Dr. Rochelle Walensky discusses the CDC investigating more than 300 cases of myocarditis after receiving the COVID-19 vaccine and how concerned people should be about the contagious Delta variant. READ MORE: https://abcn.ws/3vFH7VX SUBSCRIBE to GMA's YouTube page: https://bit.ly/2Zq0dU5 VISIT GMA's homepage: https://www.goodmorningamerica.com FOLLOW GMA: TikTok: tiktok.com/@gma Facebook: facebook.com/GoodMorningAmerica Twitter: twitter.com/gma Instagram: instagram.com/goodmorningamerica #COVID #Vaccines #DeltaVariant #Myocarditis #GMA