It is unknown whether a first influenza vaccination protects high-risk adults from severe morbidity and mortality during influenza epidemics. As part of the PRISMA nested case-control study, we aimed to evaluate the effectiveness of first-time and repeat influenza vaccinations in adult persons recommended for vaccination aged between 18 and 64 years during the 1999-2000 influenza A epidemic. After adjustments, 69% of hospitalizations for acute respiratory or cardiovascular disease or death were prevented in first-time vaccinees (95% percent confidence interval [95% CI]: 8-90%). The corresponding figure in persons who were vaccinated before was 85% (95% CI: 36-96%). Adult persons with high-risk medical conditions can substantially benefit from a first and repeat influenza vaccination prior to an epidemic.
Bibliographical noteFunding Information:
We thank all GPs who participated in this study. We also thank Mrs. S. van Loon, Mrs. H. den Breeijen, Mrs. N. Boekema-Bakker and Mrs. M. Haak for data-management. Funding/support : This study was supported by The Netherlands Health Care Insurance Board. The Netherlands Health Care Insurance Board directly subsidizes The Netherlands Program on Influenza. From 1997 to 2003 influenza vaccines were bought centrally from pharmaceutical industries and distributed by the National Society for Health Promotion and the Environment. Since no financial profits could be made by either organisation, there is no conflict of interest. The design, analysis and interpretation of the study was conducted independently of The Netherlands Health Care Insurance Board. Conflict of interest : None declared.
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