An Extended Knowledge Intervention Addressing Vaccine Hesitancy in the Field: Results from Two Representative Surveys

Objective: Older adults may fail to demand vaccinations because they lack knowledge about the benefits of vaccination or underestimate disease risks. This study evaluated an extended knowledge intervention that provided information on lesser-known risks of influenza—including pneumococcal disease and sepsis—and the benefits of vaccination. Methods: The intervention was implemented in a model region in Germany during two influenza seasons. Two quota-sampled telephone surveys targeting adults 60+ were conducted to assess the impact of the intervention (N = 700 each). Quasi-experimental groups (intervention-exposed vs. non-exposed) were defined based on self-reported intervention exposure. Primary outcomes included knowledge (influenza, pneumococci, sepsis), the 5C antecedents of vaccination, and vaccination intention and behavior. Results: Intervention exposure had small positive effects on knowledge about influenza (η² = .009), pneumococci (η² = .012), and sepsis (η² = .004). It was also associated with higher risk–benefit calculation regarding influenza vaccination (η² = .003) and increased confidence in the safety of pneumococcal vaccination (η² = .020). Vaccination intentions for both diseases did not differ between groups. Although the intervention did not directly influence behavior, vaccination uptake increased over time due to external factors (influenza: OR = 1.880; pneumococci: OR = 2.080). Conclusions: Information alone can enable informed decisions and can help to change underestimated risks, but does not shift behavior. Embedding knowledge gains within multi-component strategies (e.g., provider endorsement, reminders, easy access) is the most plausible path to increased coverage. Targeting other factors is also important.