A study published today in eLife has shown.
The research could help inform public health campaigns aimed at increasing uptake of COVID-19 booster shots, which are currently far from target levels.
The study was conducted in the US and the UK, where vaccination rates have fallen and only 63.9% and 71.3% of the respective populations are fully vaccinated. Additionally, just over 27% and 55% of adults have had their booster shots in the US and UK, respectively.
“Vaccine hesitancy is not the result of a single common cause and can vary for different people and populations,” explains lead author Nikkil Sudharsanan, assistant professor of behavioral sciences for disease prevention and health care at the Technical University from Munich, Germany. “A common fear surrounding COVID-19 vaccination is concern about side effects, heightened by widespread media coverage that failed to put the very low risk of side effects in context with other risks, such as the likelihood of death from COVID-19 itself. Addressing these public concerns will be a key component of efforts to improve vaccine use in the US, UK and around the world, especially with recommendations for booster doses underway.”
Evidence shows that the way risks are framed and presented to people can affect their perceptions of risk severity and ultimately their behaviour. So the researchers set out to compare different ways of framing the risk of a hypothetical COVID-19 vaccine, and then asked participants if they would get vaccinated and how safe they thought it was.
They designed an online randomized controlled trial, which provided vaccine information to 8,988 people aged 18 years and older in the UK and US. Participants were presented with information about the hypothetical vaccine, including the risk of serious blood clots, framed in three different ways: 1) with an additional label explaining whether the risk is low or high, 2) adding a comparison risk, such as the risk of dying in a motor vehicle, and 3) whether the risks were reported as absolute (ie, presenting the actual risk of vaccine side effects together with other common risks) or relative (presenting the risk of vaccine side effects as a multiple of other common risks).
They found that adding a simple qualitative risk level of “very low risk” next to the vaccine side effect increased people’s intentions to get vaccinated by 3 percentage points. Similarly, adding a comparison to motor vehicle fatality rates increased intentions by 2.4 percentage points. These framing tools worked even better when used together: they increased vaccination intentions by 6.1 percentage points.
The authors also report some surprising results: Comparing vaccine side effect rates with COVID-19 mortality rates did not appear to influence vaccine intentions. This was unexpected because COVID-19 death rates are substantially higher than motor vehicle death rates (170 per 100,000 versus 12 per 100,000 in the US) and it is a cause of death directly associated with the purpose of vaccination strategies against COVID-19. A second surprise was that expressing risk as relative versus absolute had no apparent impact on people’s willingness to receive the hypothetical vaccine.
“We believe that our results can inform communication efforts aimed at increasing vaccination, especially booster vaccinations,” concludes co-author Alain Vandormael, Senior Data Scientist, Heidelberg Institute for Global Health, University Hospital Heidelberg, Germany. “Our results focus on vaccination intentions and not vaccination rates, so the next step is to test whether these framing efforts can increase opportunity before translating our findings into policy action.”
Materials provided by eLife. Note: Content can be edited for style and length.
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