Assessment of humoral immune responses to repeated influenza vaccination in a multiyear cohort: a five-year follow-up.

The long-term effects of host factors on vaccine-elicited immune responses have not been well-studied, and the interactions of host factors with annual influenza vaccinations are yet to be explored. We analyzed data from a cohort of 386 individuals who received the standard-dose influenza vaccine and enrolled in multiple seasons (≥2) from 2016 to 2020. Our analyses indicated disparate vaccine-elicited immune responses between males and females in adults when they were repeatedly vaccinated for at least two seasons. Notably, we found interactive effects between age and BMI on overall immune responses, and between sex at birth and BMI in adults.