High-dose influenza vaccination significantly reduced cardiovascular and respiratory hospitalizations in older adults. Published in Circulation, this pooled prespecified analysis from the FLUNITY-HD program integrated data from two pragmatic randomized trials comparing HD-IIV with SD-IIV in adults aged ≥65 years. The dataset included 466,320 participants, 23.1% of whom had a history of CVD.

HD-IIV lowered hospitalization for any CVD to 1.15% versus 1.24% with SD-IIV, corresponding to a relative vaccine effectiveness (rVE) of 6.6%. Respiratory hospitalizations occurred in 0.92% of HD-IIV recipients and 0.98% of SD-IIV recipients, with an rVE of 6.5%. The greatest benefit was seen for heart-failure hospitalizations, which occurred in 0.11% versus 0.15%, giving an rVE of 21.3%. Benefits were similar regardless of CVD history, with interaction p values >0.66 across outcomes.

HD-IIV provided broader cardiovascular and respiratory protection than SD-IIV in this large older population, with the most notable reduction observed in heart-failure–related hospitalization.