PFAS Exposure and Immune Response to Vaccination in Adults

This clinical trial aims to investigate how exposure to Perfluorononanoic acid (PFNA), a type of per- and polyfluoroalkyl substance (PFAS), affects the immune response to the standard tetanus and diphtheria (Td) vaccine. The study focuses on participants from a community with known prior PFNA exposure through contaminated drinking water. The main question it aims to answer is: * Does exposure to PFNA weaken the body's initial immune response, leading to lower levels of protective antibodies after vaccination? Participants will: * Receive Tetanus and Diphtheria (Td) booster vaccination * Visit the study office 7 times over a 30-day period * Have blood and saliva collected at each study visit