Oral Water Hydration to Prevent Post-Vaccination Presyncope

Subjects in the hydration group will be allowed up to 15 minutes to drink up to 500 milliliters (mL) of water prior to the vaccines. Subjects will be encouraged to drink the entire 500 mL; however, they are free to drink as much as they want and can finish before the end of the 15-minute period. Subjects will be instructed not to share the water and to not otherwise empty the bottle. As with the control group, subjects will be instructed not to eat or drink anything else for the duration of the study, unless clinically indicated (e.g., as part of management of presyncope or syncope).