Immunologic Response to FluMist vs. Flucelvax

This is a non-blinded, randomized controlled trial analyzing influenza vaccine immunogenicity response in children/adolescents/young adults aged 4-21 years given one of two FDA approved and licensed influenza vaccines: FluMist (live attenuated influenza vaccine by nasal administration) and Flucelvax (egg-free cell-culture inactivated influenza vaccine). This study will enroll about 440 healthy participants, about 220 per vaccine arm. Participants will be randomized in blocks of 4 using a 1:1 allocation to receive either FluMist or Flucelvax. Blood work will be conducted on all participants at baseline prior to vaccine receipt and post-vaccination at Day 7 (range 6-9 days) and Day 28 (range 21-35 days). The primary objective of the study is to determine pre- and post-serologic responses to each vaccine type.