The goal of this project is to see if encouraging an individual to privately choose in advance a narrow time window in which to obtain a flu vaccination shot affects the likelihood that he or she will become vaccinated.

Influenza causes 36,000 U.S. deaths per year, but influenza immunization rates average just 28%. Behavioral "nudges" may increase the effectiveness of immunization reminder mailers at little or no added cost. Past psychology research has demonstrated that prompting people to form an implementation plan of the form, "When situation x arises, I will implement response y," increases attainment of desired goals because the desired behavior is linked to a concrete future moment. We study whether adding a planning prompt to a vaccination reminder mailer increases immunization rates.

Inclusion Criteria:

• seasonal influenza vaccine indications according to the CDC
• employees of partner corporations executing study

Exclusion Criteria:

• none