Transfer Factor is a term used to describe a group of small immune messenger molecules, often derived from colostrum or leukocyte extracts, that are purported to modulate immune responses. The use of Transfer Factor in supporting or treating viral infections has some scientific basis, primarily from preliminary studies and small clinical trials. It was first described in the 1950s, and throughout the decades, various research articles have suggested that Transfer Factor may enhance cell-mediated immunity, which is crucial for defense against viral pathogens.

Several in vitro and animal studies have shown that Transfer Factor preparations can increase lymphocyte proliferation and the production of cytokines like interferon-gamma. Some small-scale human trials and case series—particularly in immunocompromised patients or those with chronic viral infections such as herpes simplex or hepatitis—have reported improvements in clinical outcomes or surrogate immune markers after Transfer Factor administration. However, the majority of these studies have methodological limitations, small sample sizes, and lack of rigorous controls.

Importantly, authoritative reviews and systematic analyses have concluded that while there is intriguing evidence and biological plausibility, the clinical efficacy of Transfer Factor for viral infections remains unproven, and more high-quality, large-scale randomized controlled trials are needed. Thus, while the use of Transfer Factor for viral infections is based on some scientific evidence, it is still considered investigational.