Photo taken on Feb. 19, 2021 shows a closed COVID-19 vaccine center in Frisco, Texas, the United States. U.S. COVID-19 vaccine rollout has been hindered by power outages amid the ongoing winter storms in much of the country, with nearly all states experiencing shipment delays. (Photo by Dan Tian/Xinhua)

Photo taken on Feb. 19, 2021 shows a closed COVID-19 vaccine center in Frisco, Texas, the United States. U.S. COVID-19 vaccine rollout has been hindered by power outages amid the ongoing winter storms in much of the country, with nearly all states experiencing shipment delays. (Photo by Dan Tian/Xinhua)

Photo taken on Feb. 19, 2021 shows a closed COVID-19 vaccine center in Frisco, Texas, the United States. U.S. COVID-19 vaccine rollout has been hindered by power outages amid the ongoing winter storms in much of the country, with nearly all states experiencing shipment delays. (Photo by Dan Tian/Xinhua)