CASE CONTROL STUDY MEASURING INFLUENZA VACCINE EFFECTIVENESS IN HUNGARY
Dr. Marta Melles, director general
Project Coordination Center
National Center for Epidemiology
Department of Epidemiology2-6. Gyáli street Budapest H-1097
Phone: + 36 1 4761100/ 2131Fax: + 36 1 2151792E-Mail: email@example.com
Introduction of the project
Resulting from the constant evolution of influenza viruses, influenza vaccine effectiveness (IVE) can vary from year to year depending on the matching between the circulating strains and the ones that are included in the vaccine.
Vaccine efficacy studies using serological outcomes are performed before the influenza seasons. Having annual influenza IVE estimates during and after the influenza season using laboratory confirmed influenza-like illness (ILI) as an outcome is important, because it provides additional information regarding the impact of current vaccination strategies on the burden of disease. Based on this information, decisions can be made to implement complementary public health measures if the vaccine is less effective due to vaccine mismatch.
The results of vaccine effectiveness study can be used to
It is important to establish networks and systems that are able to provide such data and flexible enough to be adapted to a fast evolving situation like pandemic influenza, because such network and a solid expertise cannot be developed within a short time period.
During the 2008-2009 influenza season, the European Centre for Disease Prevention and Control (ECDC) funded five pilot case control studies, including one in Hungary, to measure influenza vaccine effectiveness among the elderly (>= 60 years old). The pilot study in Hungary was based on GP surveillance networks. We used ILI EU case definition. We collected data about exposure and a commonly agreed set of variables to adjust for positive and negative confounding. We used two sets of controls: ILI flu negative controls and GP clients not having presented with ILI during the season to test which one is the best, feasible and sustainable to use in our setting. We contributed to the pooled analysis which provided an IVE estimate on European level.
After finishing the pilot case control study among the elderly, the Hungarian study team has developed another protocol during the spring of 2009 for the 2009-2010 influenza season to measure IVE. Seven countries, including France, Hungary, Ireland, Italy, Portugal, Romania, Spain were chosen and received funding to perform case control studies with similar protocols to contribute to the early EU-level estimate of pandemic influenza vaccine effectiveness.
In the meantime a new influenza A virus causing human infections was reported from the USA and from Mexico. The epidemic situation evolved rapidly, and the WHO raised the pandemic alert level to 6 on 11 June 2009. As soon as the new virus was identified by the WHO as a candidate virus for vaccine manufacturing, a number of vaccine manufacturers started to develop a new vaccine. Hungary has national vaccine manufacturing capacity, which supplies the country with both pandemic and seasonal influenza vaccines. This capacity made it possible to have enough pandemic influenza vaccine available for the population early, to be able to start vaccination campaign among the first few countries on Earth. We modified the study protocol to adapt to the pandemic situation to be able to measure both seasonal and pandemic IVE during 2009-10 influenza season among not only the elderly, but in all the 18+ population. The Hungarian results of the study were presented in the I-MOVE workshop (Budapest 17-20 May 2010), where all the results of the other countries for the 2009-10 studies were presented and discussed. The pooled results of the case-control studies are under publication.
I-MOVE Conference and Workshop in Budapest, May 2010 - photos
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