Icon arrays reduce concern over COVID-19 vaccine side effects: a randomized control study

Abstract

On April 13, 2021, the CDC announced that the administration of Johnson and Johnson's COVID-19 vaccine would be paused due to a rare blood clotting side effect in ~ 0.0001% of people given the vaccine. Most people who are hesitant to get a COVID-19 vaccine list potential side effects as their main concern (PEW, 2021); thus, it is likely that this announcement increased vaccine hesitancy among the American public. Two days after the CDC's announcement, we administered a survey to a group of 2,046 Americans to assess their changes in attitudes toward COVID-19 vaccines. The aim of this study was to investigate whether viewing icon arrays of side effect risk would prevent increases in COVID-19 vaccine hesitancy due to the announcement. We found that using icon arrays to illustrate the small chance of experiencing the blood clotting side effect significantly prevented increases in aversion toward the Johnson and Johnson vaccine as well as all other COVID-19 vaccines.

Fig. 1

An icon array illustrating the 1 (red dot) in 900 chance of experiencing a side effect due to a treatment. The icon array in Experiment contained 1 million dots, one of them red, that participants had to scroll through if assigned to a visualization condition. The arrow on the right represents how participants had to scroll through the array of dots, but this arrow was not part of the original figure

Fig. 2

Change in Aversion toward the J&J and all COVID-19 vaccines by experiment and condition. a, b Mean and standard error change in vaccine aversion by condition in Experiment 1. Notice that the data are displayed as overlapping distributions. Point color indicates probability expression group (see legend). c, d Mean and standard error change in vaccine aversion by condition in Experiment 2. Note that while the y-axes above range from 0.25 to 0.75, the full range was 0 to 1 and that the data are displayed as stacked distributions

Fig. 3

Relative risk, where 1 (red dot) in 900 experiences a side effect and 1 (green) in 20 lives is saved by the treatment. The relative-risk icon array in Experiment 2 contained 1 million dots that participants had to scroll through if assigned to a visualization condition. The arrow on the right represents how participants had to scroll through the array of dots, but this arrow was not part of the original figure