With vaccination fatigue growing and the emergence of new coronavirus variants a possibility, health officials face a potential challenge when it comes to encouraging the public to get regular boosters to protect them against COVID-19.

Against this backdrop, researchers from the Medical University of Vienna (MedUni Vienna) teamed up with colleagues from the University of Vienna and the University of Perugia in Italy to assess the factors behind the drop in people's willingness to get vaccinated, including—for the first time—among those who have already received at least one dose. Intended as specialized recommendations for the design of effective vaccination drives, the findings were published in Nature Medicine.

In order to pinpoint the reasons behind the rise in COVID-19 vaccine fatigue and look into potential countermeasures, a research team headed by Tanja Stamm from the Section for Outcomes Research at MedUni Vienna conducted surveys using representative population samples in Austria and Italy.

The 6,357 survey participants were presented with a range of future scenarios that included random variables such as the availability of new and adapted vaccines, different forms of communication, costs, positive incentives (e.g. rewards or vouchers), the appearance of new coronavirus variants, and legal regulations (including for vaccination certificates and compulsory vaccinations).

Vaccination status makes a difference

The findings show that people's willingness to receive vaccinations is not influenced by a uniform set of factors—in contrast, these factors can be split into subgroups based primarily on current vaccination status. According to the study, people who have not received the COVID-19 vaccine at all have little confidence in political and social institutions, and are the least willing to be vaccinated.

These respondents indicated that they would refuse the vaccine in virtually all of the scenarios they were asked about, and only campaigns that highlighted the need for all members of society to pull together to combat the pandemic would have a small positive impact on their vaccine uptake.

Pandemic fatigue was very high among people who had received at least one or two vaccine doses and they reported average degrees of readiness to have additional boosters. However, the researchers found that this group was far more likely to be persuaded to have a booster shot through positive incentives (including rewards and vouchers).

People who have had three or more COVID-19 vaccinations were the most willing to receive boosters. For this group, the key determinants were the availability of adapted vaccines, low-barrier access to vaccinations, and the expert consensus on recommended vaccinations.

Positive incentives for individual target groups

"In view of these findings, we recommend offering adapted vaccines at different times of year, retaining low-threshold access to vaccinations and ensuring that people take experts' views into account in order to maintain high levels of immunization among the population in future," explained Tanja Stamm, who headed the study. Increased pandemic and vaccination fatigue goes hand in hand with a drop in the effectiveness of communication campaigns designed to encourage people to get vaccinated against COVID-19.

In the future, such campaigns could be replaced by institutional measures, including positive incentives aimed at specific target groups. The authors also found that steps should be taken to boost confidence in politicians, the health service and science in the long term. "In addition, the results of this study could provide decision makers and officials with guidance on future strategies, for example in autumn," Stamm concluded.