The American Academy of Pediatrics is suing Health and Human Services Secretary Robert F. Kennedy Jr. over his changes to vaccines. Dr. Susan Kressley, the group's president, joins Katy Tur to share more on the lawsuit and why they were compelled to act, saying his actions "really crossed a line." For more context and news coverage of the most important stories of our day click here: https://www.msnbc.com/ » Subscribe to MSNBC: https://www.youtube.com/msnbc » Subscribe to MSNBC on TikTok https:/