Determinants of influenza vaccination timing.

New guidelines recommend different influenza vaccination timing for different subpopulations due to the limited availability of flu shots (FS). This study's objectives are to develop a theoretical model to demonstrate why some individuals choose to receive an early FS while others choose a late FS and to empirically explore the determinants of vaccination timing. Empirical results generally supported the theoretical results. Individuals vary their FS timing in response to variations in perceived risks, chronic condition levels reflecting their risk of influenza infection, and opportunity costs, measured by the presence of medical care other than an FS. (c) 2005 John Wiley & Sons, Ltd.