Former Dallas Cowboy and Football Hall of Famer Emmitt Smith shakes hands with a COVID-19 vaccine recipient during a tour of vaccination site at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden greets Rep. Eddie Bernice Johnson, D-Texas, as she arrives at Love Field Airport in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden and Doug Emhoff attend a COVID-19 vaccination event at Minute Maid Park, in Houston, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden and second gentleman Douglas Emhoff wave at the media after a tour at a Houston Astros' COVID-19 vaccination event, Tuesday, June 29, 2021, at Minute Maid Park in Houston. The Astros, in partnership with Houston Methodist, hosted free vaccinations to the public. (Yi-Chin Lee/Houston Chronicle via AP)

First lady Jill Biden and former Dallas Cowboy and Football Hall of Famer Emmitt Smith tour a vaccination site at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden and former Dallas Cowboy and Football Hall of Famer Emmitt Smith tour a vaccination site at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden speaks at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden sits with military members and first responders as they attend a baseball game between the Houston Astros and the Baltimore Orioles at Minute Maid Park, in Houston, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden and Doug Emhoff, left, attend a COVID-19 vaccination event at Minute Maid Park, in Houston, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden and former Dallas Cowboy and Football Hall of Famer Emmitt Smith tour a vaccination site at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden and Doug Emhoff pose for a photo as they attend a COVID-19 vaccination event at Minute Maid Park, in Houston, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden and Doug Emhoff sit with military members and first responders as they attend a baseball game between the Houston Astros and the Baltimore Orioles at Minute Maid Park, in Houston, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden and Doug Emhoff talks to members of the media after they toured a COVID-19 vaccination event at Minute Maid Park, in Houston, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden speaks at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden greets Doug Emhoff as she arrives at William P. Hobby Airport in Houston, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

Former Dallas Cowboy and Football Hall of Famer Emmitt Smith speaks at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

First lady Jill Biden speaks at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. (AP Photo/Carolyn Kaster, Pool)

Former Dallas Cowboy and Football Hall of Famer Emmitt Smith talks with a COVID-19 vaccine recipient during a tour of vaccination site at Emmett J. Conrad High School in Dallas, Tuesday, June 29, 2021. First lady Jill Biden looks on at right. (AP Photo/Carolyn Kaster, Pool)