VaccinationNCT07516600
Optimizing Weblinks Used in Digital Vaccination Invitations to Raise Trust and Booking Intention: Online Experiment 1
A study testing Improved trust and engagement in people with Vaccination, run by University of Essex at 1 site in United Kingdom.
Trial summary
This study investigates whether the design of weblinks in digital vaccination invitations affects how much people trust the message and their willingness to book an appointment. Researchers compare a standard third-party weblink used by the NHS ("accurx.thirdparty.nhs.uk/r/aafwaczmd5") with an improved, more… Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Vaccination
- What is being tested?
- Improved trust and engagement
- Type of treatment
- Vaccines, Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 1,226 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 3 Jan 2022to 10 Jan 2022
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Residency: Must be a resident of either the United Kingdom or the United States
Who cannot join
- Attention Failure: Participants who failed the designated attention check included within the survey will be excluded from the analysis
- Speeding: Participants who completed the study "too fast"-indicating a lack of meaningful engagement with the experimental stimuli-were filtered out
Trial locations and contacts
1 site in 1 country.
About this study
This study investigates whether the design of weblinks in digital vaccination invitations affects how much people trust the message and their willingness to book an appointment. Researchers compare a standard third-party weblink used by the NHS ("accurx.thirdparty.nhs.uk/r/aafwaczmd5") with an improved, more transparent weblink (https://vaccine-booking.nhs.uk).
The study tests the hypothesis that the improved link will be perceived as more trustworthy and easier to read than the standard link. Further, the study tests whether participants would be more likely to correctly identify the sender and would be more willing to book a vaccine when shown the improved link.
To test these effects, the investigators planned to conduct a study with 600 participants from the United Kingdom and 600 from the United States. Participants will be randomly assigned to view one of the two hypothetical email versions. UK participants will see an email that appears to be from the NHS. US participants will see an email from a fictitious pharmacy (Pharma-US).This research aims to provide evidence on how to design more trustworthy digital health communications when recipients are asked to click a weblink.
Read the detailed description
This randomised experimental study investigates how weblink design influences the perceived trustworthiness of digital health communications. As digital invitations (e.g., emails and SMS) have become standard for public health initiatives such as vaccination programmes, the use of third-party or disfluent (hard-to-read) web links may inadvertently undermine trust.
Study Protocol and Intervention Participants will be randomly allocated to one of two experimental conditions. In both conditions, participants will view a hypothetical email invitation for a COVID-19 booster vaccine. The content of the emails will remain identical except for the format of the embedded booking link: Control Condition: Features the "accurx" web link (accurx.thirdparty.nhs.uk/r/aafwaczmd5), a third-party format previously used in COVID-19 vaccination invitations by the National Health Service (NHS) in the UK. Experimental Condition: Features an improved, transparent - "clear" - weblink that was designed to be easier to read and clearly identifies the host organisation (e.g., https://vaccine-booking.nhs.uk). The UK and US respondents will see different hypothetical emails tailored to their country of residence: UK participants will see invitations sent from the NHS, while US participants will see invitations from a fictitious pharmacy (Pharma-US). Unlike the UK, COVID-19 vaccination in the US was predominantly organised by local pharmacies.
Primary Hypotheses
The study is designed to test four primary hypotheses:
- Emails containing the control "accurx" link will be rated as significantly less trustworthy than those with the improved weblink.
- The improved link will increase the intention to book a vaccination appointment.
- Participants will perceive the improved link as being more fluent (easier to read) than the control link.
- The improved link will facilitate significantly higher accuracy in identifying the host organisation that sent the communication.
Measurement Following the presentation of the stimulus, participants will rate the emails on three 5-point Likert scales: trustworthiness (1: Very suspicious to 5: Very trustworthy), link fluency (1: Very difficult to 5: Very easy), and booking intention (1: Very unlikely to 5: Very likely). Host identification is assessed via a multiple-choice question with four options: the NHS, Pharma-US, Accurx, or "Not sure". The investigators aim to collect data from 600 participants from the UK and 600 from the US. Participants will be invited to complete the study via an online platform.
Data will be analysed using a within-subject analysis of variance (ANOVA) to examine the effects of link manipulation, with further robustness checks incorporating sociodemographic variables such as age, gender, and education. UK and US participants data will be analysed separately if needed. This study is conducted as part of a larger research project exploring the broader relationship between the trustworthiness of digital messages and national vaccination rates.
The study hypotheses, design, measures and analyses were preregistered before the start of data collection on a different platform (AsPredicted). This time stamped preregistration protocol is link as a document in this registration.
- Conditions
- Vaccination
- Being tested
- Improved trust and engagement
- Keywords
- health communication, digital health, trust
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Improved trust and engagementBehavioural
The intervention involves presenting a digital COVID-19 booster vaccination invitation via email. Participants are randomly allocated to view one of two versions of the invitation to evaluate the impact of the weblink design on trust and behaviour. To ensure local relevance, the email content is adapted based on the participant's country of residence; participants in the United Kingdom see invitations sent from the NHS, while those in the United States see invitations from Pharma-US
| Study group | Role | What they receive |
|---|---|---|
| Control | No intervention | Participants were assigned to view a vaccination invitation email containing the control weblink (UK participants: accurx.thirdparty.nhs.uk/r/aafwaczmd5; US participants: accurx.thirdparty.pharma-us.com/r/aafwaczmd5 |
| Clear Link | Experimental | Participants were assigned to view an email containing an improved version of the link (UK participants: https://vaccine-booking.nhs.uk; US participants: https://vaccine-booking.pharma-us.com) Receives: Behavioral: Improved trust and engagement |
What is being measured
The primary outcome is the main question the study is designed to answer.
Perceived Trustworthiness
Participants rated the perceived trustworthiness of the vaccination invitation email on a 5-point Likert scale, where 1 represents "Very suspicious" and 5 represents "Very trustworthy"
Measured: Immediately after intervention
Booking Intention
Participants rated their likelihood of booking a vaccine appointment based on the email invitation using a 5-point Likert scale ranging from 1 ("Very unlikely") to 5 ("Very likely")
Measured: Immediately after intervention
Secondary outcomes (2)
Ease of reading
Participants assessed the reading ease or fluency of the embedded weblink on a 5-point Likert scale, where 1 is "Very difficult" and 5 is "Very easy"
Measured: Immediately after intervention
Host Identification
Participants were asked to identify the organisation that sent the communication by selecting one answer from a multiple-choice list of four options: the NHS, Pharma-US, Accurx, or Unclear/I don't know
Measured: Immediately after intervention
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted8 Apr 2026
- Study start3 Jan 2022
- Primary completion10 Jan 2022
- Study completion10 Jan 2022
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for VaccinationStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- This study followed a Parallel Assignment interventional model. Participants were randomly allocated to one of two independent groups to evaluate the impact of the weblink design on trust and engagement with digital health communication.
- Masking
- Triple blind
- Who is masked
- Participant, Investigator, Outcomes assessor
- Enrolment
- 1,226 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Essex
- Sponsor type
- University, hospital or other
- Collaborators
- University of Southern California, Department of Health and Social Care, UK, Kingston University
- Responsible party
- Principal investigator, Marie Juanchich, University of Essex
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07516600
- Sponsor's protocol ID
- ETH 2122-0265 Expe1
- Other IDs
- CRUSA210009
- Status last verified
- Mar 2026
- First submitted
- 24 Mar 2026
- Last updated
- 8 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: Anonymised study data is shared on the Open Science Framework.
Study at a glance
From the registry record, last updated by the sponsor on 8 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Optimizing Weblinks Used in Digital Vaccination Invitations to Raise Trust and Booking Intention: Online Experiment 1
- ClinicalTrials.gov ID
- NCT07516600
- Acronym / sponsor ID
- ETH 2122-0265 Expe1
- Conditions
- Vaccination
- Keywords
- health communication, digital health, trust
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 1,226 participants (actual)
- Lead sponsor
- University of EssexUniversity, hospital or other
- Collaborators
- University of Southern California, Department of Health and Social Care, UK, Kingston University
- Study start
- 3 Jan 2022 (actual)
- Primary completion
- 10 Jan 2022 (actual)
- Study completion
- 10 Jan 2022 (actual)
- First posted
- 8 Apr 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study investigates whether the design of weblinks in digital vaccination invitations affects how much people trust the message and their willingness to book an appointment. Researchers compare a standard third-party weblink used by the NHS ("accurx.thirdparty.nhs.uk/r/aafwaczmd5") with an improved, more transparent weblink (https://vaccine-booking.nhs.uk).
The study tests the hypothesis that the improved link will be perceived as more trustworthy and easier to read than the standard link. Further, the study tests whether participants would be more likely to correctly identify the sender and would be more willing to book a vaccine when shown the improved link.
To test these effects, the investigators planned to conduct a study with 600 participants from the United Kingdom and 600 from the United States. Participants will be randomly assigned to view one of the two hypothetical email versions. UK participants will see an email that appears to be from the NHS. US participants will see an email from a fictitious pharmacy (Pharma-US).This research aims to provide evidence on how to design more trustworthy digital health communications when recipients are asked to click a weblink.
Detailed description
This randomised experimental study investigates how weblink design influences the perceived trustworthiness of digital health communications. As digital invitations (e.g., emails and SMS) have become standard for public health initiatives such as vaccination programmes, the use of third-party or disfluent (hard-to-read) web links may inadvertently undermine trust.
Study Protocol and Intervention Participants will be randomly allocated to one of two experimental conditions. In both conditions, participants will view a hypothetical email invitation for a COVID-19 booster vaccine. The content of the emails will remain identical except for the format of the embedded booking link: Control Condition: Features the "accurx" web link (accurx.thirdparty.nhs.uk/r/aafwaczmd5), a third-party format previously used in COVID-19 vaccination invitations by the National Health Service (NHS) in the UK. Experimental Condition: Features an improved, transparent - "clear" - weblink that was designed to be easier to read and clearly identifies the host organisation (e.g., https://vaccine-booking.nhs.uk). The UK and US respondents will see different hypothetical emails tailored to their country of residence: UK participants will see invitations sent from the NHS, while US participants will see invitations from a fictitious pharmacy (Pharma-US). Unlike the UK, COVID-19 vaccination in the US was predominantly organised by local pharmacies.
Primary Hypotheses
The study is designed to test four primary hypotheses:
- Emails containing the control "accurx" link will be rated as significantly less trustworthy than those with the improved weblink.
- The improved link will increase the intention to book a vaccination appointment.
- Participants will perceive the improved link as being more fluent (easier to read) than the control link.
- The improved link will facilitate significantly higher accuracy in identifying the host organisation that sent the communication.
Measurement Following the presentation of the stimulus, participants will rate the emails on three 5-point Likert scales: trustworthiness (1: Very suspicious to 5: Very trustworthy), link fluency (1: Very difficult to 5: Very easy), and booking intention (1: Very unlikely to 5: Very likely). Host identification is assessed via a multiple-choice question with four options: the NHS, Pharma-US, Accurx, or "Not sure". The investigators aim to collect data from 600 participants from the UK and 600 from the US. Participants will be invited to complete the study via an online platform.
Data will be analysed using a within-subject analysis of variance (ANOVA) to examine the effects of link manipulation, with further robustness checks incorporating sociodemographic variables such as age, gender, and education. UK and US participants data will be analysed separately if needed. This study is conducted as part of a larger research project exploring the broader relationship between the trustworthiness of digital messages and national vaccination rates.
The study hypotheses, design, measures and analyses were preregistered before the start of data collection on a different platform (AsPredicted). This time stamped preregistration protocol is link as a document in this registration.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (participant, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- This study followed a Parallel Assignment interventional model. Participants were randomly allocated to one of two independent groups to evaluate the impact of the weblink design on trust and engagement with digital health communication.
| Arm | Type | Receives |
|---|---|---|
| Control | No intervention | –Participants were assigned to view a vaccination invitation email containing the control weblink (UK participants: accurx.thirdparty.nhs.uk/r/aafwaczmd5; US participants: accurx.thirdparty.pharma-us.com/r/aafwaczmd5 |
| Clear Link | Experimental | Behavioral: Improved trust and engagementParticipants were assigned to view an email containing an improved version of the link (UK participants: https://vaccine-booking.nhs.uk; US participants: https://vaccine-booking.pharma-us.com) |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Residency: Must be a resident of either the United Kingdom or the United States
Key exclusion criteria (2 listed)
- Attention Failure: Participants who failed the designated attention check included within the survey will be excluded from the analysis
- Speeding: Participants who completed the study "too fast"-indicating a lack of meaningful engagement with the experimental stimuli-were filtered out
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Improved trust and engagementThe intervention involves presenting a digital COVID-19 booster vaccination invitation via email. Participants are randomly allocated to view one of two versions of the invitation to evaluate the impact of the weblink design on trust and behaviour. To ensure local relevance, the email content is adapted based on the participant's country of residence; participants in the United Kingdom see invitations sent from the NHS, while those in the United States see invitations from Pharma-US | Behavioural | Clear Link |
Primary outcome
Perceived Trustworthiness
Time frame: Immediately after intervention
Participants rated the perceived trustworthiness of the vaccination invitation email on a 5-point Likert scale, where 1 represents "Very suspicious" and 5 represents "Very trustworthy"
Booking Intention
Time frame: Immediately after intervention
Participants rated their likelihood of booking a vaccine appointment based on the email invitation using a 5-point Likert scale ranging from 1 ("Very unlikely") to 5 ("Very likely")
2 secondary outcomes
Ease of reading
Time frame: Immediately after intervention
Host Identification
Time frame: Immediately after intervention
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 8 Apr 2026.
- Open Science Framework: Project Repository containing data, protocols, and materials.Link provided by the sponsor.
- Individual participant dataSharing planned: Yes. Anonymised study data is shared on the Open Science Framework.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Improved trust and engagement in people with Vaccination, run by University of Essex at 1 site in United Kingdom.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 8 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Perceived Trustworthiness (time frame: Immediately after intervention). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 Apr 2026; AzTrials last refreshed its copy on 2 Nov 2026.