Each autumn, before influenza quietly gathers its strength, a narrow window opens for those who wish to meet the season prepared rather than caught off guard. The flu vaccine — reformulated each year to reflect how the virus has shifted — requires roughly two weeks to awaken the immune system's defenses, making timing as consequential as the act of vaccination itself. This annual ritual is not a confession of last year's failure but an acknowledgment of a fundamental truth: the threat moves, and so must our response to it.