-
Now Playing: Herd immunity by September 'an ambitious goal': Dr. Vivek Murthy
-
Now Playing: Tributes pour in honoring broadcasting legend Larry King
-
Now Playing: All eyes on quarterback Patrick Mahomes as he's cleared from concussion protocol
-
Now Playing: Mystery lottery winner puts Novi, Michigan, on the map
-
Now Playing: Public health expert speaks on multiple new COVID-19 variants
-
Now Playing: ABC News' political analyst on President Biden's goals, progress
-
Now Playing: 20 million doses of the coronavirus vaccine have been administered in the US
-
Now Playing: One of 9 prosecutors in Trump's second impeachment trial speaks out
-
Now Playing: President Biden to continue pushing forth agenda, cabinet nominees
-
Now Playing: National Guard chief discusses troops staying in nation's capital
-
Now Playing: Tributes pour in on social media for Larry King
-
Now Playing: Grandma reunites with grandchildren after recovering from COVID-19
-
Now Playing: Drivers line up for COVID-19 vaccine in Alabama
-
Now Playing: Multiple storms to move across US
-
Now Playing: Larry King, talk show legend, dies at 87
-
Now Playing: Kansas City Chiefs' QB Patrick Mahomes speaks out about recovering from hard hit
-
Now Playing: Remembering baseball legend Hank Aaron
-
Now Playing: US sees highest weekly increase of COVID-19 cases in children since pandemic began
-
Now Playing: Mega Millions winning ticket sold in Michigan
-
Now Playing: How Biden's administration will increase COVID vaccine supply