Epidemiologic features of invasive pneumococcal disease in Belgian children: passive surveillance is not enough

Public health impact and return on investment of Belgium's pediatric immunization program

Objective

We evaluated the public health impact and return on investment of Belgium's pediatric immunization program (PIP) from both healthcare-sector and societal perspectives.

Methods

We developed a decision analytic model for 6 vaccines routinely administered in Belgium for children aged 0-10 years: DTaP-IPV-HepB-Hib, DTaP-IPV, MMR, PCV, rotavirus, and meningococcal type C. We used separate decision trees to model each of the 11 vaccine-preventable pathogens: diphtheria, tetanus, pertussis, poliomyelitis, Haemophilus influenzae type b, measles, mumps, rubella, Streptococcus pneumoniae, rotavirus, and meningococcal type C; hepatitis B was excluded because of surveillance limitations. The 2018 birth cohort was followed over its lifetime. The model projected and compared health outcomes and costs with and without immunization (based on vaccine-era and pre-vaccine era disease incidence estimates, respectively), assuming that observed reductions in disease incidence were fully attributable to vaccination. For the societal perspective, the model included productivity loss costs associated with immunization and disease in addition to direct medical costs. The model estimated discounted cases averted, disease-related deaths averted, life-years gained, quality-adjusted life-years gained, costs (2020 euros), and an overall benefit-cost ratio. Scenario analyses considered alternate assumptions for key model inputs.

Results

Across all 11 pathogens, we estimated that the PIP prevented 226,000 cases of infections and 200 deaths, as well as the loss of 7,000 life-years and 8,000 quality-adjusted life-years over the lifetime of a birth cohort of 118,000 children. The PIP was associated with discounted vaccination costs of €91 million from the healthcare-sector perspective and €122 million from the societal perspective. However, vaccination costs were more than fully offset by disease-related costs averted, with the latter amounting to a discounted €126 million and €390 million from the healthcare-sector and societal perspectives, respectively. As a result, pediatric immunization was associated with overall discounted savings of €35 million and €268 million from the healthcare-sector and societal perspectives, respectively; every €1 invested in childhood immunization resulted in approximately €1.4 in disease-related cost savings to the health system and €3.2 in cost savings from a societal perspective for Belgium's PIP. Estimates of the value of the PIP were most sensitive to changes in input assumptions for disease incidence, productivity losses due to disease-related mortality, and direct medical disease costs.

Conclusion

Belgium's PIP, which previously had not been systematically assessed, provides large-scale prevention of disease-related morbidity and premature mortality, and is associated with net savings to health system and society. Continued investment in the PIP is warranted to sustain its positive public health and financial impact.

Specific antibody deficiency to pneumococcal polysaccharide in a young adult with recurrent respiratory infections: a case report

Specific antibody deficiency against pneumococcal serotypes was detected in a patient with recurrent episodes of fever. A 21-year-old man presented with a two-month history of recurrent episodes of fever and shaking chills. He was diagnosed with recurrent episodes of pneumonia caused by Streptococcus pneumoniae serotype 19A and treated with amoxicillin. Serotype-specific antibodies were not produced against most of the serotypes, which were consistent with moderate specific antibody deficiency. After pneumococcal 13-valent conjugate vaccination and pneumococcal polysaccharide vaccination, he adequately responded to the infecting serotype with an antibody titer of 1.1 µg/mL. There were eventually no recurrent episodes of fever with pneumonia.

Characterization of Streptococcus pneumoniae strains isolated from patients with meningitis before the introduction of pneumococcal conjugate vaccine in Serbia

Introduction: Pneumococcal meningitis is a serious disease which affects mostly children ≤ 2 years, adults ≥ 65 years and immunodeficient patients. The introduction of pneumococcal conjugate vaccine (PCV) into immunization programs worldwide has led to a significant decrease in the incidence of invasive pneumococcal disease, reduction of antibiotic resistance and changes in the distribution of pneumococcal serotypes. In 2018, PCV10 was introduced into the National Immunization Program in Serbia. Aim: The aim of this study was to analyze the serotype distribution and antibiotic susceptibility of pneumococcal strains isolated from meningitis cases in the pre-vaccinal period (2009-2018) in Serbia. Material and methods: Meningeal isolates were sent into the National Reference Laboratory for streptococci between January 2009 and December 2018 for serotyping and antimicrobial susceptibility testing (AST). Serotyping was performed by Quellung reaction, while AST was performed using disk diffusion method and E-test. Results: A total of 199 strains were analyzed and 32 different serotypes have been identified. Among the 55 (27.64%) strains from children ≤16 years, 17 different serotypes were detected of which 19F, 14, 6A, and 6B were the most common. Regarding the 144 (72.36%) adult isolates, 30 different serotypes were present, the most common being 3, 19F, 14, 23F, 6A and 6B. The coverage of pediatric serotypes was 61.82% for PCV10 and 78.18% for PCV13. Statistically significant number of isolates showed resistance to: penicillin (53.26%), erythromycin (45.73%), clindamycin (40.20%), trimethoprim-sulfamethoxazole (34.17%) and tetracycline (34.17%). The isolates from children were more resistant to beta-lactams and macrolides (p < 0.05). Conclusion: During the pre-vaccinal period in Serbia, vaccinal serotypes dominated over non-vaccinal serotypes. Resistance is intermediate to high in the dominant serotypes of children and low in the most common adult serotype 3. Taking into consideration the possible changes in the pneumococcal population in the future, continued monitoring of post-vaccine serotype and resistance trends are essential.

Inhospital death is a biased measure of fatal outcome from bloodstream infection

Purpose

Inhospital death is commonly used as an outcome measure. However, it may be a biased measure of overall fatal outcome. The objective of this study was to evaluate inhospital death as a measure of all-cause 30-day case fatality in patients with bloodstream infection (BSI).

Patients and methods

A population-based surveillance cohort study was conducted, and patients who died in hospital within 30 days (30-day inhospital death) were compared with those who died in any location by day 30 post BSI diagnosis (30-day all-cause case fatality).

Results

A total of 1,773 residents had first incident episodes of BSI. Overall, 299 patients died for a 30-day all-cause case fatality rate of 16.9%. Most (1,587; 89.5%) of the patients were admitted to hospital, and ten (5.4%) of the 186 patients not admitted to hospital died. Of the 1,587 admitted patients, 242 died for a 30-day inhospital death rate of 15.2%. A further 47 patients admitted to hospital died after discharge but within 30 days of BSI diagnosis for a 30-day case fatality rate among admitted patients of 18.2%. Patients who died following discharge within 30 days were older and more likely to have dementia.

Conclusion

The use of inhospital death is a biased measure of true case fatality.

Estimating the prevalence and intensity of Schistosoma mansoni infection among rural communities in Western Tanzania: The influence of sampling strategy and statistical approach

BACKGROUND

Schistosoma mansoni is a parasite of major public health importance in developing countries, where it causes a neglected tropical disease known as intestinal schistosomiasis. However, the distribution of the parasite within many endemic regions is currently unknown, which hinders effective control. The purpose of this study was to characterize the prevalence and intensity of infection of S. mansoni in a remote area of western Tanzania.

METHODOLOGY/PRINCIPAL FINDINGS

Stool samples were collected from 192 children and 147 adults residing in Gombe National Park and four nearby villages. Children were actively sampled in local schools, and adults were sampled passively by voluntary presentation at the local health clinics. The two datasets were therefore analysed separately. Faecal worm egg count (FWEC) data were analysed using negative binomial and zero-inflated negative binomial (ZINB) models with explanatory variables of site, sex, and age. The ZINB models indicated that a substantial proportion of the observed zero FWEC reflected a failure to detect eggs in truly infected individuals, meaning that the estimated true prevalence was much higher than the apparent prevalence as calculated based on the simple proportion of non-zero FWEC. For the passively sampled data from adults, the data were consistent with close to 100% true prevalence of infection. Both the prevalence and intensity of infection differed significantly between sites, but there were no significant associations with sex or age.

CONCLUSIONS/SIGNIFICANCE

Overall, our data suggest a more widespread distribution of S. mansoni in this part of Tanzania than was previously thought. The apparent prevalence estimates substantially under-estimated the true prevalence as determined by the ZINB models, and the two types of sampling strategies also resulted in differing conclusions regarding prevalence of infection. We therefore recommend that future surveillance programmes designed to assess risk factors should use active sampling whenever possible, in order to avoid the self-selection bias associated with passive sampling.

Detection of Rare Antimicrobial Resistance Profiles by Active and Passive Surveillance Approaches

Antimicrobial resistance (AMR) surveillance systems are generally not specifically designed to detect emerging resistances and usually focus primarily on resistance to individual drugs. Evaluating the diversity of resistance, using ecological metrics, allows the assessment of sampling protocols with regard to the detection of rare phenotypes, comprising combinations of resistances. Surveillance data of phenotypic AMR of Canadian poultry Salmonella Heidelberg and swine Salmonella Typhimurium var. 5- were used to contrast active (representative isolates derived from healthy animals) and passive (diagnostic isolates) surveillance and assess their suitability for detecting emerging resistance patterns. Although in both datasets the prevalences of resistance to individual antimicrobials were not significantly different between the two surveillance systems, analysis of the diversity of entire resistance phenotypes demonstrated that passive surveillance of diagnostic isolates detected more unique phenotypes. Whilst the most appropriate surveillance method will depend on the relevant objectives, under the conditions of this study, passive surveillance of diagnostic isolates was more effective for the detection of rare and therefore potentially emerging resistance phenotypes.

Global Burden of Neonatal Invasive Pneumococcal Disease: A Systematic Review and Meta-analysis

BACKGROUND

This study aimed to estimate the global burden of invasive pneumococcal disease (IPD) incidence among neonates during the pre-pneumococcal conjugate vaccine era.

METHODS

A systematic search of published and unpublished data was undertaken. Bias assessment and qualitative synthesis of the included studies were carried out. Random effects models using the method of DerSimonian and Laird were constructed. Subgroup analyses, sensitivity analyses and meta-influence analysis were undertaken. Sources of heterogeneity were investigated.

RESULTS

From 26 neonatal IPD data points in the pre-pneumococcal conjugate vaccine era, the overall pooled neonatal IPD incidence, in the general population, combining all 3 United Nations (UN) country strata was estimated to be 36.0 per 100,000 live births [95% confidence interval (CI): 20.0-64.7 per 100,000]. The pooled neonatal IPD incidence in the general population in the less-developed UN country strata was estimated to be 16.0 per 100,000 live births (95% CI: 3.9-65.6 per 100,000) and in the more-developed stratum was 41.1 per 100,000 live births (95% CI: 29.1-58.1 per 100,000). This counter-intuitive finding is likely to have been affected by data quantity and confounding by time. A pooled estimate for the least-developed stratum was not computable as there was only 1 study in this stratum-a study from The Gambia with an unweighted IPD incidence of 369.5 per 100,000 (95% CI: 119.2-1138.5 per 100,000).

CONCLUSIONS

Pneumococcus was a recognized pathogen among neonates in all development regions of the world. The burden of neonatal IPD, particularly in the least-developed UN country stratum, requires substantial further evaluation.

Severe Infections in HIV-Exposed Uninfected Infants Born in a European Country

Background

Several studies indicate that HIV-exposed uninfected (HEU) children have a high infectious morbidity. We previously reported an increased incidence of group B streptococcus (GBS) infections in HEU infants born in Belgium.

Methods

This study was undertaken to evaluate the incidence and risk factors of all cause severe infections in HEU infants born in Belgium between 1985 and 2006, including the pre-antiretroviral (ARV) prophylaxis era (1985 to 1994). The medical charts of 537 HEU infants followed in a single center were reviewed.

Results

The incidence rate of severe infections during the first year of life was 16.8/100 HEU infant-years. The rates of invasive S. pneumoniae (0.62/100 infant-years) and GBS infections (1.05/100 infant-years) were, respectively, 4 and 13-fold higher in HEU infants than in the general infant population. Preterm birth was a risk factor for severe infections in the neonatal period (aOR = 21.34, 95%CI:7.12–63.93) and post-neonatal period (aHR = 3.00, 95%CI:1.53–5.88). As compared to the pre-ARV prophylaxis era, infants born in the ARV prophylaxis era (i.e., after April 1994) had a greater risk of severe infections (aHR = 2.93; 95%CI:1.07–8.05). This risk excess was present in those who received ARV prophylaxis (aHR 2.01, 95%CI 0.72–5.65) and also in those born in the ARV prophylaxis era who did not benefit from ARV prophylaxis as a result of poor access to antenatal care or lack of compliance (aHR 3.06, 95%CI 0.88–10.66).

Conclusions

In HEU infants born in an industrialized country, preterm birth and being born during the ARV prophylaxis era were risk factors of severe infections throughout the first year of life. These observations have important implications for the clinical management of HIV-infected mothers and their infants.

Epidemiology and outcome of invasive pneumococcal disease among adults in Belgium, 2009-2011

This epidemiological study examined morbidity and case fatality of invasive pneumococcal disease (IPD) in adults in Belgium as well as distribution and antibiotic susceptibility of Streptococcus pneumoniae serotypes.Adults hospitalised with microbiologically proven IPD were prospectively enrolled. The study started in 2009 with patients aged ≥50 years, whereas in 2010 and 2011, patients aged ≥18 years were included. The clinical presentation, patient profile, treatment, outcome, and mortality were recorded during hospitalisation.Outcome was also assessed one month afterdischarge. Of the 1,875 patients with IPD identified, 1,332 were included in the analysis. Bacteraemic pneumonia, affecting 1,049 of the patients, was the most frequent IPD type (79%), and chronic obstructive pulmonary disease and cancer were the main comorbidities.One-third of patients required admission to intensive care unit. A total of 208 (16%) patients died during hospitalisation and an additional 21 (2%) within one month after discharge. Case fatality rates of ≥20%were observed in patients with chronic heart failure, hepatic disease, and renal insufficiency. Serotypes 7F, 1, 19A, and 3 were the most prevalent and together accounted for 47% (569/1,214) of all IPD cases and 42% (80/189) of mortality. Of the patient isolates, 21% (255/1,204) were resistant to erythromycin and 22% (264/1,204) to tetracycline. Penicillin non-susceptibility was mostly found in serotype 19A isolates. These baseline data are essential when assessing the impact of pneumococcal conjugate vaccination in adults in the future.

Pneumococcal aetiology and serotype distribution in paediatric community-acquired pneumonia

Community-acquired pneumonia (CAP) is a major cause of morbidity in children. This study estimated the proportion of children with pneumococcal CAP among children hospitalised with CAP in Belgium and describes the causative serotype distribution after implementation of the 7-valent pneumococcal conjugate vaccine. Children 0–14 years hospitalised with X-ray-confirmed CAP were prospectively enrolled in a multicentre observational study. Acute and convalescent blood samples were collected. Pneumococcal aetiology was assessed by conventional methods (blood or pleural fluid cultures with Quellung reaction capsular typing or polymerase chain reaction [PCR] in pleural fluid), and recently developed methods (real-time PCR in blood and World Health Organization-validated serotype-specific serology). A total of 561 children were enrolled. Pneumococcal aetiology was assessed by conventional methods in 539, serology in 171, and real-time PCR in blood in 154. Pneumococcal aetiology was identified in 12.2% (66/539) of the children by conventional methods alone but in 73.9% by the combination of conventional and recently developed methods. The pneumococcal detection rate adjusted for the whole study population was 61.7%. Serotypes 1 (42.3%), 5 (16.0%), and 7F(7A) (12.8%) were predominant. In conclusion, Streptococcus pneumoniae remains the predominant bacteria in children hospitalised for CAP in Belgium after implementation of 7-valent pneumococcal conjugate vaccine, with non-vaccine-serotypes accounting for the majority of cases. The use of recently developed methods improves diagnosis of pneumococcal aetiology.

Evaluation of a WHO-validated serotype-specific serological assay for the diagnosis of pneumococcal etiology in children with community-acquired pneumonia

BACKGROUND

The etiologic diagnosis of community-acquired pneumonia (CAP) remains challenging in children because blood cultures have low sensitivity. Novel approaches are needed to confirm the role of Streptococcus pneumoniae.

METHODS

In this study, pneumococcal etiology was determined by serology using a subset of blood samples collected during a prospective multicentre observational study of children <15 years of age hospitalized in Belgium with radiogram-confirmed CAP. Blood samples were collected at admission and 3-4 weeks later. Pneumococcal (P)-CAP was defined in the presence of a positive blood or pleural fluid culture. Serotyping of S. pneumoniae isolates was done with the Quellung reaction. Serological diagnosis was assessed for 9 serotypes using World Health Organization-validated IgG and IgA serotype-specific enzyme-linked immunosorbent assays (ELISAs).

RESULTS

Paired admission/convalescent sera from 163 children were evaluated by ELISA (35 with proven P-CAP and 128 with nonproven P-CAP). ELISA detected pneumococci in 82.8% of patients with proven P-CAP. The serotypes identified were the same as with the Quellung reaction in 82% and 59% of cases by IgG ELISA and IgA ELISA, respectively. Overall, ELISA identified a pneumococcal etiology in 55% of patients with nonproven P-CAP. Serotypes 1 (51.6%), 7F (19%) and 5 (15.7%) were the most frequent according to IgG ELISA.

CONCLUSIONS

In conclusion, the serological assay allows recognition of pneumococcal origin in 55% of CAP patients with negative culture. This assay should improve the diagnosis of P-CAP in children and could be a useful tool for future epidemiological studies on childhood CAP etiology.

Antibiotic therapy for pediatric community-acquired pneumonia: do we know when, what and for how long to treat?

Community-acquired pneumonia (CAP) is a common cause of morbidity among children in developed countries and accounts for an incidence of 10-40 cases per 1000 children in the first 5 years of life. Given the clinical, social and economic importance of CAP, there is general agreement that prompt and adequate therapy is essential to reduce the impact of the disease. The aim of this discussion paper is to consider critically the available data concerning the treatment of uncomplicated pediatric CAP and to consider when, how and for how long it should be treated. This review has identified the various reasons that make it difficult to establish a rational approach to the treatment of pediatric CAP, including the definition of CAP, the absence of a pediatric CAP severity score, the difficulty of identifying the etiology, limited pharmacokinetic (PK)/pharmacodynamic (PD) studies, the high resistance of the most frequent respiratory pathogens to the most widely used anti-infectious agents and the lack of information concerning the changes in CAP epidemiology following the introduction of new vaccines against respiratory pathogens. More research is clearly required in various areas, such as the etiology of CAP and the reasons for its complications, the better definition of first- and second-line antibiotic therapies (including the doses and duration of parenteral and oral antibiotic treatment), the role of antiviral treatment and on how to follow-up patients with CAP. Finally, further efforts are needed to increase vaccination coverage against respiratory pathogens and to conduct prospective studies of their impact.

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.

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.

Impact of conjugate 7-valent vaccination in Belgium: addressing methodological challenges

In Belgium, the 7-valent pneumococcal conjugate vaccine (PCV7) was introduced into the national schedule in 2007. The early impact of PCV7 vaccination on paediatric invasive disease was estimated by comparing pre- and post-vaccination incidence from national surveillance. In children <2 year-olds, vaccine-serotype incidence declined by 96% but non-vaccine-types increased 2-3-fold. Overall invasive disease decreased by 23-46%, depending on adjustment for under-reporting and pre-vaccine trends. Non-vaccine-types 1 and 19A had increased before PCV7 use, suggesting the contribution of other factors. Estimation of PCV7 impact comparing pre- and post-vaccination data should adjust for pre-vaccine trends, and serotype dynamics need further exploration.

Epidemiology of Haemophilus influenzae bacteremia: a multi-national population-based assessment

OBJECTIVES

Haemophilus influenzae is an important cause of invasive infection but contemporary data in non-selected populations is limited.

METHODS

Population-based surveillance for Haemophilus influenzae bacteremia was conducted in seven regions in Australia, Canada, and Denmark during 2000-2008.

RESULTS

The overall annual incidence rate was 1.31 per 100,000 population and type specific rates were 0.08 for H. influenzae serotype b (Hib), 0.22 for H. influenzae serotypes a, c-f (Hiac-f), and 0.98 per 100,000 for non-typeable H. influenzae (NTHi). Very young and old patients were at highest risk. The serotypes causing disease varied according to age with nearly all cases in the elderly due to NTHi. The presence of comorbid medical illness was common with 14%, 16%, and 29% patients having Charlson comorbidity scores of 1, 2, and ≥ 3, respectively. The 30-day all-cause case-fatality rate was 18%. Factors independently associated with death at 30-days in logistic regression analysis included male gender, hospital-onset disease, older age, and lower respiratory tract, central nervous system, or unknown focus of infection.

CONCLUSIONS

Haemophilus influenzae is an important cause of morbidity and mortality particularly with NTHi in the elderly. These data serve as a baseline to assess the future effectiveness of new preventative interventions.

Pneumococcal serotypes in children in 4 European countries

After heptavalent pneumococcal conjugate vaccine (PCV7) was marketed in France, Spain, Belgium, and England and Wales (United Kingdom), invasive disease from non-PCV7 serotypes (NVT) increased. Adjusted serotype-specific incidences among children <15 years of age were compared between 1999-2002 (prevaccine) and 2005-2006 (postmarketing). Vaccine coverage increased to approximately 32%-48% in France, Spain, and Belgium but remained <1% in England and Wales. Serotype 1 incidence rose in all age groups and countries (incidence rate ratio [IRR] 1.3-4.2; p<0.004), independently of PCV7 use, but incidence of serotypes 7F and 19A increased most in France, Spain, and Belgium (IRR 1.9-16.9 in children <5 years; p<0.001), where PCV7 coverage was greater. Vaccine-induced replacement of PCV7 serotypes possibly contributed to NVT increases, as did secular trends. New vaccines targeting these serotypes are available, but serotype dynamics needs further exploration that accounts for underreporting and prevaccine trends.

The dynamics of nasopharyngeal streptococcus pneumoniae carriage among rural Gambian mother-infant pairs

Background

Streptococcus pneumoniae is an important cause of community acquired pneumonia, sepsis, meningitis and otitis media globally and has been incriminated as a major cause of serious childhood bacterial infections in The Gambia. Better understanding of the dynamics of transmission and carriage will inform control strategies.

Methods

This study was conducted among 196 mother-infant pairs recruited at birth from six villages in the West Kiang region of The Gambia. Nasopharyngeal swabs were collected from mother-infant pairs at birth (within 12 hours of delivery), 2, 5 and 12 months. Standard techniques of culture were used to identify carriage and serotype S. pneumoniae.

Results

Of 46 serotypes identified, the 6 most common, 6A, 6B, 14, 15, 19F and 23F, accounted for 67.3% of the isolates from infants. Carriage of any serotype among infants rose from 1.5% at birth to plateau at approximately 80% by 2 m (prevalence at 2 m = 77%; 5 m = 86%; 12 m = 78%). Likewise, maternal carriage almost doubled in the first 2 months post-partum and remained elevated for the next 10 m (prevalence at birth = 13%; 2 m = 24%; 5 m = 22%; 12 m = 21%). Carriage was significantly seasonal in both infants and mothers with a peak in December and lowest transmission in August. The total number of different serotypes we isolated from each infant varied and less than would be expected had the serotypes assorted independently. In contrast, this variability was much as expected among mothers. The half-life of a serotype colony was estimated to be 1.90 m (CI_95%: 1.66-2.21) in infants and 0.75 m (CI_95%: 0.55-1.19) in mothers. While the odds for a serotype to be isolated from an infant increased by 9-fold if it had also been isolated from the mother, the population attributable fraction (PAF) of pneumococcal carriage in infants due to maternal carriage was only 9.5%. Some marked differences in dynamics were observed between vaccine and non-vaccine serotypes.

Conclusions

Colonisation of the nasopharynx in Gambian infants by S. pneumoniae is rapid and highly dynamic. Immunity or inter-serotype competition may play a role in the dynamics. Reducing mother-infant transmission would have a minimal effect on infant carriage.

Surveillance for antimicrobial resistant organisms: potential sources and magnitude of bias

Surveillance has been recognized as a fundamental component in the control of antimicrobial- resistant infections. Although surveillance data have been widely published and utilized by researchers and decision makers, little attention has been paid to assessment of their validity. We conducted this review in order to identify and explore potential types and magnitude of bias that may influence the validity or interpretation of surveillance data. Six main potential areas were assessed. These included bias related to use of inadequate or inappropriate (1) denominator data, (2) case definitions, and (3) case ascertainment; (4) sampling bias; (5) failure to deal with multiple occurrences, and (6) those related to laboratory practice and procedures. The magnitude of these biases varied considerably for the above areas within different study populations. There are a number of potential biases that should be considered in the methodological design and interpretation of antimicrobial-resistant organism surveillance.

National paediatric immunization program of high risk groups: no effect on the incidence of invasive pneumococcal diseases

This study monitors the epidemiology of invasive pneumococcal diseases (IPD) in hospitalized children up to 60 months of age before (February 2001-October 2004) and after (November 2004-January 2007) the introduction of a national risk group immunization program with "Prevenar" in Austria. The IPD incidence rates, per 100,000, for IPD were 7.6 before and 6.4 after the risk group immunization program, while there was a significant reduction (p<0.05) for meningitis, 3.1 before and 1.6 after. Overall, the most commonly observed serotypes were 14 (34.2%), 6B (11.7%), and 23F (6.7%). 71.7% of the identified strains were vaccine types; 12.5% were vaccine-related serotypes. No clinically relevant changes in the incidence rate of IPDs or shift/replacement of serotypes was documented. Antimicrobial resistance predominated against erythromycin (32.5%) and clarithromycin (26.7%). Our data show that this risk group vaccination program had no impact on the incidence of IPD in young children.

Serotypes and pathogens in paediatric pneumonia

Multiple pathogens may cause pneumonia. Three vaccines with demonstrated or potentially major impact on paediatric pneumonia caused by pneumococcus and/or non-typable Haemophilus influenzae (NTHi) are projected to soon become globally available. Estimating the magnitude of this impact requires precise knowledge of the etiology of pneumonia. We reviewed studies to evaluate the relative importance of specific pneumococcal serotypes and NTHi as pneumonia pathogens. While emerging conjugate vaccines, especially those containing serotype 1, appear to have great potential toward the prevention of childhood pneumonia based on expanded serotype coverage, the importance of NTHi in childhood pneumonia has yet to be elucidated.

Incidence of invasive pneumococcal disease in the Czech Republic and serotype coverage by vaccines, 1997-2006

We studied the incidence of invasive pneumococcal disease (IPD) in the Czech Republic by analysing two sources of data. The incidence of pneumococcal meningitis based on routine notification data varied between 0.4 and 0.6/100 000 population between 1997 and 2006. The incidence of IPD based on laboratory surveillance varied between 2.3 and 4.3/100 000 population between 2000 and 2006. The annual IPD incidence remained stable during the study period. Estimates of absolute IPD case-load in the entire country varied from 235 to 437 per year. The age-specific incidence was highest in the <1 year age group, reaching 4.3/100 000 for pneumococcal meningitis in routine notification and 15.7/100 000 for IPD in laboratory-based surveillance data, respectively. A total of 1236 Streptococcus pneumoniae isolates from cerebrospinal fluid and sterile body sites were investigated. The most frequent serotypes causing IPD in all ages were 3, 4, 14, 8 and 19F, accounting for 41.5% of all isolates. The most frequent serotypes by age group were: <1 year (6B and 19F); 1-4 years (14, 6B and 23F); 40-64 years (3, 8 and 4), and > or = 65 years (3, 4, 9N and 14). The coverage of serotypes in all age groups by pneumococcal vaccines ranged from 41.5% for 7-valent conjugate vaccine to 67.9% for 13-valent conjugate vaccine. The coverage of serotypes causing IPD is significantly different between infants/children and adults/elderly. PCV-7 coverage by age group was: <1 year (66.0%), 1-4 years (65.1%), 40-64 years (34.4%) and > or = 65 years (39.3%). Similar age differences between infants/children and adults/elderly were found in coverage by PCV-9, PCV-11 and PCV-13. The distribution of serotypes in the total population and individual age groups was stable during the period 2000-2006.

Update on childhood pneumococcal vaccination

Since the efficacy of pneumococcal conjugate vaccine (PCV) against invasive pneumococcal disease in young children was first demonstrated in clinical trials in California, USA, in the late 1990s, it has been studied in more diverse populations and introduced into infant vaccination programs in the USA, Australia, Canada and several European countries. This review briefly describes the epidemiology of pneumococcal disease, recent literature on PCV trials in various study populations, the impact of 7-valent PCV infant vaccination on the epidemiology of invasive pneumococcal disease, with special reference to indirect effects in older age groups and the emergence of serotype replacement disease. Variations in vaccine administration schedules, effects on noninvasive pneumococcal diseases, and the use of the polysaccharide pneumococcal vaccine or future formulations of pneumococcal conjugate vaccines from the perspective of policy decisions for population-wide childhood pneumococcal vaccination programs are also highlighted.

Epidemiologic impact of blood culture practices and antibiotic consumption on pneumococcal bacteraemia in children

This study examined the roles of two different diagnostic approaches to children with fever of unknown origin in determining the patterns of pneumococcal bacteraemia in two Spanish regions by comparing their main epidemiologic characteristics. Whereas a blood culture is routinely obtained in this setting in Navarre, this is not generally the case in Majorca. Additionally, the potential role of antibiotic consumption in each region was also analysed. Cumulative incidences in children under the age of 14 years were 26.6 per 100,000 child-years in Navarre (121.1 in children <2 years of age) and 7.3 per 100,000 child-years in Majorca (33.3 in children <2 years of age). In contrast, the incidences per 1,000 blood cultures were similar in both regions. The relative risks of occult bacteraemia, bacteraemic pneumonia and meningitis among the children of Navarre compared to Majorcan children were 11.8, 2.6 and 0.8, respectively. The risk for less virulent (vaccine serotypes plus 6A, 19A and 23A) and for more virulent serotypes (1 and 7) was 4.9 and 3.1 times higher in Navarre, respectively. The number of 7-valent pneumococcal conjugate vaccine (PCV7) doses administered between 2003 and 2004 were also higher in Navarre. Conversely, antibiotic resistance and paediatric prescriptions for broad-spectrum antibiotics were greater in Majorca. Although the most salient differences between both regions, including the effectiveness of pneumococcal conjugate vaccine in Navarre, appeared to be confounded by the higher frequency of blood cultures taken there, certain differences in serotype composition may be explained by the higher antibiotic consumption in Majorca.

Optimal assessment of the ability of children with recurrent respiratory tract infections to produce anti-polysaccharide antibodies

Specific anti-polysaccharide antibody deficiency (SPAD) is an immune disorder. Diagnostic criteria have not yet been defined clearly. One hundred and seventy-six children evaluated for recurrent respiratory tract infections were analysed retrospectively. For each subject, specific anti-pneumococcal antibodies had been measured with two enzyme-linked immunosorbent assays (ELISAs), one overall assay (OA) using the 23-valent pneumococcal polysaccharide vaccine (23-PPSV) as detecting antigen and the other purified pneumococcal polysaccharide serotypes (serotype-specific assay, SSA) (serotypes 14, 19F and 23F). Antibody levels were measured before (n = 176) and after (n = 93) immunization with the 23-PPSV. Before immunization, low titres were found for 138 of 176 patients (78%) with OA, compared to 20 of 176 patients (11%) with the SSA. We found a significant correlation between OA and SSA results. After immunization, 88% (71 of 81) of the patients considered as responders in the OA test were also responders in the SSA; 93% (71 of 76) of the patients classified as responders according to the SSA were also responders in the OA. SPAD was diagnosed in 8% (seven of 93) of patients on the basis of the absence of response in both tests. Thus, we propose to use OA as a screening test for SPAD before 23-PPSV immunization. After immunization, SSA should be used only in case of a low response in OA. Only the absence of or a very low antibody response detected by both tests should be used as a diagnostic criterion for SPAD.

Prevenar™ vaccination: Review of the global data, 2006

The 7-valent pneumococcal conjugate vaccine, Prevenar, was first licensed in the United States in 2000 for the prevention of invasive pneumococcal disease (IPD) caused by the serotypes included in the vaccine. It is presently approved in more than 70 countries, and more than 100 million doses of vaccine have been distributed to date. Within 1 year of routine use in the US, incidence of vaccine-serotype IPD had fallen dramatically among children younger than 2 years, with indirect effects noted among other age groups as well. The most recent data available from the US demonstrates that vaccine-serotype IPD has declined by 94% among the age group recommended for vaccination, and indirect effects have been documented in every unvaccinated age group, including among neonates and young infants. Additionally, declines in other pneumococcal-associated respiratory tract diseases have been reported, highlighting the extended benefits of a Prevenar vaccination program. Subsequently, the vaccine has been introduced into the national immunization programs of several other countries, including Canada, Australia, and The Netherlands. While an increase in disease caused by serotypes not included in the vaccine has been observed ("replacement disease"), the overall impact of this increase has, to date, been small in comparison to the substantial reduction in overall disease burden that has resulted since Prevenar introduction.