Background: Vaccination is key for mitigating the impact of recurring seasonal influenza epidemics. Despite the efficacy and safety of influenza vaccines, achieving optimal vaccination uptake remains a challenge. This study aimed to explore the determinants of influenza vaccination uptake using data from Influweb, the Italian node of the InfluenzaNet participatory surveillance network, and to compare self-reported vaccination rates with data from official sources.

Methods This study utilizes a longitudinal dataset of self-reported vaccination statuses from Italian participants across the 2011-2021 flu seasons. Logistic regression models were used to identify factors associated with vaccination uptake, while vaccination coverage of the Influweb population was compared with national data. Post-stratification weights were applied to account for demographic differences between the Influweb sample and the general population.

Results The analysis reveals that individuals using public transport, those living with minors, and residents of the Islands macro-region are less likely to receive the influenza vaccination. On the other hand, university-educated individuals, and those on medication for chronic diseases are more likely to be vaccinated. Age also plays a role: individuals aged 44 and under are less likely to vaccinate compared to those aged 45-65, while those over 65 are more likely to do so. Furthermore, higher cumulative influenza-like illness incidence rates within a macro-region are associated with increased vaccination uptake, suggesting that local epidemic dynamics may influence individual decisions. Finally, the impact of COVID-19 pandemic was associated with an increase in influenza vaccination uptake. Comparison of the Influweb data to nationally reported vaccination rates revealed higher coverage for self-reported vaccination. This could be linked to the voluntary nature of the survey, possibly attracting a more health-conscious cohort.

Conclusions Our study found that individuals living with minors and those relying on public transportation have lower odds of being vaccinated, despite having a higher documented risk of respiratory virus exposure. These findings highlight the importance of continued public health efforts targeting vulnerable groups and raising awareness about the risks of forgoing vaccination. The complex interplay of socioeconomic, demographic, and public health context significantly shapes vaccination decisions, emphasizing the need for tailored public health campaigns.

The authors have declared no competing interest.

The authors acknowledge support from the Lagrange Project of the Institute for Scientific Interchange Foundation (ISI Foundation) funded by Fondazione Cassa di Risparmio di Torino (Fondazione CRT). MM and DP acknowledge funding from the EU Commission in the framework of the EU Horizon Project VERDI (101045989). MM and DP acknowledge support by the ESCAPE project (101095619), funded by the European Union. DP and MM acknowledge support from the EU Commission in the framework of the EU Horizon Project SIESTA (101131957). Views and opinions expressed are however those of the authors' only and do not necessarily reflect those of the European Union or the Health and Digital Executive Agency. Neither the European Union nor the granting authority can be held responsible for them.

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