conclude with the current recommendations for PCV13 providing a rationale for immunization through age 5 years to create both direct and indirect protection in the population.

Impact of pneumococcal conjugate vaccination of infants on pneumonia and influenza hospitalization and mortality in all age groups in the United States

A seven-valent pneumococcal conjugate vaccine (PCV7) introduced in the United States in 2000 has been shown to reduce invasive pneumococcal disease (IPD) in both vaccinated children and adults through induction of herd immunity. We assessed the impact of infant immunization on pneumococcal pneumonia hospitalizations and mortality in all age groups using Health Care Utilization Project State Inpatient Databases (SID) for 1996 to 2006 from 10 states; SID contain 100% samples of ICD9-coded hospitalization data for the selected states. Compared to a 1996–1997 through 1998–1999 baseline, by the 2005–2006 season, both IPD and pneumococcal pneumonia hospitalizations and deaths had decreased substantially in all age groups, including a 47% (95% confidence interval [CI], 38 to 54%) reduction in nonbacteremic pneumococcal pneumonia (ICD9 code 481 with no codes indicating IPD) in infants <2 years old and a 54% reduction (CI, 53 to 56%) in adults ≥65 years of age. A model developed to calculate the total burden of pneumococcal pneumonia prevented by infant PCV7 vaccination in the United States from 2000 to 2006 estimated a reduction of 788,838 (CI, 695,406 to 875,476) hospitalizations for pneumococcal pneumonia. Ninety percent of the reduction in model-attributed pneumococcal pneumonia hospitalizations occurred through herd immunity among adults 18 years old and older; similar proportions were found in pneumococcal disease mortality prevented by the vaccine. In the first seasons after PCV introduction, when there were substantial state differences in coverage among <5-year-olds, states with greater coverage had significantly fewer influenza-associated pneumonia hospitalizations among children, suggesting that PCV7 use also reduces influenza-attributable pneumonia hospitalizations.

Pneumonia is the world’s leading cause of death in children and the leading infectious cause of death among U.S. adults 65 years old and older. Pneumococcal conjugate vaccination of infants has previously been shown to reduce invasive pneumococcal disease (IPD) among seniors through prevention of pneumococcal transmission from infants to adults (herd immunity). Our analysis documents a significant vaccine-associated reduction not only in IPD but also in pneumococcal pneumonia hospitalizations and inpatient mortality rates among both vaccinated children and unvaccinated adults. We estimate that fully 90% of the reduction in the pneumonia hospitalization burden occurred among adults. Moreover, states that more rapidly introduced their infant pneumococcal immunization programs had greater reductions in influenza-associated pneumonia hospitalization of children, presumably because the vaccine acts to prevent the pneumococcal pneumonia that frequently follows influenza virus infection. Our results indicate that seven-valent pneumococcal conjugate vaccine use has yielded far greater benefits through herd immunity than have previously been recognized.

Well appearing young infants with fever without known source in the emergency department: are lumbar punctures always necessary?

We included 685 consecutive previously healthy well appearing infants younger than 3 months with fever without known source admitted to an Emergency Department without routinely performing lumbar punctures (LP). LP was performed in 198 infants. Of these, 36 (18.1%) showed pleocytosis. Two infants less than 15 days were diagnosed with bacterial meningitis and 47 with aseptic meningitis (6.8%). LP was not performed in 487 infants. Of these, 69 were admitted to ward (46 had urinary tract infection) and 418 were discharged. In this group, we registered 38 unscheduled revisits to the Emergency Department (four aseptic meningitis). All infants did well. It is unnecessary to perform a LP routinely on infants over 1 month of age. The decision to perform the LP in previously healthy and well appearing infants with fever without known source attended by an experienced paediatric emergency physician can be individualized with no subsequent adverse outcomes. This approach may lead to under-diagnosing nonbacterial meningitis.