SUMMARYTo increase uptake of flu vaccines and maintain a healthy workforce during the 2016-17 flu season, New York City’s Behavioral Design Team (NYC BDT) partnered with WorkWell NYC to design behaviorally informed emails to encourage New York City employees to visit a worksite flu clinic. One version of the redesigned email used the strategy of “enhanced active choice,” whereby employees were prompted to make a choice that had a clear right answer.IMPACTBehavioral emails more than doubled click-through rates and statistically increased appointment sign-ups. Most importantly, the enhanced active choice version of the email increased vaccine uptake by 5 percent at worksite locations.