Personalized Nudging to Increase Influenza Vaccinations

Inclusion Criteria: * Age 18+ * Has not received the 2024 flu vaccine according to the Geisinger electronic health record (EHR) prior to randomization * Has a non-acute, flu-shot eligible, in-person Geisinger appointment scheduled with enough time to be randomized * Has a Geisinger primary care provider Exclusion Criteria: * Cannot be contacted by SMS (e.g., due to insufficient/missing contact information in the EHR or because they opted out) * Appointment type or department not approved for outreach by Geisinger leadership at the time of outreach * Has an allergy to flu vaccines according to any EHR allergy table known to the study team * Has a health maintenance modifier indicating they are permanently discontinued from receiving a seasonal flu shot * Shares a phone number with someone who has already been enrolled