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Field
Abstract
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Before
This study investigates the relationship between influenza immunization and worker productivity. We conducted a natural field experiment among food delivery drivers in China, varying the incentives for vaccination by offering it either at a 50% discount or free of charge. The study includes 600 drivers, from whom we collected basic demographic information such as gender, age, and education level. Worker productivity is assessed using four indicators: order volume, on-time rate, average delivery duration, and the number of positive customer reviews.
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After
This study evaluates the impact of financial incentives on influenza vaccination uptake and explores whether vaccination improves health outcomes and, in turn, worker productivity. We conduct a randomized controlled field experiment with approximately 750 food delivery drivers in China. The experiment has two main components. First, we examine the causal impact of financial incentives on vaccine uptake by providing influenza vaccine subsidies covering 50% and 100% of the average vaccine cost, using a control group that receives no subsidy. We then track participants’ vaccination decisions and key productivity outcomes, including order volume, on-time delivery rate, average delivery duration, and the number of positive customer reviews. Second, we study the role of peer influence in vaccination behavior by observing how the vaccination choices of vaccinated food delivery drivers affect the vaccination decisions of other participants. The findings will shed light on how financial incentives and the behavior of peers jointly shape health behavior and productivity in a high-frequency labor market setting.
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Field
Last Published
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Before
September 15, 2025 09:54 AM
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After
October 13, 2025 09:22 AM
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Field
Intervention (Public)
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Before
Our intervention includes offering the vaccine either at a 50% discount or free of charge to food delivery drivers.
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After
This research aims at studying the impact of financial incentives on the take-up willingness of influenza vaccine. Moreover, the researchers examine the relationship between influenza vaccine and health outcomes. If health is improved after taking the vaccine, do we observe an increase in the worker productivity as well. Meanwhile, the researchers quantify the peer influence in the willingness to take the vaccination. Our first intervention includes a financial incentive on vaccine uptake by providing influenza vaccine subsidies covering 50% and 100% of the average vaccine cost, using a control group that receives no subsidy. Our second intevention is the information diffusion where we randomize participants into peer-on and peer-off groups where the peer-on group receives information of the vaccination decision of their vaccinated peers every two days (SMS messages).
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Field
Intervention Start Date
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November 15, 2025
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October 15, 2025
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Intervention End Date
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February 15, 2026
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March 15, 2026
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Field
Primary Outcomes (End Points)
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Before
1. The self-reported health (mental, physical health) 2. worker productivity of food delivery drivers (volumes of order, duration, reviews)
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After
1. take up the influenza vaccination or not 2.The self-reported health (mental, physical health) 3. worker productivity of food delivery drivers (volumes of order, duration, reviews)
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Field
Experimental Design (Public)
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Before
We conducted a randomized controlled trial to examine the impact of influenza immunization on the productivity of food delivery drivers in China. A total of 600 drivers were recruited to participate in the study. After collecting baseline demographic information, including gender, age, and education level, drivers were randomly assigned into one of three groups:
Control group – no incentive for vaccination.
Treatment group 1 – offered influenza vaccination at a 50% discount.
Treatment group 2 – offered influenza vaccination free of charge.
This random assignment ensures that differences in outcomes can be attributed to the vaccination incentives rather than pre-existing characteristics. Productivity outcomes were measured over the study period using four indicators: Order volume (number of completed deliveries), On-time rate (share of deliveries completed on schedule), Average delivery duration, and Number of positive customer reviews.
By comparing productivity across groups, we assess whether vaccination incentives influence both vaccine uptake and subsequent worker productivity.
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After
We conducted a randomized controlled trial to examine the impact of influenza vaccination on vaccine uptake and worker productivity among food delivery drivers in China. In addition, we quantify the peer influence associated with vaccination behavior. Approximately 750 drivers were recruited for the study. After collecting baseline demographic and socioeconomic information—including gender, age, education, marital status, wage, job experience, working hours, health status, medical history, health behavior, and health insurance coverage—participants were randomly assigned to one of three treatment groups or a control group across two rounds of vaccination.
The field experiment consisted of four groups in total: one control group and three treatment groups. Participants in the control group received no financial incentive for vaccination and no information about the vaccination status of their peers. The first treatment group received a low financial incentive, offering participants a 50% discount on the average vaccination cost, without any group information. The second treatment group received a high financial incentive, offering a 100% subsidy of the average vaccine cost. The third treatment group received peer information only—participants were informed of other drivers’ vaccination outcomes but received no financial incentive. Comparing vaccination uptake between the peer-information group and the control group allows us to identify the role of social influence in vaccination decisions. Random assignment ensures that any observed differences in outcomes can be attributed to the vaccination incentives rather than to pre-existing individual characteristics.
Worker productivity was tracked throughout the study period using four key performance indicators: (1) order volume (total number of completed deliveries), (2) on-time delivery rate (percentage of orders delivered as scheduled), (3) average delivery duration, and (4) number of positive customer reviews. By comparing productivity outcomes across the four groups, we evaluate whether vaccination incentives affect not only vaccine uptake but also subsequent work performance.
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Field
Randomization Unit
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Before
prefecture level for some treatment, and individual randomization for some treatments
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Individual randomization
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Planned Number of Clusters
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600 food delivery drivers
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750 food delivery drivers
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Sample size (or number of clusters) by treatment arms
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300 in treatment group and 300 in control group
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After
200 in high and low financial incentive treatment, 200 in control groups. The remaining 150 in peer-on group.
Around 750 clusters.
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Field
Power calculation: Minimum Detectable Effect Size for Main Outcomes
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Individual clustering
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