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Information and vaccine uptake

Last registered on November 19, 2018
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Pre-Trial

Trial Information

General Information

Title
Information and vaccine uptake
RCT ID
AEARCTR-0003520
Initial registration date
November 19, 2018

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
November 19, 2018, 7:45 PM EST

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

Locations

Country
Finland
Region
Multiple

Primary Investigator

Name
Lauri Sääksvuori
Affiliation
Contact Primary Investigator

Other Primary Investigator(s)

Additional Trial Information

Status
On going
Start date
2018-10-01
End date
2019-04-30
Keywords
Health
Additional Keywords
Vaccine uptake, herd immunity, information
JEL code(s)
Secondary IDs
Abstract
We run a large-scale RCT to understand the behavioural processes that guide decisions to vaccinate. The experiment varies the text of postal letters send to individuals eligible for free influenza vaccines. The experiment is run in collaboration with the municipal health authorities in six different municipalities with historically high and low influenza vaccine coverage.
External Link(s)

Registration Citation

Citation
Sääksvuori, Lauri. 2018. "Information and vaccine uptake." AEA RCT Registry. November 19. https://doi.org/10.1257/rct.3520-1.1
Former Citation
Sääksvuori, Lauri. 2018. "Information and vaccine uptake." AEA RCT Registry. November 19. https://www.socialscienceregistry.org/trials/3520/history/213412
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
Intervention Start Date
2018-10-31
Intervention End Date
2018-11-01

Primary Outcomes

Primary Outcomes (end points)
Vaccine uptake (as recorded in the administrative Register of Primary Health Care visits)

Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
We run the analysis by gender and municipality. We investigate the effect of our intervention separate in regions with low and high historical vaccine coverage.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Random assignment at household level. In two active treatment arms, individuals receive postal letters that contain information about the benefits of influence vaccines.
Experimental Design Details
Random assignment at household level. In two active treatment arms, individuals receive postal letters that contain information about the benefits of influence vaccines.
Randomization Method
Randomization at office using computer code (Stata)
Randomization Unit
Households (including single households and couples)
Was the treatment clustered?
Yes

Experiment Characteristics

Sample size: planned number of clusters
Control treatment: 1739 clusters
T1: 16436 clusters
T2: 16436 clusters
Sample size: planned number of observations
Control treatment: 2466 individuals T1: 22839 individuals T1: 22839 individuals
Sample size (or number of clusters) by treatment arms
See above.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Not straightforward to compute as cluster size varies (household size is either 1 or 2). A very conservative estimate assuming interclass correlation 1 and sd. 0.5 gives a minimal detectable effect size 1.55ppt for treatment comparison T1 vs. T2, and 3.53ppt for T0 v. T1(or T2).
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Institutional review board (IRB) of National Institute for Health and Welfare / Institutional review board (IRB) 00007085
IRB Approval Date
2018-08-21
IRB Approval Number
N/A
Analysis Plan

Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
Yes
Intervention Completion Date
March 17, 2019, 12:00 +00:00
Data Collection Complete
Yes
Data Collection Completion Date
March 17, 2019, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
34692
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
47683
Final Sample Size (or Number of Clusters) by Treatment Arms
2450, 2445 and 2429 individuals per treatment arm in the Western region. 19996 and 20362 individuals per treatment arm in the Southern region
Data Publication

Data Publication

Is public data available?
No

There is information in this trial unavailable to the public. Use the button below to request access.

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Program Files

Program Files
Yes
Program Files URL
https://osf.io/qdrc4/ or https://doi.org/10.17605/OSF.IO/QDRC4
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials

Description
In this study, we found that sending reminders was an effective and scalable intervention strategy to increase vaccination coverage in an older adult population with low vaccination coverage. Communicating the social benefits of vaccinations, in addition to individual benefits, did not enhance vaccination coverage. The effectiveness of letter reminders about the benefits of vaccination to improve influenza vaccination coverage may depend on the prior vaccination history of the population.
Citation
Sääksvuori L, Betsch C, Nohynek H, Salo H, Sivelä J, Böhm R (2022) Information nudges for influenza vaccination: Evidence from a large-scale cluster-randomized controlled trial in Finland. PLoS Med 19(2): e1003919. https://doi.org/10.1371/journal.pmed.1003919
URL
https://doi.org/10.1371/journal.pmed.1003919