Vaccine Response

The aim of this observational study is to determine if and how kidney failure affects the development of protective immune responses following vaccination in patients on chronic dialysis. Researchers will compare the effectiveness of the influenza vaccine in inducing protective antibodies between hemodialysis patients and subjects without chronic kidney disease. Participants will: * Be enrolled at the time of influenza vaccination * Visit the clinic at 7, 14, 30, 60, and 120 days after vaccination * Be asked to provide relevant clinical information and a blood sample at each visit

The goal of this research is to learn more about ZADAXIN® (trade name; thymalfasin generic; Ta1 for short) and determine if Ta1 has any benefit in increasing the immune response to the COVID-19 vaccine. Ta1 has been shown to stimulate the immune system to fight infections. This research study will test the safety and possible harms of Ta1 when it is given to people at different dose levels before COVID-19 vaccination.

The ability of the vaccines today to generate a long-lasting protection against infections varies greatly from one vaccine to another. The yellow fever vaccine (YF-17D) is one of the most successful vaccines ever developed, having been administered to over 600 million people globally. A single vaccination is known to induce durable protection over several decades. In contrast, the quadrivalent influenza vaccine (QIV) generates an immunity that wanes quickly with no long-lasting protection. Currently, the duration of immune protection for new vaccines is difficult to predict during vaccine product development and can only be ascertained by a "wait and see" approach. This is due, in part, to the fact that some of the signals that activate a durable immune system protection remain unknown. This study aims to provide a better understanding of this problem by vaccinating willing participants with either the FDA-approved yellow fever vaccine or the quadrivalent influenza vaccine and collecting baseline and follow-up biologic samples to compare how the immune system reacts.