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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.
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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Government | Active Comparator | Participants were shown with the government slogan for the COVID-19 vaccine campaign in 2021. This was the control arm. |
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| Comparison | Experimental | The ad emphasized that vaccine uptake in Hong Kong substantially lagged behind that in comparable populations such as Singapore and the UK. |
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| Exemption | Experimental | The ad emphasized that vaccinated people could be exempted from some disruptive control measures such as mandatory testing |
|
| Family | Experimental | The ad prompted people to get vaccinated in order to protect their family. |
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| Lottery | Experimental | The ad prompted people to get vaccinated in order to be eligible for the numerous COVID-19 lotteries in Hong Kong |
|
| Mortality |
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Google ads | Behavioral | 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 |
| Measure | Description | Time Frame |
|---|---|---|
| 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 |
| Measure | Description | Time Frame |
|---|---|---|
| Number of bookings following each message delivery within 3 hours | The number of bookings made within X = 3 hours following each message delivery | 3 hours |
| Number of bookings following each message delivery within 12 hours |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Joseph T Wu, PhD | The University of Hong Kong | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| The University of Hong Kong | Hong Kong | Hong Kong |
Proposals should be directed to kathysleung@connect.hku.hk; to gain access, data requestors will need to sign a data access agreement
Beginning 9 months and ending 36 months following article publication
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.
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| ID | Term |
|---|---|
| D000079263 | Vaccine-Preventable Diseases |
| D000072758 | Vaccination Refusal |
| D000088823 | Vaccination Hesitancy |
| ID | Term |
|---|---|
| D007239 | Infections |
| D016312 | Treatment Refusal |
| D000074822 | Treatment Adherence and Compliance |
| D015438 | Health Behavior |
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The ad emphasized that COVID-19 has caused millions of deaths worldwide. |
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| Reopen | Experimental | The ad prompted people to get vaccinated to help Hong Kong reopen sooner. |
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The number of bookings made within X = 12 hours following each message delivery
| 12 hours |
| D001519 |
| Behavior |