Vaccine effectiveness against influenza A in older adults and the effect of chronic conditions: results from the I-MOVE and VEBIS multicentre European hospital case–control studies, 2015/16–2023/24

Pooled-season results suggest low-moderate VE against influenza A subtypes among older SARI patients; higher against A(H1N1)pdm09 than A(H3N2), with little evidence of chronic condition modifying effect, apart from kidney disease and immunosuppression. We stress the importance of developing improved influenza vaccines for specific populations, and encourage further research into the effect of chronic conditions on IVE in older adults.