Using Previous Health Behavior to Tailor Incentives

Last registered on August 04, 2025
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Pre-Trial

Trial Information

General Information

Title
Using Previous Health Behavior to Tailor Incentives
RCT ID
AEARCTR-0015334
Initial registration date
August 01, 2025

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 04, 2025, 6:08 AM EDT

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

Last updated
August 04, 2025, 5:29 PM EDT

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

Locations

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Primary Investigator

Name
Christina Brown
Affiliation
University of Chicago
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Other Primary Investigator(s)

PI Name
Rachel Glennerster
PI Affiliation
University of Chicago
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PI Name
Maryiam Haroon
PI Affiliation
University of Chicago
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PI Name
Subhash Chandir
PI Affiliation
Grassroots Health, Education, and Development Initiative
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PI Name
Mubarak Taighoon Shah
PI Affiliation
Grassroots Health, Education, and Development Initiative
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PI Name
Danya Arif Siddiqi
PI Affiliation
Grassroots Health, Education, and Development Initiative
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Additional Trial Information

Status
On going
Start date
2023-10-02
End date
2027-05-01
Keywords
Health
Additional Keywords
vaccinations
JEL code(s)
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
Our study leverages an at-scale incentive for immunization program in Pakistan to understand whether it is possible to use prior behavior or self-selection, to identify who will benefit from commitment versus who will be harmed. If healthcare providers can tailor their incentives (allowing for a longer completion window, for certain individuals versus stricter deadlines for others), this could potentially have large benefits for timely vaccination. To test this, we have partnered with IRD, an NGO in Pakistan, to compare the effect of providing payments for immunization completion with or without a deadline, and, crucially, test whether we can isolate which types of individuals benefit or are harmed by deadlines. Households currently receive a payment of 275 PKR for each of six vaccination visits, the real value of which has eroded sharply with inflation. To understand the most cost-effective way to top up the existing payments, households will be randomly assigned to the status quo or one of three treatment conditions: parents will receive a payment of 500 PKR ($1.8 USD) each time their child receives an immunization: i). within a week of age-eligibility (short deadline) ii). within a month of age eligibility (long deadline) or iii). at any point before age 2 (no deadline).
External Link(s)

Registration Citation

Citation
Arif Siddiqi, Danya et al. 2025. "Using Previous Health Behavior to Tailor Incentives." AEA RCT Registry. August 04. https://doi.org/10.1257/rct.15334-1.1
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
Households in Pakistan were randomly assigned to receive 500 PKR per vaccination under one of three conditions: (i) a short deadline—payment if the vaccine is received within one week of age eligibility, (ii) a long deadline—within one month of eligibility, or (iii) no deadline—anytime before age two.
Intervention Start Date
2024-01-01
Intervention End Date
2026-09-01

Primary Outcomes

Primary Outcomes (end points)
The main child-level immunization outcomes will be measured across a pooled regression for the six vaccines, focusing on:
(i) whether the child received the vaccine by age 2;
(ii) the number of days late after becoming age-eligible;
(iii) the delay weighted by age-specific morbidity risk; and (
iv) timeliness, defined as receiving the vaccine within two months of eligibility.

The primary outcome of interest will be (iii). This will aid in identifying whether the incentive improved timely vaccine receipt within the eligibility window or, conversely, if missing the initial deadline delayed vaccination further.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
The secondary outcomes of this study will investigate whether individuals attempted to receive the vaccine, as reported through survey responses, along with their reasons for not doing so. Additionally, the study will evaluate participants’ responses to treatment by assessing their adherence to one of three assigned vaccination deadlines—one week, one month, or by age two—as well as the timeliness of vaccination, measured by the number of days before or after their assigned deadline that they received the vaccine.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The Expanded Program on Immunization by the government of Sindh introduced a 275 PKR mobile conditional cash transfer program with no deadline (under the age of 2) for six primary incentivised vaccines. Study participants were additionally randomized at the household level to one of four conditions:
-Control: Status quo
- Treatment group 1: Payment with no deadline, where caregivers receive 500 PKR when the child receives the vaccine.
- Treatment group 2: Payment with short deadline, where caregivers receive 500 PKR if the child receives the vaccine within one week of the eligible date set by the vaccinator.
- Treatment group 3: Payment with long deadline, where caregivers receive 500 PKR if the child receives the vaccine within one month of the eligible date set by the vaccinator.
The treatment is allocated at the household level, but the incentive is provided for each child for incentivized vaccines.
Experimental Design Details
Not available
Randomization Method
Randomization done on stata
Randomization Unit
The treatment was assigned at the household level
Was the treatment clustered?
Yes

Experiment Characteristics

Sample size: planned number of clusters
4,200 households
Sample size: planned number of observations
15,400 vaccination events
Sample size (or number of clusters) by treatment arms
Control - 1,030 children
Short Deadline - 1,165 children
Long Deadline - 1,088 children
No Deadline - 1,017 children
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Simulating our main equation using DHS and pilot data, with our previous estimate of 4,200 households (and 15,400 vaccination events), we can detect main effects of 2.5 days (0.07sd) and heterogeneous treatment effects of 4.8 days (0.13-0.14sd) for our primary outcomes (alpha = 0.05, beta =0.8).
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
University of Chicago Social and Behavioral Science Institutional Review Board
IRB Approval Date
2021-10-14
IRB Approval Number
IRB21-1503
Analysis Plan

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