Research on influenza vaccine uptake has focused largely on intrapersonal determinants (perceived risk, past vaccine acceptance, perceived vaccine safety) and on physician recommendation. The authors used a social ecological framework to examine influenza vaccine uptake during the 2009 H1N1 pandemic. Surveying an adult population (n = 2,079) in January 2010 with significant oversamples of Blacks and Hispanics, this study found that 18.4% (95% confidence interval = 15.6-21.5) had gotten the 2009 H1N1 vaccine. Variables at each level of the social ecological model were significant predictors of uptake as well as of intent to get the vaccine. The intrapersonal level explained 53%, the interpersonal explained 47%, the institutional level explained 34%, and the policy and community levels each explained 8% of the variance associated with vaccine uptake. The levels together explained 65% of the variance, suggesting that interventions targeting multiple levels of the framework would be more effective than interventions aimed at a single level. (Contains 6 tables and 1 figure.)