The volunteers will be enrolled into two groups. Group A: Up to 30 healthy adult volunteers age 21-40 who will be given seasonal quadrivalent inactivated influenza vaccine (IIV4) prior to flu season for each of 5 years. They will also be given an inactivated Hepatitis A vaccine in the spring of years 1 and 2. Each volunteer will complete a total of 4 visits for each immunization: Day 0 (pre-immunization), Day 6-8, Day 12-15, and Day 26-30 (post-immunization). All visits will consist of drawing blood for study assays and monitoring for serious adverse events (SAEs).