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Le Touquet – Paris-Plage, France

Le Polain de Waroux O.,Public Health England | Le Polain de Waroux O.,U.S. Center for Disease Control and Prevention | Maguire H.,Public Health England | Maguire H.,U.S. Center for Disease Control and Prevention | Moren A.,EpiConcept
Eurosurveillance | Year: 2012

The use of the case-cohort design for outbreak investigations has been limited. Here we discuss its strengths and limitations based on real and fictitious examples. The case-cohort is a case-control study where controls are sampled from the initial population at risk, and may thus include both cases and non-cases. An advantage of the design, compared to traditional case-control studies, is that risk ratios can easily be obtained directly from the cross-product of exposed and unexposed cases and controls (rare disease assumption is not required). We illustrate this in the context of point source gastrointestinal outbreaks and in field studies on vaccine effectiveness. The design is also useful to investigate multiple outcomes with a unique sample of controls or to test hypotheses when different case-definitions (from the most sensitive to the most specific) are used for a particular outcome. Strengths and limitations are presented, and discussed in the context of outbreak investigations.

Valenciano M.,EpiConcept | Ciancio B.C.,U.S. Center for Disease Control and Prevention
Eurosurveillance | Year: 2012

Since 2007, the European Centre for Disease Prevention and Control (ECDC) has supported I-MOVE (influenza monitoring vaccine effectiveness), a network to monitor seasonal and pandemic influenza vaccine effectiveness (IVE) in the European Union (EU) and European Economic Area (EEA). To set up I-MOVE, we conducted a literature review and a survey on methods used in the EU/EEA to measure IVE and held expert consultations to guide the development of generic protocols to estimate IVE in the EU/EEA. On the basis of these protocols, from the 2008/09 season, I-MOVE teams have conducted multicentre case-control, cohort and screening method studies, undertaken within existing sentinel influenza surveillance systems. The estimates obtained include effectiveness against medically attended laboratory-confirmed influenza and are adjusted for the main confounding factors described in the literature. I-MOVE studies are methodologically sound and feasible: The availability of various study designs, settings and outcomes provides complementary evidence, facilitating the interpretation of the results. The IVE estimates have been useful in helping to guide influenza vaccine policy at national and European level. I-MOVE is a unique platform for exchanging views on methods to estimate IVE. The scientific knowledge and experience in practical, managerial and logistic issues can be adapted to monitor surveillance of the effectiveness of other vaccines.

Valenciano M.,EpiConcept
Euro surveillance : bulletin européen sur les maladies transmissibles = European communicable disease bulletin | Year: 2013

We conducted a test-negative case-control study based in five European sentinel surveillance networks. The early 2012/13 adjusted influenza vaccine effectiveness was 78.2% (95% CI: 18.0 to 94.2) against influenza B, 62.1% (95% CI: -22.9 to 88.3%) against A(H1) pdm09, 41.9 (95% CI: -67.1 to 79.8) against A(H3N2) and 50.4% (95% CI: -20.7 to 79.6) against all influenza types in the target groups for vaccination. Efforts to improve influenza vaccines should continue to better protect those at risk of severe illness or complications.

The I-MOVE\ Consortium includes European Union (EU) Public Health Institutes, SME and Universities. It aims at measuring and comparing the effectiveness (VE) and impact (VI) of influenza and Pneumococcal vaccines and vaccination strategies a in the elderly population in Europe. The goal is to develop a sustainable platform of primary care practices, hospitals and laboratory networks that share validated methods to evaluate post marketing vaccine performances. The objectives are to identify, pilot test, and disseminate in EU the best study designs to measure, on a real time basis, VE (direct effect) and the VI of vaccination programmes (indirect and overall effect) against laboratory confirmed cases of influenza (types/subtypes) and pneumococcal disease (serotypes), and clinical outcomes. Cost effectiveness analysis will be conducted. Results will allow to understand factors affecting specific VE, the duration of protection of influenza and pneumococcal vaccines, the interaction between vaccines, the role of repeated vaccinations, the occurrence of serotype replacement (pneumococcus); identify vaccine types and brands with low VE; guide the decision of the WHO committees on vaccine strain selection (influenza); provide robust benefit indicators (VE and VI) and cost benefit and effectiveness results; guide vaccination strategies (schedules, doses, boosters). This EU member state collaboration will respond to questions that require studies based on large sample sizes and sharing of expertise that cannot be achieved by one country alone. It will allow the best methods to be used and results to benefit to all EU countries whatever their current public health achievements. Results will be shared with international partners.

Hanquet G.,Ghent University | Valenciano M.,EpiConcept | Moren A.,EpiConcept
Vaccine | Year: 2013

Once a vaccine is licensed and introduced in the population, post-licensure studies are required to measure vaccine effectiveness and impact of vaccination programmes on the population at large. However, confusion still prevails around these concepts, making it difficult to discern which effects are measured in such studies and how their findings should be interpreted. We review from the public health evaluation perspective the effects of vaccine-related exposures, describe the methods used to measure them and their assumptions.We distinguish effects due to exposure to individual vaccination from those due to exposure to a vaccination programme, as the latter depends on vaccine coverage, other population factors and includes indirect effects as well. Vaccine (direct) effectiveness is estimated by comparing vaccinated and unvaccinated individuals exposed to the same vaccination programme. The impact of a vaccination programme, defined here as the population prevented fraction when exposure is the programme, is measured by comparing populations with and without a vaccination programme, most commonly the same population before and after vaccination. These designs are based on a number of assumptions for valid inference. In particular, they assume that vaccinees and non-vaccinees do not differ in terms of susceptibility and exposure to the disease or in ascertainment of vaccination and disease status. In pre and post-vaccination design, the population is assumed to have similar baseline transmission, case detection and reporting, risk factors and medical practices in both periods.These principles are frequently violated in post-licensure studies. Potential confounding and biases must be minimized in study design and analyses, or taken into account during result interpretation. It is also essential to define which exposure is evaluated (individual vaccination or vaccination programme) and which effect is measured. This may help decision-makers clarify which type of study is needed and how to interpret the results. © 2013 Elsevier Ltd.

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