88 research outputs found
Estimating the population prevalence and force of infection directly from antibody titres
No full textAbstract: The use of threshold values in order to diagnose individual subjects as being 'susceptible' or 'infected or recovered/immune' for a specific infection is virtually always prone to false positive, false negative or inconclusive classifications. Such misclassifications might lead to biased estimates for epidemiological parameters, such as the prevalence and the force of infection. In this article, we propose to estimate these epidemiological parameters directly from antibody titres, using an underlying mixture model. The method is applied to estimate the Salmonella serological prevalence in pigs and the age-dependent force of infection using serological data on the Varicella-Zoster virus (VZV) in humans. The threshold and direct method are compared through a simulation study
A systematic review of varicella seroprevalence in European countries before universal childhood immunization : deriving incidence from seroprevalence data
No full textAbstract: Surveillance systems for varicella in Europe are highly heterogeneous or completely absent. We estimated the varicella incidence based on seroprevalence data, as these data are largely available and not biased by under-reporting or underascertainment. We conducted a systematic literature search for varicella serological data in Europe prior to introduction of universal varicella immunization. Age-specific serological data were pooled by country and serological profiles estimated using the catalytic model with piecewise constant force of infection. From the estimated profiles, we derived the annual incidence of varicella infection (/100.000) for six age groups (<5, 5-9, 10-14, 15-19, 20-39 and 40-65 years). In total, 43 studies from 16 countries were identified. By the age of 15 years, over 90% of the population has been infected by varicella in all countries except for Greece (86.6%) and Italy (85.3%). Substantial variability across countries exists in the age-specific annual incidence of varicella primary infection among the <5 years old (from 7052 to 16 122 per 100 000) and 5-9 years old (from 3292 to 11 798 per 100 000). The apparent validity and robustness of our estimates highlight the importance of serological data for the characterization of varicella epidemiology, even in the absence of sampling or assay standardization
Vaccine effectiveness against laboratory-confirmed influenza in Europe – Results from the DRIVE network during season 2018/19
No full textThe DRIVE project aims to establish a sustainable network to estimate brand-specific influenza vaccine effectiveness (IVE) annually. DRIVE is a public–private partnership launched in response to EMA guidance that requires effectiveness evaluation from manufacturers for all individual influenza vaccine brands every season. IVE studies are conducted by public partners in DRIVE. Private partners (vaccine manufacturers from the European Federation of Pharmaceutical Industries and Association (EFPIA)) provide written feedback moderated by an independent scientific committee.
Test-negative design (TND) case-control studies (4 in primary care and five in hospital) were conducted in six countries in Europe during the 2018/19 season. Site-specific confounder-adjusted vaccine effectiveness (VE) estimates for any vaccine exposure were calculated by age group (<18 years (y), 18-64y and 65 + y) and pooled by setting (primary care, hospital) through random effects meta-analysis. In addition, one population-based cohort study was conducted in Finland.
TND studies included 3339 cases and 6012 controls; seven vaccine brands were reported. For ages 65 + y, pooled VE against any influenza strain was estimated at 27% (95%CI 6–44) in hospital setting. Sample size was insufficient for meaningful IVE estimates in other age groups, in the primary care setting, or by vaccine brand.
The population-based cohort study included 274,077 vaccinated and 494,337 unvaccinated person-years, two vaccine brands were reported. Brand-specific IVE was estimated for Fluenz Tetra (36% [95%CI 24–45]) for ages 2-6y, Vaxigrip Tetra (54% [43–62]) for ages 6 months to 6y, and Vaxigrip Tetra (30% [25–35]) for ages 65 + y.
The results presented are from the second influenza season covered by the DRIVE network. While sample size from the pooled TND studies was still too low for precise (brand-specific) IVE estimates, the network has approximately doubled in size compared to the pilot season. Taking measures to increase sample size is an important focus of DRIVE for the coming years
Vaccine effectiveness against laboratory-confirmed influenza in Europe – Results from the DRIVE network during season 2018/19
No full textThe DRIVE project aims to establish a sustainable network to estimate brand-specific influenza vaccine effectiveness (IVE) annually. DRIVE is a public–private partnership launched in response to EMA guidance that requires effectiveness evaluation from manufacturers for all individual influenza vaccine brands every season. IVE studies are conducted by public partners in DRIVE. Private partners (vaccine manufacturers from the European Federation of Pharmaceutical Industries and Association (EFPIA)) provide written feedback moderated by an independent scientific committee. Test-negative design (TND) case-control studies (4 in primary care and five in hospital) were conducted in six countries in Europe during the 2018/19 season. Site-specific confounder-adjusted vaccine effectiveness (VE) estimates for any vaccine exposure were calculated by age group (<18 years (y), 18-64y and 65 + y) and pooled by setting (primary care, hospital) through random effects meta-analysis. In addition, one population-based cohort study was conducted in Finland. TND studies included 3339 cases and 6012 controls; seven vaccine brands were reported. For ages 65 + y, pooled VE against any influenza strain was estimated at 27% (95%CI 6–44) in hospital setting. Sample size was insufficient for meaningful IVE estimates in other age groups, in the primary care setting, or by vaccine brand. The population-based cohort study included 274,077 vaccinated and 494,337 unvaccinated person-years, two vaccine brands were reported. Brand-specific IVE was estimated for Fluenz Tetra (36% [95%CI 24–45]) for ages 2-6y, Vaxigrip Tetra (54% [43–62]) for ages 6 months to 6y, and Vaxigrip Tetra (30% [25–35]) for ages 65 + y. The results presented are from the second influenza season covered by the DRIVE network. While sample size from the pooled TND studies was still too low for precise (brand-specific) IVE estimates, the network has approximately doubled in size compared to the pilot season. Taking measures to increase sample size is an important focus of DRIVE for the coming years
Zoster Vaccine Effectiveness Against Incident Herpes Zoster and Post-Herpetic Neuralgia In Elderly In The UK
No full textHow to reduce effectively the risk of human salmonellosis from minced pork meat in Belgium
No full textIntroduction
Since the last ten years, quantitative microbial risk assessments (QMRA) concerning food borne pathogens have been developed in different countries. To improve pork meat safety further, the Belgian authorities have asked to an interdisciplinary Belgian research consortium (METZOON-consortium) the development of a “farm to fork” QMRA concerning the consumption of fresh minced pork meat contaminated with Salmonella in Belgium. The final task of this QMRA is to give practical recommendations to improve the pork meat safety and to reduce the number of salmonellosis cases in Belgium. These recommendations are based on reduction scenario’s introduced in the model.
Materiel and methods
The METZOON model was carried out by building a modular risk model covering the pork meat production chain and developed into six consecutive modules: farm, transport and lairage, slaughterhouse, post processing, distribution and storage, preparation at home. The risk characterization is the dose response model developed by Bollaerts et al.; based on outbreak data (1). The scenario analysis helps to identify combinations of input values which lead to output target values (3). This is achieved by selecting various combinations of input values commonly know as “what if scenario”. The selected scenarios were based on the recent literature and on concrete management and technical options to improve the microbiological quality of the pork meat and to reduce effectively the risk of human salmonellosis. First, single interventions were assessed like reducing the seroprevalence at farm level, reducing the prevalence of contaminated carcasses and their contamination levels at slaughterhouse, decontamination of the carcasses with double singing at slaughterhouse, reduction of cross-contamination at home, etc. A second step was to assessed multiple interventions along the production chain, by example, joined efforts by farmers at primary production, by operators at slaughterhouse and consumers at home simultaneously.
Discussion and conclusions
The scenario analysis can provide new microbiological criteria to reach a food safety objective in order to reduce the risk of human salmonellosis. Most single intervention and control measures are not effective enough to reduce or remove a Salmonella infection or contamination from the pig production chain. It is therefore recommended that interventions and control strategy is formulated, based on a combination of measures which are both practically and economically feasible. Technical solutions, like systematic double singing or reduction of contamination at evisceration by enclosure of the rectum could improve the Belgian situation (2). The consumers must also be aware of good hygiene practices during preparation of the meat at home. Undercooking and cross contamination with raw food can be avoided by changing the habit and the behavior of the household cook. The results of these scenarios are useful for the actors involved in the pork meat chain and for public health officials
Développement et validation d'un protocole d'étude sérologique et lié au comportement des infections par VHB, VHC et VIH chez les toxicomanes ayant consommé des drogues par injection dans un passé récent (DRID)
No full textEstimation of vaccination coverage from electronic healthcare records; methods performance evaluation - A contribution of the ADVANCE-project
No full textINTRODUCTION: The Accelerated Development of VAccine beNefit-risk Collaboration in Europe (ADVANCE) is a public private collaboration aiming to develop and test a system for rapid benefit-risk (B/R) monitoring of vaccines, using existing electronic healthcare record (eHR) databases in Europe. Part of the data in such sources is missing due to incomplete follow-up hampering the accurate estimation of vaccination coverage. We compared different methods for coverage estimation from eHR databases; naïve period prevalence, complete case period prevalence, period prevalence adjusted for follow-up time, Kaplan-Meier (KM) analysis and (adjusted) inverse probability weighing (IPW). METHODS: We created simulation scenarios with different proportions of completeness of follow-up. Both completeness independent and dependent from vaccination date and status were considered. The root mean squared error (RMSE) and relative difference between the estimated and true coverage were used to assess the performance of the different methods for each of the scenarios. We included data examples on the vaccination coverage of human papilloma virus and pertussis component containing vaccines from the Spanish BIFAP database. RESULTS: Under completeness independent from vaccination date or status, several methods provided estimates with bias close to zero. However, when dependence between completeness of follow-up and vaccination date or status was present, all methods generated biased estimates. The IPW/CDF methods were generally the least biased. Preference for a specific method should be based on the type of censoring and type of dependence between completeness of follow-up and vaccination. Additional insights into these aspects, might be gained by applying several methods
Thyroid Cancer Incidence around the Belgian Nuclear Sites, 2000–2014
No full text<p>The present study investigates whether there is an excess incidence of thyroid cancer among people living in the vicinity of the nuclear sites in Belgium. Adjusted Rate Ratios were obtained from Poisson regressions for proximity areas of varying sizes. In addition, focused hypothesis tests and generalized additive models were performed to test the hypothesis of a gradient in thyroid cancer incidence with increasing levels of surrogate exposures. Residential proximity to the nuclear site, prevailing dominant winds frequency from the site, and simulated radioactive discharges were used as surrogate exposures. No excess incidence of thyroid cancer was observed around the nuclear power plants of Doel or Tihange. In contrast, increases in thyroid cancer incidence were found around the nuclear sites of Mol-Dessel and Fleurus; risk ratios were borderline not significant. For Mol-Dessel, there was evidence for a gradient in thyroid cancer incidence with increased proximity, prevailing winds, and simulated radioactive discharges. For Fleurus, a gradient was observed with increasing prevailing winds and, to a lesser extent, with increasing simulated radioactive discharges. This study strengthens earlier findings and suggests increased incidences in thyroid cancer around two of the four Belgian nuclear sites. Further analyses will be performed at a more detailed geographical level.</p></p
Ontwikkeling en validatie van een serologisch en gedragsgerelateerd studieprotocol naar HCV-, HBV- en HIV-infecties bij recent injecterende drugsgebruikers tot realisatie van de registratie van de drugs related infectious diseases (DRID)
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