Measuring the Impact of COVID-19 Vaccine Misinformation on Vaccination Intent in the UK and USA

"[I]n both countries, respondents were less likely to agree with, have trust in, fact check, share, or say that the information raised their vaccination intent when shown misinformation, as opposed to when they were shown factual information."

Widely circulating false information about the COVID-19 pandemic and vaccines on social media platforms, such as the myth that vaccine trial participants died after taking a candidate COVID-19 vaccine, can build on preexisting fears, seed doubt and cynicism, and threaten to limit vaccine uptake. Conducted in the United Kingdom (UK) and the United States (US), this randomised controlled trial (RCT) aimed to inform the design of communication around vaccination campaigns by quantifying how exposure to online misinformation around COVID-19 vaccines affects intent to vaccinate to protect oneself or others. In addition, the RCT sought to understand how misinformation differentially impacts sociodemographic groups and individuals according to their social media use or sources of trusted information.

For both the UK and the US, both the treatment and control groups were nationally representative samples by gender, age, and sub-national region. Among 8,001 participants, 3,000 UK and 3,001 US respondents were exposed to images of recently circulating online misinformation related to COVID-19 and vaccines (treatment group) and 1,000 respondents in each country were shown images of factual information about a COVID-19 vaccine to serve as randomised controls (control group). As misinformation can be highly country- and context-dependent, UK and US respondents were exposed to different sets of misinformation; factual information was the same for both groups. Through a methodology detailed in the article, the researchers assessed the causal impact of misinformation on vaccination intent on two vaccination motives: (i) to accept a COVID-19 vaccine to protect oneself, and (ii) to accept a COVID-19 vaccine to protect family, friends, and at-risk groups (this measure is particularly important in the UK and the US, where altruistic messaging prompts have been a feature of COVID-19 public health messaging campaigns).

The study found that, in both countries, as of September 2020, fewer people would "definitely" take a vaccine than is likely required for herd immunity: 54.1% of the public in the UK (95th percentile interval (PI) 52.5 to 55.7) and 42.5% in the US (95% PI 41.0 to 44.1) , and that, relative to factual information, recent misinformation induced a decline in intent of 6.2 percentage points (95% PI 3.9 to 8.5) in the UK and 6.4 percentage points (95% PI 4.0 to 8.8) in the US among those who stated they would definitely accept a vaccine.

In both countries, there was evidence that some sociodemographic groups are differentially impacted by exposure to misinformation, relative to factual information. For example, in the US, females are less robust to misinformation than males when considering vaccination intent to protect others. There is also evidence that lower-income groups are less likely to lower their vaccination intent to protect themselves or others upon exposure to misinformation than the highest-income group.

The researchers found no strong evidence to suggest that individuals in the UK or the US who use social media more frequently are more likely to lower their vaccination intent when exposed to misinformation compared with those in the control group. In the UK, individuals who trust celebrities for information about COVID-19 are more robust to COVID-19 misinformation than those who do not, whereas in the US, individuals who indicated trust in family or friends for such information are less robust than those who did not.

Finally, scientific-sounding misinformation was more strongly associated with declines in vaccination intent. Specifically, the misinformation images identified as having the strongest association with decreased vaccination intent presented a direct link between the COVID-19 vaccine and adverse effects and cited articles and scientific imagery or links to articles purporting to be reputable to strengthen their claim.

The researchers stress that this study does not replicate a real-world social media platform environment, where information exposure is a complex combination of what is shown to a person by the platform's algorithms and what is shared by their friends or followers. However, it highlights the need to directly quantify such social network effects and the challenges policymakers face to "undo" the impact misinformation may have already had, while clearly communicating messages about the safety, effectiveness, and importance of the vaccine.

In conclusion: "This analysis provides a platform to help us test and understand how more effective public health communication strategies could be designed and on whom these strategies would have the most positive impact in countering COVID-19 vaccine misinformation."