Influenza, Human
Conditions
Keywords
Influenza vaccination, behavioral science interventions, vaccination promotion
Brief summary
This research aims to identify which behavioral science strategies are most effective at increasing flu vaccination rates overall and based on patients' individual characteristics. Past behavioral science interventions have shown promise in increasing flu vaccinations. For example, successful interventions have encouraged people to make concrete plans for when they will get a flu vaccination (Milkman et al. 2011), sent automated calls or text messages reminding patients to get a flu vaccination (Cutrona et al. 2018; Regan et al. 2017), or provided financial incentives for getting vaccinated (Nowalk et al. 2010). Although these results are promising, these studies have been conducted in isolation on different populations, which makes it difficult to compare their interventions' effectiveness or to have enough power to reliably detect differing responses to interventions based on individual characteristics. This research will simultaneously test 19 different SMS interventions to increase flu vaccinations in a mega-study and apply machine learning to identify which interventions work best for whom. The interventions are designed by behavioral science experts from the Behavior Change for Good Initiative (BCFG), Penn Medicine Nudge Unit (PMNU), and Geisinger Behavioral Insights Team (BIT). We expect to include at least 80,000 participants. The specific aims of this research are to identify (1) which behavioral science strategies effectively increase flu vaccination rates overall, and (2) which strategies are most effective for different subgroups (e.g., based on age, gender, race).
Interventions
BEHAVIORALFlu shot text messages
Participants will receive text messages per descriptions listed in the arms.
Sponsors
Geisinger Clinic
University of Pennsylvania
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
HEALTH_SERVICES_RESEARCH
Masking
DOUBLE (Caregiver, Outcomes Assessor)
Masking description
As treated participants will receive text messages, there is no scope for blinding. Care providers will not be made aware of subjects' participation in the study, or assigned treatment arms. The study team will only receive data on subjects' assigned arms at the end of the study.
Intervention model description
Participants will be randomly assigned to the different arms. Randomization will be stratified by age (65+ vs. 18-64), vaccine receipt in 2019-2020 flu season (yes vs. no/unknown), and study site (Penn Medicine vs. Geisinger).
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Penn Medicine and Geisinger patients will be included if they: Inclusion Criteria: * Have a cell phone number recorded in a Penn Medicine or Geisinger database * Have a new or routine primary care appointment during the study recruitment period (not a sick visit)
Exclusion criteria
* Have documentation of allergy or adverse event to influenza vaccination in medical records * Have documentation of already receiving their 2020 influenza vaccination prior to randomization in medical records * Have opted out of receiving text message appointment reminders * Have asked not to be contacted for research purposes * Have an appointment with someone other than their primary care physician * Have an appointment with someone other than a physician, resident, nurse practitioner, or physician assistant We will recruit as many patients as possible starting in September 2020. We will stop enrolling participants with appointments scheduled to occur after December 31, 2020 if we have reached 4,000 participants per condition. If we do not have 4,000 participants per condition by December 31, 2020, we will continue enrolling participants until we have reached 4,000 per condition, or until March 31, 2021 (discontinuing enrollment at whichever milestone arrives sooner - 4,000 people enrolled or 3/31/21).
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Number of Participants With Flu Shot Receipt at or Before Appointment | The dependent variable will be assessed during a 4-day period after randomization starting three days prior to the participant's target primary care appointment through the date of the target appointment (including the date of the appointment) | Our field experiment will be conducted with Penn Medicine and Geisinger Health patients via SMS messages sent prior to their first primary care appointment during the study period, hereafter referred to as the target appointment. The key dependent variable is whether participants receive a flu shot at or before their target appointment (as recorded in their electronic health records). If participants cancel or do not show up for their target appointment after they have been randomized to a treatment and then schedule a new appointment during the study period, their new primary care appointment becomes the target appointment. Participants who have been randomized to a treatment will be counted as not having received a flu shot if they cancel or do not show up for their target appointment and do not schedule a new appointment during the study period. Participants who receive a flu shot before they receive the SMS intervention will be excluded from the analyses. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Number of Participants With Flu Shot Receipt Before March 31, 2021 | Up to 6 months after randomization. | The secondary dependent variable is whether participants receive the flu shot at or before their target appointment or at any time after this appointment (by March 31, 2021), as recorded in their electronic health records. Participants who receive a flu shot before they receive the SMS intervention will be excluded from the analyses. |
Countries
United States
Participant flow
Pre-assignment details
A small number of patients in each experimental condition did not receive any intervention messages due to technical malfunctions. These patients are excluded from analyses since they were, for all practical purposes, not a part of of our study
Participants by arm
| Arm | Count |
|---|---|
| Holdout Control Participants will only receive the standard appointment reminders from their providers. | 3,742 |
| Default Reservations Opt-Out Condition The day before their scheduled appointment, participants receive a text reading: A flu shot has been reserved for you to receive at your appointment tomorrow. Reply Y if you want this shot held for you, N if you don't. The text will include a picture of a vial that says Your Flu Shot on it.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,737 |
| Default Reservations Opt-In Condition The day before their scheduled appointment, participants receive a text reading: Reply Y if you would like to receive a flu shot at your appointment tomorrow, N if not. The text will include a picture of vial with no text on it.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,709 |
| Intergroup Competition Treatment Condition Three days before their scheduled appointment, participants will receive a text message with information about how much your region lagged behind another region in flu shot rate last year (your region and another region will depend on the study site and include realistic flu shot rates based on historical CDC data). Participants will receive a reminder message on the day of the appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,735 |
| Intergroup Competition Control Condition Three days before their scheduled appointment, participants will receive a text message with information about how much your region lagged behind the target flu shot rate of 70% last year (your region will depend on the study site and include realistic flu shot rates based on historical CDC data). Participants will receive a reminder message on the day of the appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,758 |
| Flu Shot for You Symbolic Condition Three days before their scheduled appointment, participants will receive a text message encouraging them to get a flu shot. They will also be told that they have the opportunity to dedicate getting the flu shot to someone by texting back the initials of an individual. Participants will receive a reminder message on the day of the appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,769 |
| Flu Shot for You Herd Immunity Condition Three days before their scheduled appointment, participants will receive a text message encouraging them to get a flu shot. They will also be told that they have the opportunity of getting the flu shot to protect a vulnerable loved one by texting back the initials of an individual. Participants will receive a reminder message on the day of the appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,719 |
| Flu Shot for You Control Condition Three days before their scheduled appointment, participants will receive a text message encouraging them to get a flu shot. They will also receive a reminder message on the day of the appointment. They will not receive any further information, nor will they be asked to respond with initials of an individual.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,732 |
| Prosocial Condition The day before their scheduled appointment, participants will receive a message describing the pro-social benefits of getting a flu shot, and a reminder to ask for their flu shot. The described pro-social benefits will vary whether they emphasize the COVID-19 pandemic (e.g., protecting loved ones from the risk of hospital-acquired COVID-19 infection) or not (e.g., protecting loved ones from serious complications from the flu). Participants will also receive a reminder message on the day of the appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,728 |
| Self-Oriented Condition The day before their scheduled appointment, participants will receive a message describing the self-oriented benefits of getting a flu shot, and a reminder to ask for their flu shot. The described self-oriented benefits will vary whether they emphasize the COVID-19 pandemic (e.g., protecting oneself from the risk of hospital-acquired COVID-19 infection) or not (e.g., protecting oneself from serious complications from the flu).
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,777 |
| Information Vivid Condition Three days before their scheduled appointment, participants will receive a message inviting them to watch a 2-minute wellness video and answer some related questions, as well as encouragement to get the flu shot. In this condition, the video will contain vivid information about getting the flu. Participants will also receive a reminder message the day before the appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,672 |
| Information Basic Condition Three days before their scheduled appointment, participants will receive a message inviting them to watch a 2-minute wellness video and answer some related questions, as well as encouragement to get the flu shot. In this condition, the video will contain basic information about getting the flu. Participants will also receive a reminder message the day before the appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,751 |
| Information Control Condition Three days before their scheduled appointment, participants will receive a message inviting them to watch a 2-minute wellness video and answer some related questions, as well as encouragement to get the flu shot. In this condition, the video will contain information about exercising. Participants will also receive a reminder message the day before the appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,737 |
| Sharing Humor Condition The day before their scheduled appointment, participants will receive a text message encouraging them to get the flu shot. The message will include a joke about the flu and will encourage participants to share the joke with nurses, doctors, or pharmacists.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,714 |
| No Humor Condition The day before their scheduled appointment, participants will receive a text message encouraging them to get the flu shot.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,773 |
| Healthy Habits Easy Health Behavior Condition The day before their scheduled appointment, participants will be asked if they have completed a series of easy health behaviors (e.g., whether they walked 500 feet yesterday, at least two serving of fruits and vegetables in the last week, and slept at least 6 hours the previous night). They will then be encouraged to get a flu shot at their appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,739 |
| Healthy Habits Difficult Health Behavior Condition The day before their scheduled appointment, participants will be asked if they have completed a series of difficult health behaviors (e.g., whether they walked 3 miles yesterday, ate 4-6 servings of fruits and vegetables yesterday, and slept at least 9 hours the previous night). They will then be encouraged to get a flu shot at their appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,776 |
| Healthy Habits Control Condition The day before their scheduled appointment, participants will receive a text message encouraging them to get a flu shot.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,744 |
| Just-In-Time Reminders 24-Hour Condition Seventy-two hours before their appointment, participants will receive a text message alerting them to the availability of the flu vaccine at their upcoming appointment. Participants will be told they'll receive a reminder, which they can opt-out from receiving. The text message reminder will be sent 24 hours before their appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,741 |
| Just-In-Time Reminders 15-Minute Condition Just-In-Time Reminders 15-Minute Condition: Seventy-two hours before their appointment, participants will receive a text message alerting them to the availability of the flu vaccine at their upcoming appointment. Participants will be told they'll receive a reminder, which they can opt-out from receiving. The text message reminder will be sent 15 minutes before their appointment.
Flu shot text messages: Participants will receive text messages per descriptions listed in the arms. | 3,758 |
| Total | 74,811 |
Baseline characteristics
| Characteristic | Default Reservations Opt-Out Condition | Default Reservations Opt-In Condition | Intergroup Competition Treatment Condition | Intergroup Competition Control Condition | Flu Shot for You Symbolic Condition | Flu Shot for You Herd Immunity Condition | Flu Shot for You Control Condition | Prosocial Condition | Self-Oriented Condition | Information Vivid Condition | Holdout Control | Information Basic Condition | Information Control Condition | Sharing Humor Condition | No Humor Condition | Healthy Habits Easy Health Behavior Condition | Healthy Habits Difficult Health Behavior Condition | Healthy Habits Control Condition | Just-In-Time Reminders 24-Hour Condition | Just-In-Time Reminders 15-Minute Condition | Total |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Age, Categorical <=18 years | 24 Participants | 21 Participants | 20 Participants | 31 Participants | 21 Participants | 21 Participants | 15 Participants | 24 Participants | 24 Participants | 22 Participants | 22 Participants | 31 Participants | 24 Participants | 14 Participants | 24 Participants | 19 Participants | 16 Participants | 19 Participants | 20 Participants | 28 Participants | 440 Participants |
| Age, Categorical >=65 years | 793 Participants | 767 Participants | 775 Participants | 785 Participants | 807 Participants | 782 Participants | 794 Participants | 772 Participants | 798 Participants | 748 Participants | 770 Participants | 772 Participants | 752 Participants | 750 Participants | 807 Participants | 793 Participants | 804 Participants | 793 Participants | 774 Participants | 771 Participants | 15607 Participants |
| Age, Categorical Between 18 and 65 years | 2920 Participants | 2921 Participants | 2940 Participants | 2942 Participants | 2941 Participants | 2916 Participants | 2923 Participants | 2932 Participants | 2955 Participants | 2902 Participants | 2950 Participants | 2948 Participants | 2961 Participants | 2950 Participants | 2942 Participants | 2927 Participants | 2956 Participants | 2932 Participants | 2947 Participants | 2959 Participants | 58764 Participants |
| Age, Continuous | 50.7 years STANDARD_DEVIATION 16.4 | 50.5 years STANDARD_DEVIATION 16.3 | 50.7 years STANDARD_DEVIATION 16.2 | 50.5 years STANDARD_DEVIATION 16.2 | 50.9 years STANDARD_DEVIATION 16.3 | 50.5 years STANDARD_DEVIATION 16.4 | 50.8 years STANDARD_DEVIATION 16.6 | 50.9 years STANDARD_DEVIATION 16.2 | 50.6 years STANDARD_DEVIATION 16.2 | 50.8 years STANDARD_DEVIATION 16.1 | 50.3 years STANDARD_DEVIATION 16.2 | 50.8 years STANDARD_DEVIATION 16.1 | 50.7 years STANDARD_DEVIATION 16.1 | 50.5 years STANDARD_DEVIATION 16.2 | 50.9 years STANDARD_DEVIATION 16.3 | 51.0 years STANDARD_DEVIATION 16.3 | 51.0 years STANDARD_DEVIATION 16 | 50.7 years STANDARD_DEVIATION 16.3 | 50.7 years STANDARD_DEVIATION 16.2 | 50.5 years STANDARD_DEVIATION 16 | 50.7 years STANDARD_DEVIATION 16.2 |
| Race/Ethnicity, Customized Race category Asian | 82 Participants | 91 Participants | 99 Participants | 86 Participants | 75 Participants | 87 Participants | 88 Participants | 93 Participants | 83 Participants | 90 Participants | 86 Participants | 91 Participants | 87 Participants | 88 Participants | 93 Participants | 84 Participants | 80 Participants | 89 Participants | 85 Participants | 77 Participants | 1734 Participants |
| Race/Ethnicity, Customized Race category Black | 729 Participants | 736 Participants | 688 Participants | 730 Participants | 717 Participants | 711 Participants | 705 Participants | 719 Participants | 755 Participants | 676 Participants | 751 Participants | 667 Participants | 713 Participants | 673 Participants | 741 Participants | 676 Participants | 722 Participants | 714 Participants | 698 Participants | 701 Participants | 14222 Participants |
| Race/Ethnicity, Customized Race category Hispanic | 177 Participants | 173 Participants | 168 Participants | 157 Participants | 180 Participants | 156 Participants | 174 Participants | 174 Participants | 177 Participants | 181 Participants | 187 Participants | 143 Participants | 177 Participants | 183 Participants | 154 Participants | 160 Participants | 162 Participants | 175 Participants | 145 Participants | 188 Participants | 3391 Participants |
| Race/Ethnicity, Customized Race category Other | 114 Participants | 149 Participants | 126 Participants | 134 Participants | 147 Participants | 130 Participants | 116 Participants | 140 Participants | 108 Participants | 139 Participants | 140 Participants | 128 Participants | 144 Participants | 131 Participants | 128 Participants | 135 Participants | 113 Participants | 144 Participants | 134 Participants | 138 Participants | 2638 Participants |
| Race/Ethnicity, Customized Race category White | 2635 Participants | 2560 Participants | 2654 Participants | 2651 Participants | 2650 Participants | 2635 Participants | 2649 Participants | 2602 Participants | 2654 Participants | 2586 Participants | 2578 Participants | 2722 Participants | 2616 Participants | 2639 Participants | 2657 Participants | 2684 Participants | 2699 Participants | 2622 Participants | 2679 Participants | 2654 Participants | 52826 Participants |
| Sex: Female, Male Female | 2109 Participants | 2079 Participants | 2067 Participants | 2096 Participants | 2097 Participants | 2018 Participants | 2091 Participants | 2083 Participants | 2120 Participants | 2030 Participants | 2056 Participants | 2107 Participants | 2060 Participants | 2104 Participants | 2098 Participants | 2085 Participants | 2159 Participants | 2120 Participants | 2101 Participants | 2091 Participants | 41771 Participants |
| Sex: Female, Male Male | 1628 Participants | 1630 Participants | 1668 Participants | 1662 Participants | 1672 Participants | 1701 Participants | 1641 Participants | 1645 Participants | 1657 Participants | 1642 Participants | 1686 Participants | 1644 Participants | 1677 Participants | 1610 Participants | 1675 Participants | 1654 Participants | 1617 Participants | 1624 Participants | 1640 Participants | 1667 Participants | 33040 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk | EG004 affected / at risk | EG005 affected / at risk | EG006 affected / at risk | EG007 affected / at risk | EG008 affected / at risk | EG009 affected / at risk | EG010 affected / at risk | EG011 affected / at risk | EG012 affected / at risk | EG013 affected / at risk | EG014 affected / at risk | EG015 affected / at risk | EG016 affected / at risk | EG017 affected / at risk | EG018 affected / at risk | EG019 affected / at risk |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 |
| other Total, other adverse events | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 |
| serious Total, serious adverse events | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 |
Outcome results
Primary
Number of Participants With Flu Shot Receipt at or Before Appointment
Our field experiment will be conducted with Penn Medicine and Geisinger Health patients via SMS messages sent prior to their first primary care appointment during the study period, hereafter referred to as the target appointment. The key dependent variable is whether participants receive a flu shot at or before their target appointment (as recorded in their electronic health records). If participants cancel or do not show up for their target appointment after they have been randomized to a treatment and then schedule a new appointment during the study period, their new primary care appointment becomes the target appointment. Participants who have been randomized to a treatment will be counted as not having received a flu shot if they cancel or do not show up for their target appointment and do not schedule a new appointment during the study period. Participants who receive a flu shot before they receive the SMS intervention will be excluded from the analyses.
Time frame: The dependent variable will be assessed during a 4-day period after randomization starting three days prior to the participant's target primary care appointment through the date of the target appointment (including the date of the appointment)
| Arm | Measure | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|
| Holdout Control | Number of Participants With Flu Shot Receipt at or Before Appointment | 1113 Participants |
| Default Reservations Opt-Out Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1210 Participants |
| Default Reservations Opt-In Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1150 Participants |
| Intergroup Competition Treatment Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1163 Participants |
| Intergroup Competition Control Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1183 Participants |
| Flu Shot for You Symbolic Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1200 Participants |
| Flu Shot for You Herd Immunity Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1192 Participants |
| Flu Shot for You Control Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1191 Participants |
| Prosocial Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1157 Participants |
| Self-Oriented Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1224 Participants |
| Information Vivid Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1144 Participants |
| Information Basic Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1231 Participants |
| Information Control Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1171 Participants |
| Sharing Humor Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1135 Participants |
| No Humor Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1199 Participants |
| Healthy Habits Easy Health Behavior Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1181 Participants |
| Healthy Habits Difficult Health Behavior Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1193 Participants |
| Healthy Habits Control Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1130 Participants |
| Just-In-Time Reminders 24-Hour Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1240 Participants |
| Just-In-Time Reminders 15-Minute Condition | Number of Participants With Flu Shot Receipt at or Before Appointment | 1227 Participants |
Secondary
Number of Participants With Flu Shot Receipt Before March 31, 2021
The secondary dependent variable is whether participants receive the flu shot at or before their target appointment or at any time after this appointment (by March 31, 2021), as recorded in their electronic health records. Participants who receive a flu shot before they receive the SMS intervention will be excluded from the analyses.
Time frame: Up to 6 months after randomization.
| Arm | Measure | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|
| Holdout Control | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1296 Participants |
| Default Reservations Opt-Out Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1391 Participants |
| Default Reservations Opt-In Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1330 Participants |
| Intergroup Competition Treatment Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1343 Participants |
| Intergroup Competition Control Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1338 Participants |
| Flu Shot for You Symbolic Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1371 Participants |
| Flu Shot for You Herd Immunity Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1369 Participants |
| Flu Shot for You Control Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1370 Participants |
| Prosocial Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1360 Participants |
| Self-Oriented Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1418 Participants |
| Information Vivid Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1316 Participants |
| Information Basic Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1385 Participants |
| Information Control Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1342 Participants |
| Sharing Humor Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1310 Participants |
| No Humor Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1351 Participants |
| Healthy Habits Easy Health Behavior Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1370 Participants |
| Healthy Habits Difficult Health Behavior Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1360 Participants |
| Healthy Habits Control Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1297 Participants |
| Just-In-Time Reminders 24-Hour Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1388 Participants |
| Just-In-Time Reminders 15-Minute Condition | Number of Participants With Flu Shot Receipt Before March 31, 2021 | 1388 Participants |