Way to Health

BCFG Flu Mega Study

This is a mega trial with planned enrollment of 150,000 patients across Penn Medicine and Geisinger Health system. The intent was to simultaneously test out 19 different nudges to figure out how to increase flu vaccination rates. The secondary intent was to use learnings from this to inform COVID vaccination efforts. The best performing nudge increases uptake by 11% over previous year baselines. The study was replicated with Walmart with 800,000+ participants.

Feb 24, 2021

Katherine Milkman, PhD Katherine Milkman, PhD
Mitesh Patel, MD, MBA Mitesh Patel, MD, MBA

Aim and Key Question

Many Americans fail to get life-saving vaccines each year, and the availability of a vaccine for COVID-19 makes the challenge of encouraging vaccination more urgent than ever. This program was a large field experiment (N=47,308 with recruitment still ongoing) testing 19 different nudges delivered to patients via text message and designed to boost adoption of the influenza vaccine.

Intervention and Design

Working closely with Penn Medicine and Geisinger Health System, Way to Health integrated to the respective EHRs (EPIC) to automatically enroll participants based on upcoming primary care appointments and other inclusion and exclusion criteria, namely:


The program went live on Sept 24, 2020 and recruitment is still ongoing. The initial findings are derived from data collected up to December 31, 2020. Protocols varied the contents and/or timing of up to two sets of text reminders to get a flu shot sent from the patient’s healthcare provider in the three days preceding the patient’s appointment. 19 different arms (interventions) were built and participants randomized across them.

Main Outcomes and Measures

The key metric tracked was the incremental uptake of the flu vaccine compared to last year’s baseline for each intervention / nudge.

Way to Health Use

Findings and Conclusions

Findings suggest text messages sent prior to a primary care visit can boost vaccination rates by up to 11%. Overall, interventions performed better when they were (a) framed as reminders to get flu shots that were already reserved for the patient and (b) congruent with the sort of communications patients expected to receive from their healthcare provider (i.e., not surprising, casual, or interactive). The most potent intervention reminded patients twice to get their flu shot at their upcoming doctor’s appointment and indicated it was reserved for them. This successful script could be used as a template for campaigns to encourage the adoption of life-saving vaccines, including against COVID-19.

Publications and Press

  • A Mega-Study of Text-Based Nudges Encouraging Patients to Get Vaccinated at an Upcoming Doctor’s Appointment
  • A Mega-Study of Text-Message Nudges Encouraging Patients to Get Vaccinated at their Pharmacy
  • Behavior Change for Good unveils effective strategies to boost vaccination rates