The Inverse Relationship between Influenza Vaccination and Antimicrobial Resistance: An Ecological Analysis of Italian Data

Antimicrobial resistance (AMR) is one of the key threats to global health and requires sustainable and effective actions to reduce its consequences in the near future worldwide. There are several well-documented and epidemiologically supported examples that both bacterial and viral vaccines might have an impact on AMR. Here, we conducted an ecological analysis of Italian data to evaluate the relationship between influenza vaccination coverage and AMR proportions over the last two decades. We found significant negative correlations between influenza vaccination coverage in the population over 64 years and AMR in Escherichia coli and Klebsiella pneumoniae isolates. The observed inverse relationships were confirmed by linear regression analysis. Similar results were obtained for the vaccination coverage in the overall population. Despite the main limitations of our study, its findings suggested an inverse relationship between influenza vaccination coverage and AMR proportions over the years, which was in accordance with previous theories illustrating how influenza vaccination reduced antibiotic prescriptions. However, since our study did not allow for us to elucidate the mechanisms underpinning the observed relationship, more and better data on confounding and mediating factors should be considered in future research.