COVID-19 Messaging for Vaccination

Facebook, Inc., Code3, Stanford University, Harvard University, Yale University, Johns Hopkins University, Massachusetts General Hospital, Ludwig-Maximilians - University of Munich, National Institutes of Health (NIH)

This study will distribute videos of health professionals encouraging Covid-19 vaccination to a large sample of Facebook users, and will test the most effective ways to maximize diffusion of this vaccine-related content to increase vaccination rates. The study sample will be U.S. states where vaccination rates remained low in fall 2021. The experimental design is an RCT with 4 groups, randomized at the county level: 1) a control group which receives no intervention, 2) a treatment group in which Facebook users receive ads which include videos of health professionals telling them to get vaccinated, 3) a treatment group in which Facebook users receive ads which include videos of health professionals encouraging them to help their friends to get vaccinated, and 4) a treatment group in which Facebook users receive ads which include videos of health professionals encouraging them to get their most influential friends to help their friends get vaccinated. In treatments 3 and 4, participants will have the option to sign up to be a "vaccine ambassador," in which case they will get notifications when the study team posts new vaccine-related content, and will receive reminders about encouraging their friends to be vaccinated. The vaccine ambassadors will also be entered into a lottery to win prizes. The study team is building a website to host the videos of health professionals which answer common questions about Covid-19 vaccination. The investigators will measure engagement with the vaccine-related content as well as assess effects on vaccination rates at the county level.

The study will have three treatment arms and a control group. Each of the treatments will be randomized at the county level and will be initiated through a Facebook ad campaign. Experimental Sample: The experimental sample includes all states where less than 60% of the total population had received a first dose of Covid-19 vaccine by October 21, 2021. There are 1402 counties in the 19 states satisfying those criteria (Alabama, Alaska, Arkansas, Georgia, Idaho, Iowa, Indiana, Louisiana, Michigan, Mississippi, Missouri, Montana, North Dakota, Ohio, Oklahoma, South Carolina, Tennessee, West Virginia, Wyoming). Excluding the five counties with missing data, there are 1,397 counties in the experiment, of which there are 468 counties in the control group, 310 counties in T1 ("direct" messaging) treatment, 309 counties in T2 ("friends" messaging), and 310 counties in T3 ("gossips" messaging). The following procedures will be used: Treatment Group 1 ("Direct" messaging): The investigators will conduct a Facebook ad campaign to show content about COVID-19 vaccination to a large number of Facebook users. Facebook will allocate ad credits across users in treatment areas. The ads will be displayed twice per week for 3-4 weeks. Like for any Facebook ad, individuals can choose to whether or not to watch the video and can close the ad at any time. If individuals wish, they can also share any of the content with others. The videos shown in the ads will be hosted on our project Facebook page "Doctors for Coronavirus Prevention." As in previous projects by the investigators, a health professional (normally wearing a white coat or scrubs) will read very short scripts directly onto the camera (see eg. https://www.facebook.com/doctors4covidprevention/posts/104965558099200 for an example). Treatment Group 2 ("Friends" messaging): For this group, the Facebook ad campaign will recruit individuals to become "vaccine ambassadors" to help spread the word about vaccination to their friends, families and communities. Recruitment ads will be disseminated in a similar manner to the content in T1. Individuals will be able to share the ad with others. Individuals interested in learning more can click through a link in the ad to the vaccine ambassador webpage. Participants can consume or share any of the information on the webpage. Interested individuals can also enroll formally as vaccine ambassadors. They can share their contact information with the study to a) be entered into prize lotteries, b) receive reminders to share content with others, c) be contacted in the future for possible follow-up surveys. They will be asked to give their informed consent at this time and will be screened based on whether they live in a treated county and whether they are 18 years or older. Treatment Group 3 ("Gossips" messaging): This treatment looks the same as Treatment Group 2, except the recruitment ads will differ slightly. If the individual clicks through to learn more about vaccine ambassadors, they will also be reminded to share the invitation with people they know who are often the source of important news or information. Control: individuals in these counties will receive no intervention and will never be contacted by members of the study team. Treatment and control status at the county level will be merged with aggregated and de-identified datasets to measure COVID vaccinations, COVID symptoms, and cases, and engagement with the vaccine ambassador content. The study team will create a series of websites with materials that the vaccine ambassadors can share with friends, family and others in their communities. This same content will be disseminated through sponsored Facebook ads in T1. On the website, the framing of the vaccine-related videos with either a "fact" or "myth" frame will be randomized. The purpose is to study which framing is more effective at engaging users.

There are four arms in the study which geographic areas are assigned to in parallel. The geographic areas in the three treatment arms will receive a Facebook ad campaign over the same time period to one another.

No intervention in this arm; the study team will examine publicly available county- and zip code-level outcomes in this group.

Facebook users in the area receive ads which include videos of health professionals telling them to get vaccinated. The health professionals answer common questions about Covid-19 vaccines (e.g. are they safe / are they free).

Facebook users in the area receive ads which include videos of health professionals encouraging them to help their friends to get vaccinated. There is also a link in the ad to a website build by the study team. This website hosts videos which answer common questions about vaccination (the same videos which are directly served to Facebook users in Treatment 1).

Facebook users in the area receive ads which include videos of health professionals encouraging them to nominate their most influential friends to help their friends get vaccinated. The difference from Treatment 2 is that the health professionals call on Facebook users to get their most influential friends to do the convincing about the vaccine. There is also a link in the ad to a website built by the study team. This website hosts videos which answer common questions about vaccination (the same videos that are directly served to Facebook users in Treatment 1).

Receive ads on Facebook or through our website with videos in which health professionals tell people to get the Covid-19 vaccine. The health professionals answer common questions about the Covid-19 vaccine, such as how mRNA vaccines work, and what types of side effects to expect.

Receive ads on Facebook with videos in which health professionals tell people to encourage their unvaccinated friends to get the Covid-19 vaccine.

Receive ads on Facebook with videos in which health professionals tell people to get their most influential friends to encourage their unvaccinated friends to get the Covid-19 vaccine.

Adults in participating geographic areas can sign up to be a "vaccine ambassador" on a website that the study team has built. The study team will send updates to vaccine ambassadors when new content has been posted to the website (e.g. a new video) and/or to remind the vaccine ambassadors to encourage their friends to get vaccinated. The study team will incentivize vaccine ambassadors by entering participating ambassadors into a lottery for a prize.

The same videos will be displayed using two different frames: a "myth" frame and a "fact" frame. Visitors to the vaccine content website will randomly receive one framing of each video.

County-level Covid-19 vaccination rates were analysed using publicly available data. The number of new vaccinations in each county was transformed using the inverse hyperbolic sine because the underlying vaccination count data were right-skewed and included zeros. Larger numbers are considered better in the context of the study (more people vaccinated).

Inclusion Criteria: Facebook user Over 18 years old In a geographic area targeted by the study Exclusion Criteria: -

The investigators do not plan to share any individual participant data. The only individual participant data that the study will collect will be contact information through the "vaccine ambassador" program. "Vaccine ambassadors" are adults living in geographic areas assigned to Treatment 2 or Treatment 3 who have signed up on the study website to receive updates and reminders about vaccination-related content. However, the study team does not plan on collecting any information about the behavior of vaccine ambassadors, and so do not plan to share any of their data (which will just consisting of contact information) with other researchers.