Monocyte, Lymphocyte and Neutrophil Ratios - Easy-to-Use Biomarkers for the Diagnosis of Pediatric Tuberculosis.

BACKGROUND: The neutrophil-to-lymphocyte-ratio (NLR), neutrophil-to-monocyte-plus-lymphocyte-ratio (NMLR) and monocyte-to-lymphocyte-ratio (MLR) may have diagnostic potential for tuberculosis (TB). METHODS: Data of two prospective multicenter studies in Switzerland were used, which included children <18 years with TB exposure, infection or disease or with febrile non-TB lower-respiratory-tract infection (nTB-LRTI). RESULTS: Of the 389 children included 25 (6.4%) had TB disease, 12 (3.1%) TB infection, 28 (7.2%) were healthy TB exposed and 324 (83.3%) nTB-LRTI. Median (IQR) NLR was highest with 2.0 (1.2, 2.2) in children with TB disease compared to TB exposed [0.8 (0.6, 1.3); P = 0.002] and nTB-LRTI [0.3 (0.1, 1.0); P < 0.001]. Median (IQR) NMLR was highest with 1.4 (1.2, 1.7) in children with TB disease compared to healthy exposed [0.7 (0.6, 1.1); P = 0.003] and children with nTB-LRTI [0.2 (0.1, 0.6); P < 0.001). Receiver operating characteristic curves to detect TB disease compared to nTB-LRTI for NLR and NMLR had an area under the curve of 0.82 and 0.86, the sensitivity of 88% and 88%, and specificity of 71% and 76%, respectively. CONCLUSION: NLR and NMLR are promising, easy-to-obtain diagnostic biomarkers to differentiate children with TB disease from other lower respiratory tract infections. These results require validation in a larger study and in settings with high and low TB endemicity.

Current status and future directions of post-marketing vaccine safety monitoring with focus on USA and Europe.

Vaccine safety research is a key component of public health programs. Regulatory agencies need to be able to make informed decisions. Public health authorities need to respond to vaccine concerns before they turn into large scale scares reducing vaccine uptake and derailing immunization programs. Several post-licensure vaccine safety monitoring systems have been established in the USA and Europe, and methods such as rapid cycle analysis have been developed for real-time detection and analysis of safety issues. Accurate and reliable vaccine product testing and monitoring requires high quality data of populations of 100 million and above depending on the frequency of the event, vaccine coverage, and the time pressure during which data need to be generated. This requires post-licensure safety studies utilizing large linked population based databases of exposure and outcomes. Harmonized methods for development and linkage of these databases across countries need to be further developed, validated and implemented. Concerted action between the US and Europe could move vaccine safety monitoring to today's level of requirements globally and should be pursued.

Safety of routine childhood vaccine coadministration versus separate vaccination.

INTRODUCTION: As new vaccines are developed more vaccine coadministrations vaccines are being offered to make delivery more practical for health systems and patients. We compared the safety of coadministered vaccines with separate vaccination for 20 coadministrations by considering nine types of adverse events following immunisation (AEFI). METHODS: Real-life immunisation and adverse event data for this observational cohort study were extracted from the Oxford-Royal College of General Practitioners Research and Surveillance Centre for children registered in the database between 2008 and 2018. We applied the self-controlled case series method to calculate relative incidence ratios (RIR) for AEFI. These RIRs compare the RI of AEFI following coadministration with the RI following separate administration of the same vaccines. RESULTS: We assessed 3 518 047 adverse events and included 5 993 290 vaccine doses given to 958 591 children. 17% of AEFI occurred less and 11% more frequently following coadministration than would have been expected based on the RIs following separate vaccinations, while there was no significant difference for 72% of AEFI. We found amplifying interaction effects for AEFI after five coadministrations comprising three vaccines: for fever (RIR 1.93 (95% CI 1.63 to 2.29)), rash (RIR 1.49 (95% CI 1.29 to 1.74)), gastrointestinal events (RIR 1.31 (95% CI 1.14 to 1.49)) and respiratory events (RIR 1.27 (1.17-1.38)) following DTaP/IPV/Hib+MenC+ PCV; gastrointestinal events (RIR 1.65 (95% CI 1.35 to 2.02)) following DTaP/IPV/Hib+MenC+ RV; fever (RIR 1.44 (95% CI 1.09 to 1.90)) and respiratory events (RIR 1.40 (95% CI 1.25 to 1.57)) following DTaP/IPV/Hib+PCV+ RV; gastrointestinal (RIR 1.48 (95% CI 1.20 to 1.82)) and respiratory events (RIR 1.43 (95% CI 1.26 to 1.63)) following MMR+Hib/MenC+PCV; gastrointestinal events (RIR 1.68 (95% CI 1.07 to 2.64)) and general symptoms (RIR 11.83 (95% CI 1.28 to 109.01)) following MMR+MenC+PCV. Coadministration of MMR+PCV led to more fever (RIR 1.91 (95% CI 1.83 to 1.99)), neurological events (RIR 2.04 (95% CI 1.67 to 2.49)) and rash (RIR 1.06 (95% CI 1.01 to 1.11)) compared with separate administration, DTaP/IPV/Hib+MMR to more musculoskeletal events (RIR 3.56 (95% CI 1.21 to 10.50)) and MMR+MenC to more fever (RIR 1.58 (95% CI 1.37 to 1.82)). There was no indication that unscheduled coadministrations are less safe than scheduled coadministrations. CONCLUSION: Real-life RIRs of AEFI justify coadministering routine childhood vaccines according to the immunisation schedule. Further research into the severity of AEFI following coadministration is required for a complete understanding of the burden of these AEFI.

The kinetic profiles of copeptin and mid regional proadrenomedullin (MR-proADM) in pediatric lower respiratory tract infections.

BACKGROUND: Kinetics of copeptin and mid regional proadrenomedullin (MR-proADM) during febrile pediatric lower respiratory tract infections (LRTI) are unknown. We aimed to analyze kinetic profiles of copeptin and MR-proADM and the impact of clinical and laboratory factors on those biomarkers. METHODS: This is a retrospective post-hoc analysis of a randomized controlled trial, evaluating procalcitonin guidance for antibiotic treatment of LRTI (ProPAED-study). In 175 pediatric patients presenting to the emergency department plasma copeptin and MR-proADM concentrations were determined on day 1, 3, and 5. Their association with clinical characteristics and other inflammatory biomarkers were tested by non-linear mixed effect modelling. RESULTS: Median copeptin and MR-proADM values were elevated on day 1 and decreased during on day 3 and 5 (-26%; -34%, respectively). The initial concentrations of MR-proADM at inclusion were higher in patients receiving antibiotics intravenously compared to oral administration (difference 0.62 pmol/L, 95%CI 0.44;1.42, p<0.001). Intensive care unit (ICU) admission was associated with a daily increase of MR-proADM (increase/day 1.03 pmol/L, 95%CI 0.43;1.50, p<0.001). Positive blood culture in patients with antibiotic treatment and negative results on nasopharyngeal aspirates, or negative blood culture were associated with a decreasing MR-proADM (decrease/day -0.85 pmol/L, 95%CI -0.45;-1.44), p<0.001). CONCLUSION: Elevated MR-proADM and increases thereof were associated with ICU admission suggesting the potential as a prognostic factor for severe pediatric LRTI. MR-proADM might only bear limited value for decision making on stopping antibiotics due to its slow decrease. Copeptin had no added value in our setting.

Co-administration of routine paediatric vaccines in England often deviates from the immunisation schedule.

Vaccine co-administration can facilitate the introduction of new vaccines in immunisation schedules and improve coverage. We analysed real life data to quantify the extent of routine paediatric vaccine co-administrations as recommended and as never recommended in the immunisation schedule in England, and assessed factors for recommended and never recommended vaccine co-administrations. Immunisation data for all scheduled routine paediatric vaccines between 2008 and 2018 was obtained from the Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC). We included 6'257'828 doses administered to 1'005'827 children. Twenty-one percent of vaccines were given separately, 79% were co-administered. Sixty-four percent of vaccines scheduled for co-administration were co-administered as recommended while 15% were administered separately. Among all vaccine co-administrations, 75% happened as recommended in the schedule, 4% were never recommended, while 21% deviated from the schedule. Vaccine co-administration according to the schedule varied greatly between vaccines. Forty-eight percent of English children received at least one of their vaccine co-administrations not as recommended in the immunisation schedule, with 19% of children receiving none of their co-administered vaccines as recommended. Late administration of one or more vaccines increased the odds for deviated co-administrations (OR 1.60) and strongly increased the odds for never recommended co-administrations (OR 5.34). Differences between genders, NHS regions, and IMD quintiles were statistically significant but small. Suboptimal co-administration rates for routine paediatric vaccines are a missed opportunity and should be optimised by concerted public health action.

Adherence to the paediatric immunisation schedule in England.

Both adequate coverage and adherence to paediatric immunisation schedules are required for optimal protection against vaccine preventable diseases. We studied the timeliness of routine paediatric vaccinations according to the NHS's immunisation schedule and potential factors of schedule adherence. Immunisation data was obtained from the Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC). We collected vaccine types, doses, and dates for all routine paediatric vaccines between 2008 and 2018: DTaP/IPV/Hib/HepB, DTaP/IPV/Hib, DTaP/IPV, dTaP/IPV, Td/IPV, MMR, PCV, MenB, MenC, MenACWY, Hib/MenC, RV, HPV. Adherence to the immunisation schedule was calculated for each vaccine and dose. Differences in adherence between genders, NHS regions, and IMD quintiles were analysed. Our study included 6'257'828 vaccinations in 1'005'827 children. Seventy-five percent of first doses were administered within one (for vaccines scheduled in the first year of life) or two months (for vaccines scheduled later in life) following the recommended age, 19% too late and 6% too early. About half of the subsequent doses were given timely. The time between first and second doses was too short for 36% of vaccinations while 13% of second doses were administered too long after the first dose. Third doses were administered timely for 45%, too short for 37%, and too long for 18% of vaccinations. Differences in immunisation schedule adherence between girls and boys were negligible, except for HPV, and differences between the four main NHS regions were small. Overall, immunisation schedule adherence improved slightly with decreasing deprivation according to the Index of Multiple Deprivation. Efforts are required to improve the timeliness of paediatric vaccinations and to assure adequate protection against vaccine preventable diseases. We propose developing a compound measure combining coverage and adherence to provide a better indication of the protection against vaccine preventable diseases in a community.

Human metapneumovirus infections--biannual epidemics and clinical findings in children in the region of Basel, Switzerland.

Human metapneumovirus (hMPV) epidemics vary in time and severity. We report findings for PCR for hMPV and respiratory syncytial virus (RSV) performed on nasopharyngeal aspirates (NPA) of hospitalized and outpatient children with respiratory tract infections between October 2004 and April 2008. A total of 3,934 NPAs were tested for hMPV and 3,859 for RSV. Of these, 198 (5%) were hMPV positive and 869 (23%) were RSV-positive. Median age was 17 months and 9 months for hMPV and RSV, respectively. Fifty-nine percent of hMPV and 58% of RSV patients were hospitalized. Proportions of hMPV positive samples for the four winter seasons were 0.4%, 11%, 0.2%, and 14%. For RSV, they were 28%, 15%, 28%, and 28%. HMPV epidemics follow a biannual variation in our area. Major epidemics were observed in winter seasons starting in odd years (2005/06 and 2007/08), minor epidemics in those starting in even years (2004/05 and 2006/07). RSV epidemics usually follow a reciprocal biannual pattern, leading to annually alternating major RSV and hMPV epidemics.

Safety of Co-Administration Versus Separate Administration of the Same Vaccines in Children: A Systematic Literature Review.

The growing number of available vaccines that can be potentially co-administered makes the assessment of the safety of vaccine co-administration increasingly relevant but complex. We aimed to synthesize the available scientific evidence on the safety of vaccine co-administrations in children by performing a systematic literature review of studies assessing the safety of vaccine co-administrations in children between 1999 and 2019, in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Fifty studies compared co-administered vaccines versus the same vaccines administered separately. The most frequently studied vaccines included quadrivalent meningococcal conjugate (MenACWY) vaccine, diphtheria and tetanus toxoids and acellular pertussis (DTaP) or tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccines, diphtheria and tetanus toxoids and acellular pertussis adsorbed, hepatitis B, inactivated poliovirus and Haemophilus influenzae type b conjugate (DTaP-HepB-IPV/Hib) vaccine, measles, mumps, and rubella (MMR) vaccine, and pneumococcal conjugate 7-valent (PCV7) or 13-valent (PCV13) vaccines. Of this, 16% (n = 8) of the studies reported significantly more adverse events following immunization (AEFI) while in 10% (n = 5) significantly fewer adverse events were found in the co-administration groups. Statistically significant differences between co-administration and separate administration were found for 16 adverse events, for 11 different vaccine co-administrations. In general, studies briefly described safety and one-third of studies lacked any statistical assessment of AEFI. Overall, the evidence on the safety of vaccine co-administrations compared to separate vaccine administrations is inconclusive and there is a paucity of large post-licensure studies addressing this issue.

Arthritis and arthralgia as an adverse event following immunization: A systematic literature review.

BACKGROUND: Arthritis and arthralgia are reported as adverse events following immunization with various vaccines. OBJECTIVE: To better understand current knowledge of arthritis and arthralgia as an adverse event following immunization. METHODS: A systematic literature review of Pubmed, Embase, and Cochrane Library was conducted. Data extraction was performed by two independent reviewers. No restrictions on dates were imposed and all types of vaccine studies with primary data were reviewed. RESULTS: Of 343 included studies, there were 206 clinical trials, 90 observational studies, and 47 case reports. Influenza was the most commonly studied vaccine (n = 91, 24.4%). Of the 155 (45.2%) studies addressing causality assessment, 84 studies (54.2%) revealed the assessment method. Only seven clinical trials and 12 observational studies reported a measure of association. Four of these studies examined worsening of arthritic conditions in patients with pre-existing disease. Rigorous assessment of causality was not performed in most studies and many observational studies were prone to bias. CONCLUSIONS: The current evidence linking vaccination to incident arthritis or worsening of arthritic conditions is too heterogeneous and incomplete to infer a causal association. Recommendations for future studies include use of consistent, standardized case definitions and causality assessments, better control of confounding and minimization of bias, and inclusion of measures of associations.

Intussusception in Young Children: Protocol for Multisite Hospital Sentinel Surveillance in India.

India has recently introduced a rotavirus vaccine under a universal immunization program. There is limited information on intussusception, an adverse event, following immunization in children from India. We are conducting sentinel surveillance for intussusception in children aged under two years at 19 hospitals. The sentinel sites' selection followed a multistage process. The surveillance combines retrospective surveillance for 69 months and prospective surveillance for 18 months. The suspected intussusception cases shall be reviewed for capturing confirmed cases and detailed data collection and classification according to Brighton Collaboration criteria. Data shall be analysed to describe epidemiology, trends, regional and seasonal variations, clinical profiles, management modalities, and outcomes of intussusception. The combination of prospective and retrospective surveillance shall be informative about the trend of intussusception over the last seven years in India. At four sites where rotavirus vaccines have been introduced, the change in intussusception trends shall be documented. The potential association with rotavirus vaccines and other vaccines shall be assessed using case-control and self-controlled case series methodology. Results are forthcoming. The results shall support the national vaccine safety surveillance effort by providing baseline estimates of intussusception for continued monitoring. The surveillance protocol and site selection processes shall inform similar vaccine-safety surveillance in India and other developing countries.

Vaccine Update: Recent Progress With Novel Vaccines, and New Approaches to Safety Monitoring and Vaccine Shortage.

Vaccines are increasingly based on new constructs, new technologies, and new compounds. Novel immunization programs are rapidly implemented globally. In this article, we highlight selected hot topics of this highly dynamic and broad field of scientific and public health development. The first section focuses on novel vaccines including malaria, dengue, serogroup B meningococcal, and respiratory syncytial virus vaccines and antibodies. The second section is addressing emerging strategies and programmatic challenges including maternal immunization, integrated mother-child safety monitoring, and finally coping strategies with vaccine shortages.

Narcolepsy and adjuvanted pandemic influenza A (H1N1) 2009 vaccines - Multi-country assessment.

BACKGROUND: In 2010, a safety signal was detected for narcolepsy following vaccination with Pandemrix, an AS03-adjuvanted monovalent pandemic H1N1 influenza (pH1N1) vaccine. To further assess a possible association and inform policy on future use of adjuvants, we conducted a multi-country study of narcolepsy and adjuvanted pH1N1 vaccines. METHODS: We used electronic health databases to conduct a dynamic retrospective cohort study to assess narcolepsy incidence rates (IR) before and during pH1N1 virus circulation, and after pH1N1 vaccination campaigns in Canada, Denmark, Spain, Sweden, Taiwan, the Netherlands, and the United Kingdom. Using a case-control study design, we evaluated the risk of narcolepsy following AS03- and MF59-adjuvanted pH1N1 vaccines in Argentina, Canada, Spain, Switzerland, Taiwan, and the Netherlands. In the Netherlands, we also conducted a case-coverage study in children born between 2004 and 2009. RESULTS: No changes in narcolepsy IRs were observed in any periods in single study sites except Sweden and Taiwan; in Taiwan incidence increased after wild-type pH1N1 virus circulation and in Sweden (a previously identified signaling country), incidence increased after the start of pH1N1 vaccination. No association was observed for Arepanrix-AS03 or Focetria-MF59 adjuvanted pH1N1 vaccines and narcolepsy in children or adults in the case-control study nor for children born between 2004 and 2009 in the Netherlands case-coverage study for Pandemrix-AS03. CONCLUSIONS: Other than elevated narcolepsy IRs in the period after vaccination campaigns in Sweden, we did not find an association between AS03- or MF59-adjuvanted pH1N1 vaccines and narcolepsy in children or adults in the sites studied, although power to evaluate the AS03-adjuvanted Pandemrix brand vaccine was limited in our study.

Procalcitonin for Diagnostics and Treatment Decisions in Pediatric Lower Respiratory Tract Infections.

Mortality and morbidity remain high in pediatric lower respiratory tract infections (LRTIs) despite progress in research and implementation of global diagnostic and treatment strategies in the last decade. Still, 120 million annual episodes of pneumonia affect children younger than 5 years each year leading to 1.3 million fatalities with the major burden of disease carried by low- and middle-income countries (95%). The definition of pneumonia is still challenging. Traditional diagnostic measures (i.e., chest radiographs, C-reactive protein) are unable to distinguish viral and from bacterial etiology. As a result, common antibiotic overuse contributes to growing antibiotic resistance. We present an overview of current evidence from observational and randomized controlled trials on a procalcitonin (PCT)-based diagnosis of pediatric LRTIs and discuss the need for an adequate PCT threshold for antibiotic treatment decision-making.

Immunization in pregnancy clinical research in low- and middle-income countries - Study design, regulatory and safety considerations.

Immunization of pregnant women is a promising public health strategy to reduce morbidity and mortality among both the mothers and their infants. Establishing safety and efficacy of vaccines generally uses a hybrid design between a conventional interventional study and an observational study that requires enrolling thousands of study participants to detect an unknown number of uncommon events. Historically, enrollment of pregnant women in clinical research studies encountered many barriers based on risk aversion, lack of knowledge, and regulatory ambiguity. Conducting research enrolling pregnant women in low- and middle-income countries can have additional factors to address such as limited availability of baseline epidemiologic data on disease burden and maternal and neonatal outcomes during and after pregnancy; challenges in recruiting and retaining pregnant women in research studies, variability in applying and interpreting assessment methods, and variability in locally acceptable and available infrastructure. Some measures to address these challenges include adjustment of study design, tailoring recruitment, consent process, retention strategies, operational and logistical processes, and the use of definitions and data collection methods that will align with efforts globally.

Drivers of antibiotic prescribing in children and adolescents with febrile lower respiratory tract infections.

BACKGROUND: Knowledge of key drivers for antibiotic prescribing in pediatric lower respiratory tract infection (LRTI) could support rational antibiotic use. Thus, we aimed to determine the impact of clinical and laboratory factors on antibiotic prescribing in children and adolescents with febrile LRTI. METHODS: Pediatric patients from the standard care control group of a randomized controlled trial (ProPAED) investigating procalcitonin guided antibiotic treatment in febrile LRTI were included in a multivariate logistic regression analysis to evaluate the impact of laboratory and clinical factors on antibiotic prescribing. RESULTS: The standard care control group of the ProPAED study comprised 165 LRTI patients (median age: 2.7 years, range: 0.1-16), out of which 88 (55%) received antibiotic treatment. Factors significantly associated with antibiotic prescribing in patients with complete clinical and laboratory documentation (n = 158) were C-reactive protein (OR 5.8 for a 10-fold increase, 95%CI 2.2-14.9), white blood count beyond age-dependent reference range (OR 3.9, 95%CI 1.4-11.4), body temperature (OR 1.7 for an increase by 1°C, 95%CI 1.02-2.68), and pleuritic pain (OR 2.8, 95%CI 1.1-7.6). Dyspnea (OR 0.3, 95%CI 0.1-0.7) and wheezing (OR 0.3, 95%CI 0.13-0.95) were inversely associated with antibiotic prescribing. CONCLUSION: Laboratory markers were strong drivers of antibiotic prescribing in children with febrile lower respiratory tract infections, in spite of their known poor prediction of antibiotic need. Building on current guidelines for antibiotic treatment in children with febrile LRTI, a reliable decision algorithm for safe antibiotic withholding considering the laboratory and clinical factors evaluated in this study has the potential to further reduce antibiotic prescribing.

Kawasaki disease and immunisation: A systematic review.

BACKGROUND: Kawasaki disease is a complex and potentially serious condition. It has been observed in temporal relation to immunisation. METHODS: We conducted a systematic literature review using various reference sources to review the available evidence published in the literature. RESULTS: We identified twenty seven publications reporting a temporal association between immunisation and Kawasaki disease. We present a systematic review of data drawn from randomised controlled trials, observational studies, case series and reports, and reviews. Overall there was a lack of standardised case definitions, making data interpretation and comparability challenging. CONCLUSIONS: Although a temporal relationship between immunisation and Kawasaki disease is suggested, evidence for an increased risk or a causal association is lacking. Implementation of a standardised Kawasaki disease case definition would increase confidence in the findings and add value to future studies of pre- or post-licensure vaccine safety studies.

Pandemic influenza vaccine & narcolepsy: simulations on the potential impact of bias.

Several studies have identified an association between Pandemrix(TM), an AS03 adjuvanted pandemic influenza A(H1N1) vaccine, and narcolepsy, a rare and under-diagnosed sleep disorder with a median onset-to-diagnosis interval of ten years. This paper reviews potential sources of bias in published studies and aims to provide, through simulation, methodological recommendations for assessment of vaccine safety signals. Our simulation study showed that in the absence of an association between the vaccine and the outcome, presence of detection bias and differential exposure misclassification could account for elevated risk estimates. These may play a major role, particularly in alert situations when observation times are limited and the disease has a long latency period. Estimates from the case-control design were less inflated than those from the cohort design when these biases were present. Overall, these simulations provide useful insights for the design and interpretation of future studies.

Evaluation of a multinational, multilingual vaccine debate on Twitter.

BACKGROUND: Public confidence in an immunization programme is a pivotal determinant of the programme's success. The mining of social media is increasingly employed to provide insight into the public's sentiment. This research further explores the value of monitoring social media to understand public sentiment about an international vaccination programme. OBJECTIVE: To gain insight into international public discussion on the paediatric pentavalent vaccine (DTP-HepB-Hib) programme by analysing Twitter messages. METHODS: Using a multilingual search, we retrospectively collected all public Twitter messages mentioning the DTP-HepB-Hib vaccine from July 2006 until May 2015. We analysed message characteristics by frequency of referencing other websites, type of websites, and geographic focus of the discussion. In addition, a sample of messages was manually annotated for positive or negative message tone. RESULTS: We retrieved 5771 messages. Only 3.1% of the messages were reactions to other messages, and 86.6% referred to websites, mostly news sites (70.7%), other social media (9.8%), and health-information sites (9.5%). Country mentions were identified in 70.4% of the messages, of which India (35.4%), Indonesia (18.3%), and Vietnam (13.9%) were the most prevalent. In the annotated sample, 63% of the messages showed a positive or neutral sentiment about DTP-HepB-Hib. Peaks in negative and positive messages could be related to country-specific programme events. CONCLUSIONS: Public messages about DTP-HepB-Hib were characterized by little interaction between tweeters, and by frequent referencing of websites and other information links. Twitter messages can indirectly reflect the public's opinion about major events in the debates about the DTP-HepB-Hib vaccine.

Reference set for performance testing of pediatric vaccine safety signal detection methods and systems.

BACKGROUND: Safety signal detection in spontaneous reporting system databases and electronic healthcare records is key to detection of previously unknown adverse events following immunization. Various statistical methods for signal detection in these different datasources have been developed, however none are geared to the pediatric population and none specifically to vaccines. A reference set comprising pediatric vaccine-adverse event pairs is required for reliable performance testing of statistical methods within and across data sources. METHODS: The study was conducted within the context of the Global Research in Paediatrics (GRiP) project, as part of the seventh framework programme (FP7) of the European Commission. Criteria for the selection of vaccines considered in the reference set were routine and global use in the pediatric population. Adverse events were primarily selected based on importance. Outcome based systematic literature searches were performed for all identified vaccine-adverse event pairs and complemented by expert committee reports, evidence based decision support systems (e.g. Micromedex), and summaries of product characteristics. Classification into positive (PC) and negative control (NC) pairs was performed by two independent reviewers according to a pre-defined algorithm and discussed for consensus in case of disagreement. RESULTS: We selected 13 vaccines and 14 adverse events to be included in the reference set. From a total of 182 vaccine-adverse event pairs, we classified 18 as PC, 113 as NC and 51 as unclassifiable. Most classifications (91) were based on literature review, 45 were based on expert committee reports, and for 46 vaccine-adverse event pairs, an underlying pathomechanism was not plausible classifying the association as NC. CONCLUSION: A reference set of vaccine-adverse event pairs was developed. We propose its use for comparing signal detection methods and systems in the pediatric population.