Persuasive Messages for COVID-19 Vaccine Uptake: a Randomized Controlled Trial

Last registered on July 06, 2021

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Pre-Trial

Trial Information

General Information

Title

Persuasive Messages for COVID-19 Vaccine Uptake: a Randomized Controlled Trial

RCT ID

AEARCTR-0007864

Initial registration date

July 06, 2021

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published

July 06, 2021, 10:37 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Locations

Country

Ghana

Region

Primary Investigator

Name

Kathrin Durizzo

Affiliation

ETH Zurich

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Other Primary Investigator(s)

PI Name

Isabel Günther

PI Affiliation

ETH Zurich

Contact Investigator

PI Name

Edward Asiedu

PI Affiliation

University of Ghana Business School

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Additional Trial Information

Status

In development

Start date

2021-07-12

End date

2021-12-31

Keywords

Behavior, Health, Welfare

Additional Keywords

JEL code(s)

C93, H41, I12, I30

Secondary IDs

Abstract

The number of COVID-19 infections and deaths are still rising despite many countries implementing strict social distancing and hygienic preventive measures. Widespread vaccination is essential to curb the spread of the pandemic. However, because of the benefits of herd immunity, a vaccine is most effective if a large majority of the population accepts and uses it.

Public vaccine hesitancy is a large public health issue in general. However, especially in the case of the COVID-19 vaccine, concern about the safety of the vaccine due to the shortened research and testing period and the effectiveness of the vaccine due to the mutations of the virus further fuel hesitance towards a COVID-19 vaccine. Moreover, misinformation and conspiracy theories lead to misinformation and the erosion of trust.

In this paper, we conduct a message experiment using a representative random sample of over 4,000 households in Accra, Ghana, based on the latest Ghana Living Standard Survey (GLSS7). The experiment tests different messages about vaccinating against COVID-19 in July, where vaccines have become partially available in the country to certain groups. Participants are randomized into one of eight treatment arms or the control arm. We will analyze the impact of the messages on (i) the general perceived importance of the vaccine, (ii) the reported willingness to get the vaccine, (iii) the reported willingness to get the vaccine – even when a person has to pay for it, (iv) the reported willingness to get the vaccine via lottery, (v) the reported willingness to get the vaccine – when a person gets monetary compensation for the vaccine, and (vi) the urge for a vaccine mandate.

We contribute to the current literature by first providing evidence on COVID-19 vaccine attitudes at the start of the COVID-19 vaccine campaign; therefore, reducing the uncertainty people had about the safety and effectiveness of the vaccine in studies half a year ago. Second, since attitudes are highly country-specific, we can provide first empirical evidence for Ghana. Third, our experiment includes the poorest population and thus provides new insights into the population which research assumes has the lowest knowledge and the most hesitancy with respect to vaccines. Moreover, the poor are highly affected by the COVID-19 pandemic and it is essential to better understand the most vulnerable in a society. Fourth, the experiment is conducted based on a phone survey, enabling us to directly contact the participants and avoid biases due to access to the internet or due to illiteracy – which is very likely when including the poorest households. Lastly, since this experiment is part of a larger research project, we can not only measure the effect of a message but can also contribute to the current literature about factors associated with the intention to get COVID-19 vaccine. Besides socioeconomic factors, additional covariates will be added to the model, i.e. COVID-19 knowledge, following hygienic and social distancing measures, COVID-19 experience, trust in government, citizens, media, and science, general vaccine attitude, and information sources.

External Link(s)

More information about the larger research project

Registration Citation

Citation

Asiedu, Edward, Kathrin Durizzo and Isabel Günther. 2021. "Persuasive Messages for COVID-19 Vaccine Uptake: a Randomized Controlled Trial." AEA RCT Registry. July 06. https://doi.org/10.1257/rct.7864-1.0

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Experimental Details

Interventions

Intervention(s)

The intervention consists of eight different messages, read out loud by the enumerators on the phone right before the primary and secondary outcome variables are collected. It is part of a larger phone survey project, including questions about protective behavior, food security, participants' economic situation, health and mental health, and COVID-19 related questions. The eight different messages and the control group consisting of:
0. Control – no message
1. Message about efficacy
2. Message about safety
3. Message about role models – president
4. Message about role models – religious leaders
5. Message emphasizing scientific information source
6. Message with personal story
7. Social norm message
8. Community message
Randomization is done at the individual level. At the end of the survey, official Ghana Health Service recommendations for the COVID-19 vaccine are read out loud to all participants.

Intervention Start Date

2021-07-12

Intervention End Date

2021-08-31

Primary Outcomes

Primary Outcomes (end points)

a. Reported intention to get COVID-19 vaccine. [Time Frame: Immediately after the intervention, in the same survey in which the intervention message is provided ]

Primary Outcomes (explanation)

a. This is a self-reported outcome, elicited immediately after the intervention message, asking to what extent they agree with the following statement: “Once a COVID-19 vaccine is available in Ghana for me, I want to get it” (scale: strongly agree, somewhat agree, undecided, somewhat disagree, strongly disagree). In the analysis, responses among the eight different intervention arms and the control arm will be compared.

Secondary Outcomes

Secondary Outcomes (end points)

b. Reported personal importance attached to the COVID-19 vaccine. [Time Frame: Immediately after the intervention, in the same survey in which the intervention message is provided ]
c. Reported intention to get the COVID-19 vaccine – if the vaccine is not available for free. [Time Frame: Immediately after the intervention, in the same survey in which the intervention message is provided ]
d. Reported intention to get the COVID-19 vaccine – if to receive a compensation. [Time Frame: Immediately after the intervention, in the same survey in which the intervention message is provided ]
e. Reported intention to get the COVID-19 vaccine – if the person will join a lottery. [Time Frame: Immediately after the intervention, in the same survey in which the intervention message is provided ]
f. Agreement for a vaccine mandate [Time Frame: Immediately after the intervention, in the same survey in which the intervention message is provided ]

Secondary Outcomes (explanation)

b. This is a self-reported outcome, elicited immediately after the intervention message, asking to what extent participants agree with the statement (scale: strongly agree, somewhat agree, undecided, somewhat disagree, strongly disagree). In the analysis, responses among the eight different intervention arms and the control arm will be compared.
c. This is a self-reported outcome, examined immediately after the intervention message, asking to what extent they agree with the statement (scale: strongly agree, somewhat agree, undecided, somewhat disagree, strongly disagree). In the analysis, responses among the eight different intervention arms and the control arm will be compared.
d. This is a self-reported outcome, examined immediately after the intervention message, asking to what extent they agree with the statement (scale: strongly agree, somewhat agree, undecided, somewhat disagree, strongly disagree). In the analysis, responses among the eight different intervention arms and the control arm will be compared.
e. This is a self-reported outcome, examined immediately after the intervention message, asking to what extent they agree with the statement (scale: strongly agree, somewhat agree, undecided, somewhat disagree, strongly disagree). In the analysis, responses among the eight different intervention arms and the control arm will be compared. Additionally, the willingness to accept will be analyzed for the pooled for the intervention and control arm only comparing the differences among the four choices.
f. This is a self-reported outcome, examined immediately after the intervention message, asking “Do you think the vaccine should be made mandatory for everybody?” (scale: Yes, Not sure, No). In the analysis, responses among the eight different intervention arms and the control arm will be compared.

Experimental Design

We use a randomized controlled trial to study the impact of a message on (i) the general perceived importance of the vaccine, (ii) the reported willingness to get the vaccine, (iii) the reported willingness to get the vaccine – even when person has to pay for it, (iv) the reported willingness to get the vaccine via a lottery, (v) the reported willingness to get the vaccine – when person gets monetary compensation for the vaccine, and (vi) the desire to see a vaccine mandate. Until now, there is little evidence on how to improve COVID-19 vaccine attitudes a) at the start of a COVID-19 vaccine campaign, b) in an LMIC, specifically Ghana, c) among the poorest population where vaccine hesitancy is expected to be the highest, and d) by approaching participants directly by phone, avoiding bias due to illiteracy or use of specific information sources. Randomization allows us to test both the impact of the messages and the differences among monetary incentives for the respondents along with the vaccine distribution.
We use a representative random sample of over 4,000 urban households in Accra, Ghana, based on the latest Ghana Living Standard Survey (GLSS7). We randomize 4,050 participants into eight treatment arms and one control arm (with 450 participants each). Additionally, for the outcome about “willingness to accept the vaccine for payment”, four different monetary values will be randomly displayed among all treatment and control arms. In this way, we are able to compare not only the impact of the messages but also of monetary incentives.
The treatment messages contain messages (1) about efficacy, (2) about safety, (3) about role models – the president, (4) about role models – religious leaders, (5) scientific information source, (6) with a personal story, (7) about social norms, and (8) from the community. The control group does not receive any message – but answers the exact same survey. All respondents will receive the official Ghana Health Service recommendations read out loud by the enumerator.

Experimental Design Details

Randomization Method

randomization done in the office by a computer

Randomization Unit

individual

Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters

Sample size: planned number of observations

4050 observations

Sample size (or number of clusters) by treatment arms

450 observations by treatment arm

Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

For all outcomes, we use a beta (power) of 0.8, an alpha (significance level) of 0.05, a one-tailed test, and a proportion of outcome variance explained by level 1 covariates of 0.2. The proportion of the study population that would agree to a vaccine is 70% and was taken from our previous survey round in March 2021. Calculations were done using the 3ie Sample Size and Minimum Detectable Effect Calculator. The primary outcome “willingness to get the vaccine” is powered to detect a minimum effect of 0.075 (std. dev = 0.45, mean at baseline = 0.7).

Supporting Documents and Materials

IRB