Education, Immigration and HPV Vaccination: an Informational Randomized Trial

Last registered on December 21, 2024
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Pre-Trial

Trial Information

General Information

Title
Education, Immigration and HPV Vaccination: an Informational Randomized Trial
RCT ID
AEARCTR-0007668
Initial registration date
August 17, 2021

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 19, 2021, 11:06 AM EDT

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

Last updated
December 21, 2024, 5:42 PM EST

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

Locations

Country
Sweden
Region
Stockholm County

Primary Investigator

Name
Lisen Arnheim Dahlström
Affiliation
Karolinska Institutet
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Other Primary Investigator(s)

PI Name
Alice Dominici
PI Affiliation
European University Institute
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Additional Trial Information

Status
Completed
Start date
2021-06-14
End date
2022-10-31
Keywords
Behavior, Health
Additional Keywords
Information framing, vaccines
JEL code(s)
Secondary IDs
NCT04905030
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
Counteracting misinformation on childhood vaccines remains a priority for
public health in industrialized countries. Previous research showed that
misinformation-induced vaccine hesitancy particularly concerns very highly
or very lowly educated parents, and, especially in Europe, specific groups of
immigrants. Misinformation framing directly targets specific sub-population
of parents by exploiting different cognitive biases, and specific concerns
based on cultural norms: we aim at testing the effectiveness of similar framing
techniques applied to positive information on the HPV vaccine by conducting a stratified
Randomized Controlled Trial in Stockholm, Sweden. We randomize emotionally
and scientifically/statistically framed information addressing the specific
concerns reported by the epidemiological literature, and test whether they improve HPV vaccination uptake and reduce common vaccines misconceptions.
External Link(s)

Registration Citation

Citation
Arnheim Dahlström, Lisen and Alice Dominici. 2024. "Education, Immigration and HPV Vaccination: an Informational Randomized Trial." AEA RCT Registry. December 21. https://doi.org/10.1257/rct.7668-2.1
Sponsors & Partners

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Experimental Details

Interventions

Intervention(s)
Intervention (Hidden)
We randomize an informational intervention at the individual level. It consists of a leaflet (approximately 650 words long) containing: a reminder of the upcoming vaccination; information on HPV (Human Papilloma Virus), and the type of cancers it can induce in both women and men; - the consequences that HPV-induced cancers can have in terms of fertility loss, mortality and the need of invasive medical treatment. The rationale is to highlight that the vaccine protects against these risks, rather than causing them (e.g. among Muslim immigrants a common misconception is that vaccines cause sterility, more generally misinformation often cites cancer and other serious illnesses as side effects of vaccines). While the length of the information leaflet is constant across treatment arms, the framing changes:
- T1, Emotional framing: we use common terminology, and the risks associated to HPV-induced cancers are described by the emotionally-charged testimonies of Swedish cancer survivors.
- T2, Statistical and scientific framing: we use scientific terminology, and the risks associated to HPV-induced cancers are described in terms of incidence and mortality rates in Sweden.
- C, Pure placebo: besides the reminder of the upcoming vaccination, there is no substantive information on the vaccine, but rather a recount of the vaccination program's history.

The information leaflet is available in Swedish, English, Arabic and Persian.
Intervention Start Date
2021-06-14
Intervention End Date
2021-08-31

Primary Outcomes

Primary Outcomes (end points)
1. Actual decision to vaccinate child against HPV
Investigators will assess if there are significant differences in the frequency of parents who decide to vaccinate across
treatment arms, within each stratum
[This outcome is extracted from national vaccination registers in November 2021]
2. Self-reported beliefs about false risks of the HPV vaccine, and trust in health authorities
The investigators will examine whether across treatment groups, within strata, parents show different degrees of
agreement with false statements concerning the risks of HPV
[Time Frame: outcome will be assessed in the initial survey administered right after the informational intervention (June-August 2021) and
in the endline survey (November 2021)]
Primary Outcomes (explanation)
Beliefs about false risks of vaccines: we assess the agreement with the following statements on a 5-points Likert scale:
-Vaccines weaken and overload the immune system
-Vaccines can cause the disease against which they protect
-Vaccines can produce serious side effects
We will use individual measures and their arithmetic mean.
We also assess self-reported trust in health authorities by asking agreement with the following statement:
- I trust the opinion of health professionals and health authorities about vaccines

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Randomization at the individual level within strata, defined by immigration status and education level.
Experimental Design Details
Randomization Method
By computer, performed by the implementation partner (Statistics Sweden, i.e. the national Swedish statistics bureau)
Randomization Unit
Individual (i.e. mother)
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
7500 invited, 2500 expected participants. Details in attachment
Sample size: planned number of observations
7500 invited, 2500 expected participants. Details in attachment
Sample size (or number of clusters) by treatment arms
Within each stratum, we expect 500 actual participants, divided as follows: 120 pure placebo (C), 190 emotional framing (T1), 190 statistical/scientific framing (T2). i.e. of the initial 7500 invited subjects, 38% are randomized to T1, 38% to T2 and the remaining 24% to C.
Details in attachment
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Details in attachment
Supporting Documents and Materials

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IRB

Institutional Review Boards (IRBs)

IRB Name
Swedish Ethical Review Authority
IRB Approval Date
2021-04-21
IRB Approval Number
2021-01225
Analysis Plan

Analysis Plan Documents

Pre-Analysis Plan "Targeting vaccine information framing to recipients' education: a randomized trial"

MD5: b11ffa27ef26aa16b8b25fa4acf0d19c

SHA1: b58599b5c8670907129c0b7b178f3a761e1b31aa

Uploaded At: August 17, 2021

Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
Yes
Intervention Completion Date
December 01, 2021, 12:00 +00:00
Data Collection Complete
Yes
Data Collection Completion Date
March 01, 2022, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
7616 (randomization at individual level)
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
7616 mothers
Final Sample Size (or Number of Clusters) by Treatment Arms
1826 control, 2884 T1 (emotional framing), 2905 T2 (scientific framing)
Data Publication

Data Publication

Is public data available?
No

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Program Files

Program Files
No
Reports, Papers & Other Materials

Relevant Paper(s)

Abstract
We investigate tailoring information framing to recipients’ backgrounds to boost vaccination uptakes. 7616 Swedish mothers stratified by education and immigration background received a leaflet on their children’s upcoming HPV vaccination opportunity. The leaflet’s framing was randomized between emotional and scientific, with control units receiving an uninformative announcement. Mothers with compulsory schooling exposed to scientific framing increased their uptake by 5.7 percentage points (7.25%). The effect was driven by attentive readers with little previous HPV knowledge. Emotional framing decreased uptake by 4.8 percentage points (5.41%) among high school-educated mothers who read superficially and were more hesitant at baseline.
Citation
DOMINICI, Alice, DAHLSTRÖM, Lisen Arnheim, Targeting vaccine information framing to recipients’ education : a randomized trial, EUI, ECO, Working Paper, 2023/02 - https://hdl.handle.net/1814/76012
URL
https://cadmus.eui.eu/handle/1814/76012

Reports & Other Materials