The Taming of the Flu - Spatial patterns of influenza-like illness and the challenges and opportunities in immunisation on a city level

Seasonal influenza is a preventable, often underestimated infectious disease. In Switzerland, it causes between 1,000 and 5,000 hospitalizations and about 400-1,500 deaths annually. Vaccination is the most effective strategy to reduce virus transmission and decreases the severity of influenza, number of complications and deaths. Yet, public confidence of influenza vaccines is decreasing which leads to reductions in vaccination rates thereby limiting its effectiveness. Community variation in attitudes, beliefs and behaviours about influenza vaccination have been identified as an important issue, as well as the lack of comprehensive assessment of community opinions and behaviours related to vaccination. For this study, which is part of a large interdisciplinary project funded by the Swiss National Science Foundation, we distributed 30,000 questionnaires (return rate 27.2%) in ten urban quarters of Basel, making this the largest survey on influenza undertaken so far in Switzerland. We aimed to understand (1) the spatial patterns of influenza-like illness (ILI) and vaccinated individuals within an urban context, and to determine which factors influence an individual’s likelihood of getting an ILI or being vaccinated, and (2) which factors may determine an individual’s willingness to be vaccinated and in what ways vaccination behaviour varies among different population groups. This study could show that there is high spatial variability of vaccinated and sick individuals. The main barriers towards an influenza vaccination seem to be false ideas about the vaccination, how the immune system works and many feel the flu is not dangerous enough to vaccinate against it. Studying influenza is useful as it can also help to understand other pandemics, such as the current Covid-19 pandemic.