Does a population survey provide reliable influenza vaccine uptake rates among high-risk groups? A case-study of The Netherlands
Introduction
All European countries have recommendations for influenza vaccination among the elderly and chronically ill [1]. However, only a few countries are able to provide data on vaccination uptake among these groups. About half of the European countries are able to report uptake rates for the elderly, and a few countries are able to do so for the other groups at risk [2]. However, insight into vaccination uptake among different groups is essential for monitoring and evaluating national influenza vaccination campaigns, and for effectively directing information campaigns.
The aim of our study is to investigate the influenza uptake in the different risk groups. A second aim is to compare data from different sources, in this case panel data and data available from monitoring systems and to highlight the pro’s and con’s of both methods. A third aim is to find out what reasons people give as to why they have accepted or refused influenza vaccination and whether this varies among the risk groups. We also look at the distribution channels of influenza vaccination, which may provide insight into the different health care providers that are involved in administering the vaccine.
For this study, the following research questions have been formulated:
- 1.
To what extent do various risk groups in The Netherlands receive influenza vaccination?
- 2.
What reasons do people have for accepting or refraining from an influenza vaccination and does this vary among the risk groups?
- 3.
What distribution channels are used and what is their relative share in total influenza vaccination in The Netherlands?
Special attention will be given to the risk group due to disease that is under 65 years of age. There is no information available in the literature on vaccination uptake within this group.
Section snippets
Methods
Data on vaccination uptake are available from various sources in The Netherlands.
Firstly, a mail questionnaire was sent to two existing panels that answer questions on health issues on a regular basis for Netherlands Institute of Health Services Research (NIVEL). The questionnaire contained nine questions about influenza vaccination (see Appendix A), as well as questions about the effects of influenza on sick leave used in another study. The data collection took place in May 2002 and concerned
Representativeness
Before comparing the datasources, we will investigate the representativeness of the panel data. The panel is representative of the Dutch population from the point of view of gender. There is a slight over-representation of the elderly (65 years or older) (see Table 1).
The distribution over the several categories of risk groups and non-risk groups is comparable between the panel and LINH (see Table 2).
In the panel data, there appears to be an under-representation of persons with diabetes
Conclusion and discussion
In The Netherlands, there are several sources of information on influenza vaccination uptake. The most reliable is LINH, since these data are based on recording real vaccination uptake. However, survey data have similar results. The panel-based survey of vaccination uptake seems to provide quite a reliable means of identifying uptake rates, although this requires some qualification. For the individual high-risk groups, the size and uptake rates were comparable with other national data sources.
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