Testing SMS interventions to increase COVID-19 vaccination completion in Kenya

Last registered on August 22, 2023

View Trial History

Pre-Trial

Trial Information

General Information

Title

Testing SMS interventions to increase COVID-19 vaccination completion in Kenya

RCT ID

AEARCTR-0009930

Initial registration date

August 15, 2022

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published

August 18, 2022, 3:22 PM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated

August 22, 2023, 11:26 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.

Locations

Country

Kenya

Region

Kisumu

Primary Investigator

Name

Kevin Carney

Affiliation

University of Michigan

Contact Primary Investigator

Other Primary Investigator(s)

PI Name

Elisa Maffioli

PI Affiliation

The University of Michigan

Contact Investigator

PI Name

Leah Rosenzweig

PI Affiliation

The University of Chicago

Contact Investigator

PI Name

Wendy Wong

PI Affiliation

The University of Chicago

Contact Investigator

Additional Trial Information

Status

Completed

Start date

2022-07-22

End date

2023-02-15

Keywords

Health

Additional Keywords

JEL code(s)

Secondary IDs

Prior work

This trial does not extend or rely on any prior RCTs.

Abstract

This study tests SMS messages designed to increase completion rates among people who received a first but not second dose of the COVID-19 vaccine. Partnering with the Kisumu County Department of Health, four experiments were conducted to test a series of SMS- based interventions aimed at encouraging participants who had already been vaccinated for COVID-19 once to complete their vaccination regimen. The first experiment focuses on messages related to different reasons to get vaccinated. The subsequent experiments tests different deadlines to get the vaccine and obtain an airtime benefit for doing so.

External Link(s)

Registration Citation

Citation

Carney, Kevin et al. 2023. "Testing SMS interventions to increase COVID-19 vaccination completion in Kenya." AEA RCT Registry. August 22. https://doi.org/10.1257/rct.9930-2.0

Sponsors & Partners

Experimental Details

Interventions

Intervention(s)

Experiment 1 Messages: Framing the Benefits of Getting Vaccinated
1. Control: No message
2. Reminder: Reminder from Kisumu MOH to finish your COVID-19 vaccination.
3. Reminder + info: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Reply 1 (no cost) for more info.
4. Reserved for you: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Your 2nd jab has been reserved for you. Reply 1 (no cost) for more info.
5. COVID side effects: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Mild side effects are normal & mean you are building protection. Reply 1 (no cost) for more info.
6. Duty: Reminder from Kisumu MOH to finish your COVID-19 vaccination. It’s our duty to protect each other. Vaccination is part of that. Reply 1 (no cost) for more info.
7. COVID still a threat: Reminder from Kisumu MOH to finish your COVID-19 vaccination. COVID-19 is still out there. Get your 2nd jab today! Reply 1 (no cost) for more info.
8. Time-limited reimbursement - deadline of one week: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Get your 2nd jab in the next week and receive 100/= airtime! Reply 1 (no cost) for more info.

Experiment 2 Messages: Optimizing the Timing of Vaccination Benefits
1. Control: No message
2. Reminder: Reminder from Kisumu MOH to finish your COVID-19 vaccination.
3. Reminder + info: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Reply 1 (no cost) for more info.
4. Time-limited reimbursement - deadline of current day: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Get your 2nd jab today and receive 100/= airtime! Reply 1 (no cost) for more info.
5. Time-limited reimbursement - deadline of one week: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Get your 2nd jab in the next week and receive 100/= airtime! Reply 1 (no cost) for more info.
6. No limit reimbursement (with reimbursement valid for one month): Reminder from Kisumu MOH to finish your COVID-19 vaccination. Get your 2nd jab and receive 100/= airtime! Reply 1 (no cost) for more info.
7. Scarcity: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Hurry! The next 100 to get a 2nd jab receive 100/= airtime. Reply 1 (no cost) for more info.

Experiment 3 and 4 Messages: Optimizing the Timing of Vaccination Benefits
1. Control: No message
2. Reminder: Reminder from Kisumu MOH to finish your COVID-19 vaccination.
3. Reminder + info: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Reply 1 (no cost) for more info.
4. Time-limited reimbursement - deadline of current day: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Get your 2nd jab today and receive 100/= airtime! Reply 1 (no cost) for more info.
5. Time-limited reimbursement - deadline of one week: Reminder from Kisumu MOH to finish your COVID-19 vaccination. Get your 2nd jab in the next week and receive 100/= airtime! Reply 1 (no cost) for more info.

Upon replying 1, respondents receive an SMS stating: Your 2nd vaccine dose reduces your risk of getting COVID-19 & severe illness. Available for free at most health facilities. Full facilities list: [tracked link to facilities]

Where airtime is offered, upon replying 1, respondents will also receive an SMS stating: 100/= airtime will be sent to your phone if you reply here with the facility name and date where you got your 2nd jab. Offer not transferable.

Intervention Start Date

2022-07-22

Intervention End Date

2023-01-30

Primary Outcomes

Primary Outcomes (end points)

Rates of completion of the full, two-dose vaccination course. Vaccination completion rates will be measured at several points in time using administrative data from the Kisumu County Department of Health. The primary outcome will be the rate of full (two-dose) vaccination. The speed of second-dose completion will also be analyzed.

Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)

To supplement the administrative vaccination records, the SMS system will also collect data on people’s engagement with (responses to) the intervention messages.

The first outcome to analyze is the rate at which participants reply “1” in each of the conditions where they are invited to do so. The second outcome is the rate at which participants click the link they are provided upon replying “1,” measured using an individualized link for each treatment condition. The final outcome is the response rate in the airtime conditions when people are asked to reply with their vaccination date and location.

Secondary Outcomes (explanation)

Experimental Design

This study involves the 29,474 people in three subcounties of Kisumu County who had received a first, but not second, dose of the COVID-19 vaccine as of July 17, 2022. The subcounties included in the study are Kisumu Central, Kisumu West, and Nyakach. These particular subcounties were chosen to exclude locations where the Kisumu County Department of Health already had other COVID-19 experiments ongoing in partnership with our research team.

The two experiments described above were scheduled to occur approximately one week apart. Half of the individuals were randomized to the first experiment, and half to the second. Within each experiment, individuals were randomized in equal proportions into the eight treatment conditions listed above (seven messages and one control group). Each individual within a trial received the message assigned to them at the same time, and received any relevant follow-up messages immediately upon replying “1”. This is the extent of the interventions.

Experimental Design Details

Randomization Method

Randomization occurred at the individual level and was stratified on observables in the vaccination database: gender, age (using an indicator for being above age 35), and subcounty where the first vaccination dose occurred. The randomization process occurred in an office on a computer.

Randomization Unit

Individual

Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters

N/A

Sample size: planned number of observations

26,755

Sample size (or number of clusters) by treatment arms

Experiment 1
1. Control: 1,834
2. Baseline reminder: 1,842
3. Baseline reminder + info: 1,846
4. Reserved for you: 1,842
5. Covid side effects: 1,842
6. Duty: 1,843
7. Covid is still a threat: 1,841
8. Airtime (1 week deadline): 1,846

Experiment 2
1. Control: 1,710
2. Baseline reminder: 1,716
3. Baseline reminder + info: 1,719
4. Time-limited reimbursement - deadline of current day: 1,716
5. Time-limited reimbursement - deadline of one week: 1,719
6. No limit reimbursement (with reimbursement valid for one month): 1,716
7. Scarcity: 1,726

Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

In experiment 1, the study is able to detect a difference in vaccination rates of at least 3.45 percentage points between any two treatments, assuming a 15% vaccination rate in the control group. In experiment 2, the study is able to detect a difference in vaccination rates of at least 3.58 percentage points between any two treatments, assuming a 15% vaccination rate in the control group.

Supporting Documents and Materials

IRB