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Commentary to the recent study by Wang et al.
No full textThe author(s) received no financial support for the research, authorship, and/or publication of this article
Optimising the case-crossover design for use in shared exposure settings
No full textAbstract: With a case-crossover design, a case's exposure during a risk period is compared to the case's exposures at referent periods. The selection of referents for this self-controlled design is determined by the referent selection strategy (RSS). Previous research mainly focused on systematic bias associated with the RSS. We additionally focused on how RSS determines the number of referents per risk, sensitivity to overdispersion and time-varying confounding. We illustrated the consequences of different RSS using a simulation study informed by data on meteorological variables and Legionnaires' disease. By randomising the events and exposure time series, we explored statistical power associated with time-stratified and fixed bidirectional RSS and their susceptibility to systematic bias and confounding bias. In addition, we investigated how a high number of events on the same date (e.g. outbreaks) affected coefficient estimation. As illustrated by our work, referent selection alone can be insufficient to control for a time-varying confounding bias. In contrast to systematic bias, confounding bias can be hard to detect. We studied potential solutions: varying the model parameters and link-function, outlier-removal and aggregating the input-data over smaller areas. Our simulation study offers a framework for researchers looking to detect and to avoid bias in case-crossover studies
Multivariate phenomenological models for real-time short-term forecasts of hospital capacity for covid-19 in Belgium from March to June 2020
No full textAbstract: Phenomenological models are popular for describing the epidemic curve. We present how they can be used at different phases in the epidemic, by modelling the daily number of new hospitalisations (or cases). As real-time prediction of the hospital capacity is important, a joint model of the new hospitalisations, number of patients in hospital and in intensive care unit (ICU) is proposed. This model allows estimation of the length of stay in hospital and ICU, even if no (or limited) individual level information on length of stay is available. Estimation is done in a Bayesian framework. In this framework, real-time alarms, defined as the probability of exceeding hospital capacity, can be easily derived. The methods are illustrated using data from the COVID-19 pandemic in March-June 2020 in Belgium, but are widely applicable
Short-term associations between Legionnaires' disease incidence and meteorological variables in Belgium, 2011-2019
No full textAbstract: The number of reported cases with Legionnaires' disease (LD) is increasing in Belgium. Previous studies have investigated the associations between LD incidence and meteorological factors, but the Belgian data remained unexplored. We investigated data collected between 2011 and 2019. Daily exposure data on temperature, relative humidity, precipitation and wind speed was obtained from the Royal Meteorological Institute for 29 weather stations. Case data were collected from the national reference centre and through mandatory notification. Daily case and exposure data were aggregated by province. We conducted a time-stratified case-crossover study. The 'at risk' period was defined as 10 to 2 days prior to disease onset. The corresponding days in the other study years were selected as referents. We fitted separate conditional Poisson models for each day in the 'at risk' period and a distributed lag non-linear model (DLNM) which fitted all data in one model. LD incidence showed a yearly peak in August and September. A total of 614 cases were included. Given seasonality, a sequence of precipitation, followed by high relative humidity and low wind speed showed a statistically significant association with the number of cases 6 to 4 days later. We discussed the advantages of DLNM in this context
Dynamic changes in paediatric invasive pneumococcal disease after sequential switches of conjugate vaccine in Belgium: a national retrospective observational study
No full textBACKGROUND: Ten-valent and 13-valent pneumococcal conjugate vaccines (PCVs) have shown important benefits by decreasing invasive pneumococcal disease caused by vaccine serotypes. Belgium had an uncommon situation with sequential use of PCV7, PCV13, and PCV10 in the childhood vaccination programmes between 2007 and 2018. We aimed to analyse the changes in incidence of invasive pneumococcal disease and serotype distribution in children throughout this period. METHODS: Streptococcus pneumoniae isolates were obtained from patients with invasive pneumococcal disease in Belgium between 2007 and 2018 by the national laboratory-based surveillance. Paediatric invasive pneumococcal disease incidence, serotype distribution, and antimicrobial susceptibility were analysed in periods during which PCV7 (2009-10), PCV13 (2013-14), both PCV13 and PCV10 (2015-16), and PCV10 (2017-18) were used. Incidence rates and trends were compared. Vaccination status was collected. For a subset of serotype 19A isolates, multilocus sequence type was identified. FINDINGS: After a decrease in PCV7 serotype invasive pneumococcal disease was observed during the PCV7 period, total paediatric invasive pneumococcal disease incidence significantly declined during the PCV13 period (-2·6% monthly, p<0·0001). During the PCV13-PCV10 period (2015-16), the lowest mean in paediatric invasive pneumococcal disease incidence was achieved, but the incidence increased again during the PCV10 period (2017-18), especially in children younger than 2 years (+1·7% monthly; p=0·028). This increase was mainly due to a significant rise in serotype 19A invasive pneumococcal disease incidence in the PCV10 period compared with the PCV13 period (p<0·0001), making serotype 19A the predominant serotype in paediatric invasive pneumococcal disease in the PCV10 period. Genetic diversity within the 2017-18 serotype 19A collection was seen, with two predominant clones, ST416 and ST994, that were infrequently observed before PCV10 introduction. In 2018, among children younger than 5 years with invasive pneumococcal disease who were correctly vaccinated, 37% (37 of 100) had PCV13 serotype invasive pneumococcal disease, all caused by serotype 19A and serotype 3. INTERPRETATION: After a significant decrease during the PCV13 period, paediatric invasive pneumococcal disease incidence increased again during the PCV10 period. This observation mainly resulted from a significant increase of serotype 19A cases. During the PCV10 period, dominant serotype 19A clones differed from those detected during previous vaccine periods. Whether changes in epidemiology resulted from the vaccine switch or also from natural evolution remains to be further elucidated. FUNDING: The Belgian National Reference is funded by the Belgian National Institute for Health and Disability Insurance and the whole genome sequencing by an investigator-initiated research grant from Pfizer.sponsorship: The Belgian National Reference is funded by the Belgian National Institute for Health and Disability Insurance and the whole genome sequencing by an investigator-initiated research grant from Pfizer. (Belgian National Institute for Health and Disability Insurance, Pfizer)status: Publishe
Serial Intervals for SARS-CoV-2 Omicron and Delta Variants, Belgium, November 19–December 31, 2021
No full textWe investigated the serial interval for SARS-CoV-2 Omicron BA.1 and Delta variants and observed a shorter serial interval for Omicron, suggesting faster transmission. Results indicate a relationship between empirical serial interval and vaccination status for both variants. Further assessment of the causes and extent of Omicron dominance over Delta is warranted
Capture-Recapture Estimators in Epidemiology with Applications to Pertussis and Pneumococcal Invasive Disease Surveillance.
No full textSurveillance networks are often not exhaustive nor completely complementary. In such situations, capture-recapture methods can be used for incidence estimation. The choice of estimator and their robustness with respect to the homogeneity and independence assumptions are however not well documented.We investigated the performance of five different capture-recapture estimators in a simulation study. Eight different scenarios were used to detect and combine case-information. The scenarios increasingly violated assumptions of independence of samples and homogeneity of detection probabilities. Belgian datasets on invasive pneumococcal disease (IPD) and pertussis provided motivating examples.No estimator was unbiased in all scenarios. Performance of the parametric estimators depended on how much of the dependency and heterogeneity were correctly modelled. Model building was limited by parameter estimability, availability of additional information (e.g. covariates) and the possibilities inherent to the method. In the most complex scenario, methods that allowed for detection probabilities conditional on previous detections estimated the total population size within a 20-30% error-range. Parametric estimators remained stable if individual data sources lost up to 50% of their data. The investigated non-parametric methods were more susceptible to data loss and their performance was linked to the dependence between samples; overestimating in scenarios with little dependence, underestimating in others. Issues with parameter estimability made it impossible to model all suggested relations between samples for the IPD and pertussis datasets. For IPD, the estimates for the Belgian incidence for cases aged 50 years and older ranged from 44 to58/100,000 in 2010. The estimates for pertussis (all ages, Belgium, 2014) ranged from 24.2 to30.8/100,000.We encourage the use of capture-recapture methods, but epidemiologists should preferably include datasets for which the underlying dependency structure is not too complex, a priori investigate this structure, compensate for it within the model and interpret the results with the remaining unmodelled heterogeneity in mind
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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