NCT05499299

Brief Summary

The success of vaccination programs often depends on the effectiveness of the vaccine messages, particularly during emergencies such as the COVID-19 pandemic. The current suboptimal uptake of COVID-19 vaccines across many parts of the world highlights the tremendous challenges in overcoming vaccine hesitancy and refusal even in the context of a world-devastating pandemic. The investigators conducted a randomized controlled trial in Hong Kong to evaluate the impact of seven vaccine messages on COVID-19 vaccine uptake (with the government slogan as the control). The participants included 127,000 individuals who googled COVID-19-related information during July-October 2021.

Trial Health

87
On Track

Trial Health Score

Automated assessment based on enrollment pace, timeline, and geographic reach

Enrollment
127,000

participants targeted

Target at P75+ for not_applicable

Timeline
Completed

Started Jul 2021

Shorter than P25 for not_applicable

Geographic Reach
1 country

1 active site

Status
completed

Health score is calculated from publicly available data and should be used for screening purposes only.

Trial Relationships

Click on a node to explore related trials.

Study Timeline

Key milestones and dates

Study Start

First participant enrolled

July 1, 2021

Completed
4 months until next milestone

Primary Completion

Last participant's last visit for primary outcome

October 31, 2021

Completed
5 months until next milestone

Study Completion

Last participant's last visit for all outcomes

April 1, 2022

Completed
4 months until next milestone

First Submitted

Initial submission to the registry

August 10, 2022

Completed
2 days until next milestone

First Posted

Study publicly available on registry

August 12, 2022

Completed
Last Updated

August 16, 2022

Status Verified

August 1, 2022

Enrollment Period

4 months

First QC Date

August 10, 2022

Last Update Submit

August 12, 2022

Conditions

Vaccine-Preventable DiseasesVaccine Refusal

Keywords

Vaccine hesitancyGoogle adsVaccine messagesVaccine confidence

Outcome Measures

Primary Outcomes (1)

  • Number of bookings following each message delivery within 6 hours

    The number of bookings made within X = 6 hours following each message delivery

    6 hours

Secondary Outcomes (2)

  • Number of bookings following each message delivery within 3 hours

    3 hours

  • Number of bookings following each message delivery within 12 hours

    12 hours

Study Arms (7)

Government

ACTIVE COMPARATOR

Participants were shown with the government slogan for the COVID-19 vaccine campaign in 2021. This was the control arm.

Behavioral: Google ads

Comparison

EXPERIMENTAL

The ad emphasized that vaccine uptake in Hong Kong substantially lagged behind that in comparable populations such as Singapore and the UK.

Behavioral: Google ads

Exemption

EXPERIMENTAL

The ad emphasized that vaccinated people could be exempted from some disruptive control measures such as mandatory testing

Behavioral: Google ads

Family

EXPERIMENTAL

The ad prompted people to get vaccinated in order to protect their family.

Behavioral: Google ads

Lottery

EXPERIMENTAL

The ad prompted people to get vaccinated in order to be eligible for the numerous COVID-19 lotteries in Hong Kong

Behavioral: Google ads

Mortality

EXPERIMENTAL

The ad emphasized that COVID-19 has caused millions of deaths worldwide.

Behavioral: Google ads

Reopen

EXPERIMENTAL

The ad prompted people to get vaccinated to help Hong Kong reopen sooner.

Behavioral: Google ads

Interventions

Google adsBEHAVIORAL

Individuals who googled COVID-19 information in Hong Kong were randomized to see one of the seven ads and, if they clicked on the ads, the corresponding vaccine message on our website

ComparisonExemptionFamilyGovernmentLotteryMortalityReopen

Eligibility Criteria

Sexall
Healthy VolunteersYes
Age GroupsChild (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

  • General users of Google search in Hong Kong

You may not qualify if:

  • None

Contact the study team to confirm eligibility.

Sponsors & Collaborators

Study Sites (1)

The University of Hong Kong

Hong Kong, Hong Kong

Location

MeSH Terms

Conditions

Vaccine-Preventable DiseasesVaccination RefusalVaccination Hesitancy

Condition Hierarchy (Ancestors)

InfectionsTreatment RefusalTreatment Adherence and ComplianceHealth BehaviorBehavior

Study Officials

  • Joseph T Wu, PhD

    The University of Hong Kong

    PRINCIPAL INVESTIGATOR

Study Design

Study Type
interventional
Phase
not applicable
Allocation
RANDOMIZED
Masking
SINGLE
Who Masked
PARTICIPANT
Purpose
HEALTH SERVICES RESEARCH
Intervention Model
PARALLEL
Sponsor Type
OTHER
Responsible Party
SPONSOR

Study Record Dates

First Submitted

August 10, 2022

First Posted

August 12, 2022

Study Start

July 1, 2021

Primary Completion

October 31, 2021

Study Completion

April 1, 2022

Last Updated

August 16, 2022

Record last verified: 2022-08

Data Sharing

IPD Sharing
Will share

Proposals should be directed to kathysleung@connect.hku.hk; to gain access, data requestors will need to sign a data access agreement

Shared Documents
STUDY PROTOCOL
Time Frame
Beginning 9 months and ending 36 months following article publication
Access Criteria
Researchers who provide a methodologically sound proposal for meta-analysis. Proposals should be directed to Kathyleung@connect.hku.hk; to gain access, data requestors will need to sign a data access agreement.

Locations

HK(1)