Testosterone-Driven Modulation of Vaccine Efficacy: From Molecular Mechanisms to Clinical Outcomes

Vaccination remains one of the most effective strategies for preventing infectious diseases by priming the immune system to recognize and eliminate pathogens, thereby reducing morbidity and mortality. Traditionally, vaccine development and administration have followed a universal model with little regard for biological differences among recipients. However, emerging research suggests that biological sex may influence immune responses to vaccination, with hormones such as testosterone playing a key role. Testosterone has been shown to modulate immune function, potentially contributing to variation in vaccine efficacy and adverse effects between males and females. This literature review examines the relationship between testosterone levels and vaccine responses in humans, with the aim of assessing whether sex-based biological differences warrant a move toward more personalized vaccine strategies. By synthesizing findings from existing studies, this review seeks to address the central question: What is the effect of testosterone levels on vaccine administration in humans, and should vaccines be tailored based on sex?