Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, explains to Rachel Maddow what aspects of Covid-19 immunity are being researched now to find out if vaccine booster shots will be necessary at some point in the future.  » Subscribe to MSNBC: http://on.msnbc.com/SubscribeTomsnbc About The Rachel Maddow Show: Through her unique approach to storytelling, Rachel Maddow provides in-depth reporting to illuminate the current state of political affairs and reveals the importance of transparency and accountability from our leaders. Maddow seeks to explain our complex world and deliver news in a way that's illuminating and dynamic, connecting the dots to make sense of complex issues. Maddow also conducts interviews with individuals at the center of current news stories to provide important perspective. MSNBC delivers breaking news, in-depth analysis of politics headlines, as well as commentary and informed perspectives. Find video clips and segments from The Rachel Maddow Show, Morning Joe, Meet the Press Daily, The Beat with Ari Melber, Deadline: White House with Nicolle Wallace, Hardball, All In, Last Word, 11th Hour, and more. Connect with MSNBC Online Visit msnbc.com: http://on.msnbc.com/Readmsnbc​ Subscribe to MSNBC Newsletter: http://MSNBC.com/NewslettersYouTube​ Find MSNBC on Facebook: http://on.msnbc.com/Likemsnbc​ Follow MSNBC on Twitter: http://on.msnbc.com/Followmsnbc​ Follow MSNBC on Instagram: http://on.msnbc.com/Instamsnbc​ #MSNBC #Fauci #CovidVaccine