The risks and consequences of receiving or not receiving a vaccine can be hard to grasp. People therefore often unconsciously rely on mental strategies to understand vaccine information and make a decision. These strategies may lead to errors of judgement. “We believe that a highly relevant error of judgment is being overlooked in vaccine communication,” says Communication Scientist Lisa Vandeberg, who conducted the research study with her colleagues Gijsje Maas and Anita Eerland. “We know that people have more difficulty processing information about events that do not happen than about events that do. In the case of vaccines, this means that consequences that do take place (it made me ill, I experienced all kinds of side effects) are remembered more clearly and considered more important than information about consequences that do not take place (nothing bad happened).”
Consequences for vaccine communication
In research, this error of judgement is known as the ‘Feature Positive Effect’. The researchers believe that this has potentially important implications for vaccine communication. Vandeberg: “The effect of a vaccine is usually explained in terms of things that will not happen: people will not become ill, there will be no pandemic, one hundred thousand people will not die. While vaccine-critical posts – for example on social media and other platforms – often link vaccines to things that do happen: people do sometimes become ill, suffer side effects, or die. We thought that this might make a big difference.
Vandeberg, Maas and Eerland presented 350 participants with a fictional news story about a dangerous non-existent virus for which a vaccine had been found, followed by 16 headlines playing on the presence and absence of consequences of receiving the vaccine. Participants were asked which headlines they remembered, and which were important to them in forming an opinion about the vaccine. The results were crystal clear: present effects – whether negative (fever) or positive (feeling safe) – were remembered better and considered more important in assessing the vaccine than absent effects (no fever or not feeling safe).
The results of the study help explain the appeal of vaccine-critical information. At the same time, they provide concrete and practical directions for improving vaccine communication. Vandeberg: “Emphasise what does happen as a result of a vaccine (e.g. promote health), rather than what does not happen (no illness).”