Optimizing Weblinks Used in Digital Vaccination Invitations to Raise Trust and Booking Intention: Online Experiment 1
Phase: NA
Conditions: Vaccination
Sponsor: University of Essex

Document related to the study: “Optimizing Weblinks Used in Digital 
Vaccination Invitations to Raise Trust and Booking Intention: Online 
Experiment 1” 
 
The document was registered on AsPredicted on the 12/29/2021 
 
 
The document includes hypotheses, design, dependent variables and analytical plan for the 
study “Optimizing Weblinks Used in Digital Vaccination Invitations to Raise Trust and 
Booking Intention: Online Experiment 1” 

Version of AsPredicted Questions: 2.00
PDF generated: 2026/02/09 01:40 (PT)
Available at https://aspredicted.org/vrwy-5qkf.pdf
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Foster trustworthy digital communication about vaccines with better links (#84106)
Author(s)
This pre-registration is currently anonymous to enable blind peer-review.
It has one author.
Pre-registered on:
2021/12/29 07:23 (PT)
1) Have any data been collected for this study already?
No, no data have been collected for this study yet.
2) What's the main question being asked or hypothesis being tested in this study?
Participants will read one of two emails of invitation to get a booster vaccine.
One email will include the accurx web link that was used by the NHS (e.g., in text invites) and the other one will include an improved version of it:
https://vaccinevaccine-booking.nhs.uk
The UK and US samples will be shown slightly diﬀerent emails (sent by the NHS in the UK and from Pharma-US in the US).
Hypotheses
1. The email that includes the accurx web link will be perceived as less trustworthy, than the email including the improved web address.
2. Participants will be more likely to agree to book a vaccine appointment based on the email that includes the improved link than based on the
email that includes the accurx web link.
3. Participants will ﬁnd the improved link more ﬂuent than the accurx web link.
4. Participants will be more likely to correctly identify the organisation that sent them the link based on the improved link than based on the accurx
web link.
3) Describe the key dependent variable(s) specifying how they will be measured.
Participants will rate each text message in terms of how trustworthy it seems on a 5 point Likert scale (1: Very suspicious to 5: very trustworthy),
how ﬂuent is the link on a 5 point Likert scale (1: very diﬃcult – 5: very easy) and how likely they would be to book an appointment on a 5 point
Likert scale (1: very unlikely to 5: very likely). To identify the host organisation of the website, participants will select one answer from a list of four
possible answers (the NHS, pharma-us, accurx or unclear/I don't know).
4) How many and which conditions will participants be assigned to?
Participants will be randomly allocated to either the email that includes the accurx link or to the improved one. Participants will see the UK or US
version as a function of their country of residence.
5) Specify exactly which analyses you will conduct to examine the main question/hypothesis.
We will test hypotheses 1-3 with a within-subject analysis of variance with the web link manipulation (2 conditions) and the country (US vs. UK) as
between subject factors and the diﬀerent variable about the email perception as dependent variables.
We will also test the robustness of the eﬀect by including participants' sociodemographic characteristics (e.g., gender, age, education).
6) Describe exactly how outliers will be deﬁned and handled, and your precise rule(s) for excluding observations.
We will ﬁlter participants out if we judge they completed the study too fast or failed the attention check.
7) How many observations will be collected or what will determine sample size? No need to justify decision, but be precise about
exactly how the number will be determined.
We will invite 1200 participants to complete an online study (600 from the US and 600 from the UK).
8) Anything else you would like to pre-register? (e.g., secondary analyses, variables collected for exploratory purposes, unusual
analyses planned?)
The study is part of a wider web survey that includes questions about the trustworthiness of text messages and vaccination rates.