Thymosin alpha 1 as an adjunct to influenza vaccination in the elderly: rationale and trial summaries

From a clinical perspective, the immune deficiency of aging (immune senescence) is not profound. In fact, it may be of little clinical consequence. However, older people are prone to chronic and debilitating disorders which alone, or in concert with the medications used in their treatment, may add to the age effect and create a more clinically relevant immune deficiency. As a result, many older people are susceptible to infection. Furthermore, it is now well recognized that older people respond less well to immunization protocols. Protection against influenza by vaccination with hemagluttinin is the prototype example. Despite programs that have raised vaccination rates dramatically over the past three decades, influenza remains a major cause of morbidity and mortality in the elderly. This, in part, is due to the fact that vaccine responses are reduced in older recipients. Strategies are under development to enhance vaccine efficacy in this population and one such strategy is the adjuvant use of thymosin alpha 1 (Talpha1). In both animal experiments and human trials, there has been demonstrated enhancement of vaccine responses. The findings to date warrant additional efforts to further examine the role of Talpha1 in augmenting specific vaccine responses both in the elderly or in younger subjects in situations in which there are suboptimal quantities of immunizing antigen available.