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Trial registered on ANZCTR


Registration number
ACTRN12622001404718
Ethics application status
Approved
Date submitted
25/10/2022
Date registered
2/11/2022
Date last updated
2/11/2022
Date data sharing statement initially provided
2/11/2022
Date results provided
2/11/2022
Type of registration
Retrospectively registered

Titles & IDs
Public title
Testing persuasive messages about booster doses of COVID-19 vaccines on intention to vaccinate in Australian adults
Scientific title
Testing persuasive messages about booster doses of COVID-19 vaccines on intention to vaccinate in Australian adults
Secondary ID [1] 308264 0
None
Universal Trial Number (UTN)
U1111-1284-3102
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Vaccination 328047 0
COVID-19 328109 0
Condition category
Condition code
Infection 325104 325104 0 0
Other infectious diseases
Public Health 325164 325164 0 0
Other public health

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
The intervention is a short piece of written material designed to encourage uptake of booster doses of COVID-19 vaccines. The messages were designed specifically for this study. The intervention is delivered as part of an online experiment over the internet. After answering some questions about themselves, participants are asked to read the written information on their computer or phone screen. They are given the intervention once. The anticipated time needed to read the text is approximately 30 seconds. Participants must spend a minimum of 30 seconds on this screen. This requirement to stay on the intervention screen is used for the purpose of encouraging adherence to the intervention.
Arm 1 is a message focusing on personal health impacts of vaccinating
Arm 2 is a message focusing on family and community health impacts of vaccinating
Arm 3 is a message focusing on non-health benefits of vaccinating, such as freedom from public health restrictions and ability to travel
Arm 4 is a message focusing on personal choice and control
Arm 5 is a control message, providing information on COVID-19 vaccine booster dose eligibility.
Intervention code [1] 324725 0
Behaviour
Comparator / control treatment
The control message provides information about COVID-19 vaccine booster dose eligibility. The control message is Arm 5.
Control group
Active

Outcomes
Primary outcome [1] 332927 0
Intention to receive a booster dose of COVID-19 vaccine. This outcome will be assessed using a single survey item, administered to participants immediately after the intervention.
Timepoint [1] 332927 0
Immediately after receiving the intervention
Secondary outcome [1] 415175 0
Belief about COVID-19 vaccine booster dose safety. This outcome will be assessed using a single survey item, administered to participants immediately after the intervention.
Timepoint [1] 415175 0
Immediately after the intervention.
Secondary outcome [2] 415180 0
Belief about COVID-19 vaccine booster dose effectiveness. This outcome will be assessed using a single survey item, administered to participants immediately after the intervention.
Timepoint [2] 415180 0
Immediately after the intervention
Secondary outcome [3] 415181 0
Belief about COVID-19 vaccine booster dose necessity to protect own health. This outcome will be assessed using a single survey item, administered to participants immediately after the intervention.
Timepoint [3] 415181 0
Immediately after the intervention
Secondary outcome [4] 415182 0
Belief about COVID-19 vaccine booster dose necessity to protect others' health. This outcome will be assessed using a single survey item, administered to participants immediately after the intervention.
Timepoint [4] 415182 0
Immediately after the intervention
Secondary outcome [5] 415183 0
Belief about the risk of contracting COVID-19 without a COVID-19 vaccine booster dose. This outcome will be assessed using a single survey item, administered to participants immediately after the intervention.
Timepoint [5] 415183 0
Immediately after the intervention

Eligibility
Key inclusion criteria
• 18 years or older
• living in Australia
• have had at least one dose of a COVID-19 vaccine
• competent in reading and writing in English
Minimum age
18 Years
Maximum age
No limit
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
• have not had a dose of COVID-19 vaccine, including Individuals who are medically exempt

Study design
Purpose of the study
Educational / counselling / training
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
central randomisation by computer
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
computerised sequence generation
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s


Intervention assignment
Parallel
Other design features
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis
Sample size: The aim is to recruit 480 vaccinated adults eligible for a booster dose of COVID-19 vaccine to ensure a sample size of 430 participants in each group. This allows for a drop-out/poor quality response rate of approximately 10%. The experiment will assign participants to 1 of 4 intervention groups or a control (5 groups in total). Assuming 80% power and significance at 0.01, a study involving 430 participants (86 per intervention group) would be powered to detect a small difference in outcomes measures between groups (effect size d=0.2). The sample size calculations were performed using G*Power, a program for power analysis and sample size calculations, using an ‘a Priori’ power analysis to calculate the sample size (n=430) required for the primary analysis, between group comparisons (the difference between two independent means). The calculations specified 80% power, significance at 0.01, and effect size of d=0.2. The significance (alpha) level was determined at 0.01 to account for 4 planned contrasts. Cohen’s d was interpreted using the following conventions: 0.2 represents a 'small' effect size, 0.5 represents a 'medium' effect size, 0.8 represents a 'large' effect size.

Analysis approach: The primary analysis will use an ANOVA to compare primary outcome measure (Intention) between the 4 intervention groups and the control (4 comparisons in total). The secondary analyses will use an ANOVA to compare the 5 secondary outcome measures (Beliefs) between groups and the control (4 comparisons in total for each belief). The sub-analysis of hesitant participants (identified by a stratifying question) will use an ANOVA to compare outcome measures (Intention and Beliefs) between groups and the control (4 comparisons per outcome measure).

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
17/12/2021
Date of last participant enrolment
Anticipated
Actual
24/12/2021
Date of last data collection
Anticipated
Actual
24/12/2021
Sample size
Target
480
Accrual to date
Final
487
Recruitment in Australia
Recruitment state(s)
ACT,NSW,NT,QLD,SA,TAS,WA,VIC

Funding & Sponsors
Funding source category [1] 312516 0
Government body
Name [1] 312516 0
NSW Health
Country [1] 312516 0
Australia
Primary sponsor type
Other Collaborative groups
Name
Kids Research
Address
178 Hawkesbury Rd, Westmead NSW 2145
Country
Australia
Secondary sponsor category [1] 314118 0
None
Name [1] 314118 0
None
Address [1] 314118 0
None
Country [1] 314118 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 311850 0
Sydney Children's Hospitals Network Human Research Ethics Committee
Ethics committee address [1] 311850 0
Ethics committee country [1] 311850 0
Australia
Date submitted for ethics approval [1] 311850 0
02/11/2021
Approval date [1] 311850 0
14/12/2021
Ethics approval number [1] 311850 0
2021/ETH00181 (Amendment ID 74493)

Summary
Brief summary
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 122594 0
Dr Maryke Steffens
Address 122594 0
National Centre for Immunisation Research and Surveillance (NCIRS), Kids Research, Corner Hawkesbury Road and, Hainsworth St, Westmead NSW 2145 Australia
Country 122594 0
Australia
Phone 122594 0
+61 2 98451433
Fax 122594 0
Email 122594 0
maryke.steffens@health.nsw.gov.au
Contact person for public queries
Name 122595 0
Maryke Steffens
Address 122595 0
NCIRS, Kids Research, Corner Hawkesbury Road and, Hainsworth St, Westmead NSW 2145 Australia
Country 122595 0
Australia
Phone 122595 0
+61 2 98451433
Fax 122595 0
Email 122595 0
maryke.steffens@health.nsw.gov.au
Contact person for scientific queries
Name 122596 0
Maryke Steffens
Address 122596 0
NCIRS, Kids Research, Corner Hawkesbury Road and, Hainsworth St, Westmead NSW 2145 Australia
Country 122596 0
Australia
Phone 122596 0
+61 2 98451433
Fax 122596 0
Email 122596 0
maryke.steffens@health.nsw.gov.au

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
Yes
What data in particular will be shared?
Individual de-identified participant data collected during the trial
When will data be available (start and end dates)?
Immediately following publication, no end date
Available to whom?
To researchers who provide a methodologically sound proposal
Available for what types of analyses?
for meta-analyses
How or where can data be obtained?
Access subject to approval by the Principal Investigator (maryke.steffens@health.nsw.gov.au)


What supporting documents are/will be available?

No Supporting Document Provided



Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
SourceTitleYear of PublicationDOI
EmbaseTesting persuasive messages about booster doses of COVID-19 vaccines on intention to vaccinate in Australian adults: A randomised controlled trial.2023https://dx.doi.org/10.1371/journal.pone.0286799
N.B. These documents automatically identified may not have been verified by the study sponsor.