Assessment of Communication Interventions on Vaccination Knowledge and Acceptance

The study design consists of an online survey. The questionnaire and the communication measures were developed in collaboration with the following partners: the Amsterdam Institute for Global Health and Development (AIGHD) in Amsterdam, the Netherlands, and CIDEIM (Centro Internacional de Entrenamiento e Investigaciones Médicas) in Cali, Colombia, based on the findings of the previous focus group studies and the subsequent quantitative study on the prevalence of knowledge about and acceptance of novel (flavivirus) vaccines and perceived barriers to vaccination among the general population in Germany and Colombia.

Potential participants will be invited to participate in the study by the panel provider Toluna via a link in an email. Individuals who express their willingness to participate will first be asked questions about their sociodemographic background, their vaccination status against TBE (Germany) or yellow fever (Colombia), as well as their perception of risk regarding TBE or yellow fever and the associated vaccinations.

Participants will then be randomly assigned in a 1:1:1 ratio to one of three study arms:

• Control group (in Germany, a vaccination check based on the COVID-19 vaccination check on infektionsschutz.de; in Colombia, an educational video about the yellow fever vaccination from the Colombian Ministry of Health)
• Intervention group 1: Information format A (website)
• Intervention group 2: Information format B (slideshow/carousel)

In both countries, the intervention formats are implemented in the same way; only the vaccination being addressed differs (TBE in Germany, yellow fever in Colombia).

Within the two intervention groups, A and B, there is also a second randomized assignment to a presentation of an established (inactivated vaccine or live vaccine) versus a novel vaccine technology ("NovaCarrier"). This second randomization ensures that the assignment to vaccine technologies within the respective formats is not systematically linked to other participant characteristics. It serves exclusively to explore possible effects of the vaccine technologies on attitudes and intentions and does not form the basis of the primary case number planning.

Participants who view the materials featuring the hypothetical novel vaccine technology are transparently informed at the end of the study that this is a hypothetical technology.

Following the intervention, all participants will complete an adapted Informed Choice questionnaire (Marteau et al., 2001), which assesses risk understanding, knowledge, attitudes, and intention to be vaccinated against TBE or yellow fever. Subsequently, risk perception is assessed again after viewing an informational piece, and finally, participantsare asked two open-ended questions about safety and information needs regarding vaccinations.

The drafted communication measures will first be tested in a pilot study (n = 150; 75 participants per country) in order to adjust the materials to be developed before the main study (n = 1,374; 687 participants per country) if necessary. For this pilot study, the same questionnaire as for the main study will be used, with the addition of three open-ended questions regarding the information formats. The pilot study is not intended for final hypothesis testing, but solely to optimize the informational materials to be tested and, if necessary, the survey questions.