Volatility and Heterogeneity of Vaccine Sentiments Means Continuous Monitoring is Needed When Measuring Message Effectiveness

Not Applicable

Completed

• Conditions: Vaccine-Preventable Diseases; Vaccine Refusal
• Interventions: Behavioral: Google ads

• Registration Number: NCT05499299
• Lead Sponsor: The University of Hong Kong

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.

Detailed Description

This study aims to evaluate the effectiveness of using the Google advertising platforms on influencing the uptake of COVID-19 vaccines in Hong Kong. When completed, the rich database compiled through this proposed study will provide increased insight into vaccine hesitancy in Hong Kong. Insights from the optimised online advertising trial can aid in providing crucial technical and theoretical support to the relevant health authorities for any potential evidence-based policy intervention in addressing vaccine hesitancy issues or the public's concerns towards vaccines in Hong Kong.

Study Timeline

• Study Start: 2021-07-01
• Primary Completion: 2021-10-31
• Study Completion: 2022-04-01
• Status Verified: 2022-08
• Study First Submitted: 2022-08-10
• Study First Submitted QC: 2022-08-10
• Study First Posted: 2022-08-12
• Last Update Submitted: 2022-08-12
• Last Update Posted: 2022-08-16

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 127000

Inclusion Criteria

• General users of Google search in Hong Kong

Exclusion Criteria

• None

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Mortality	Google ads	The ad emphasized that COVID-19 has caused millions of deaths worldwide.
Reopen	Google ads	The ad prompted people to get vaccinated to help Hong Kong reopen sooner.
Comparison	Google ads	The ad emphasized that vaccine uptake in Hong Kong substantially lagged behind that in comparable populations such as Singapore and the UK.
Exemption	Google ads	The ad emphasized that vaccinated people could be exempted from some disruptive control measures such as mandatory testing
Lottery	Google ads	The ad prompted people to get vaccinated in order to be eligible for the numerous COVID-19 lotteries in Hong Kong
Government	Google ads	Participants were shown with the government slogan for the COVID-19 vaccine campaign in 2021. This was the control arm.
Family	Google ads	The ad prompted people to get vaccinated in order to protect their family.

Primary Outcome Measures

Name	Time	Method
Number of bookings following each message delivery within 6 hours	6 hours	The number of bookings made within X = 6 hours following each message delivery

Secondary Outcome Measures

Name	Time	Method
Number of bookings following each message delivery within 3 hours	3 hours	The number of bookings made within X = 3 hours following each message delivery
Number of bookings following each message delivery within 12 hours	12 hours	The number of bookings made within X = 12 hours following each message delivery

Trial Locations

Locations (1)

The University of Hong Kong; 🇭🇰 Hong Kong, Hong Kong