Those enrolled in the study will have about 2 tablespoons of blood drawn before vaccination with a standard tetanus/diphtheria booster shot. Volunteers who have previously been vaccinated with the hepatitis B vaccine and all blood transplant patients will also receive a hepatitis B vaccination. Participants will have blood drawn (from 1 to 5 tablespoons) up to once a week after vaccination for no more than 8 weeks to evaluate the immune response to vaccination.