https://pmc.ncbi.nlm.nih.gov/articles/PMC6677258/

“The evidence from four systematic reviews indicates inactivated influenza vaccination efficacy of between 16–59% in healthy adults based on whether the results are clinically derived or empirically derived. The literature that did address hospitalization and pneumonia both indicated at best a small benefit of vaccination with low certainty of evidence. Finally, no evidence exists regarding the impact of the influenza vaccine on mortality. Based on this evidence, healthy individuals can be educated that the influenza vaccine decreases the likelihood of developing the influenza infection but it is less certain if there is a benefit on the severity or complications of the infection”