This December 2020 photo provided by Yukon Kuskokwim Health Corporation, Village Service Chief Dr. Elizabeth Roll holds a COVID-19 vaccine in Napakiak, Alaska. Getting the vaccine to the world's farthest corners means delivering it by boat to Maine's islands, traveling by snowmobile to villages in Alaska and navigating complex waterways in Brazil's Amazon. (Yukon Kuskokwim Health Corporation via AP)

People wait in line to get vaccine against coronavirus, at a night club turned into a mass vaccination center in Stockholm, Sweden, Friday April 16, 2021. (Carl-Olof Zimmerman/TT News Agency via AP)

President Joe Biden speaks about Russia in the East Room of the White House, Thursday, April 15, 2021, in Washington. (AP Photo/Andrew Harnik)

FILE - In this Feb. 15, 2021 file photo, a healthcare worker prepares a dose of the CoronaVac COVID-19 vaccine at the Salvador Sanfuentes public school during the start of the nationwide vaccination campaign for educators, in Santiago, Chile. A real-world study of millions of Chileans who had received the Chinese-developed CoronaVac vaccine has found it 67% effective against symptoms and 80% against death from COVID-19, the South American country's Health Ministry said Friday, April 16, 2021. (AP Photo/Esteban Felix, File)

German Chancellor Angela Merkel arrives for a parliament session about a new law to battle the coronavirus pandemic at the parliament Bundestag in Berlin, Germany, Friday, April 16, 2021. (AP Photo/Markus Schreiber)

In this image made from video, Australian Prime Minister Scott Morrison, right, with Australian Chief Medical Officer Paul Kelly, speaks during a news conference in Canberra, Australia, Thursday, April 8, 2021. Australia on Thursday become the latest country to restrict use of the AstraZeneca vaccine by recommending that it not be given to people under age 50. (SBS via AP)

Police officers stand in front of the Reichstag building during a rally against the Corona measures as lawmakers discuss a federal new controversial law to fight the pandemic in Berlin, Germany, Friday, April 16, 2021. (Christoph Soeder/dpa via AP)

Australia's Health Minister Greg Hunt discusses the COVID-19 vaccination program at a press conference at Parliament House in Canberra, Friday, April 9, 2021. The Australian government has decided, Tuesday, April 13, 2021, against buying the single-dose Johnson & Johnson coronavirus vaccine as a way to accelerate its immunization program. (Mick Tsikas/AAP Image via AP)

Palestinian worshipers pray during the first Friday of the holy month of Ramadan at the Al Aqsa Mosque compound in Jerusalem's old city, Friday, April. 16, 2021. Tens of thousands of Muslim worshippers have gathered at a sacred Jerusalem plaza for the first Friday prayers of Ramadan after coronavirus lockdowns kept the site off-limits last year. About 70,000 faithful, most of them Arab citizens of Israel, prayed in al-Aqsa mosque, the third holiest site in Islam. (AP Photo/Mahmoud Illean)

French President Emmanuel Macron, left, welcomes Ukrainian President Volodymyr Zelenskyy at the Elysee palace in Paris, Friday, April 16, 2021. Ukrainian President Volodymyr Zelenskyy is holding talks with French President Emmanuel Macron and German Chancellor Angela Merkel amid growing tensions with Russia, which has deployed troops at the border with the country. (AP Photo/Lewis Joly)

FILE - In this Dec. 8, 2020, file photo Dr. Vivek Murthy, who has been nominated to be U.S. Surgeon General speaks during an event at The Queen theater in Wilmington, Del. The Senate has confirmed Murthy as surgeon generral on March 23, 2021. (AP Photo/Susan Walsh, File)

Helpers test a woman at a test center for the novel corona virus using a rapid test in Hannover, Germany, Friday, April 16, 2021. The Robert Koch Institute (RKI) continues to report an increase in new corona infections in Germany. (Julian Stratenschulte/dpa via AP)

Italian Premier Mario Draghi meets the media during a news conference to illustrate the government's new measures to cope with COVID-19 pandemic, in Rome, Friday, April 16, 2021. (Remo Casilli/Pool via AP)

City streets wear a deserted look following lockdown to curb the spread of coronavirus in Dhaka, Bangladesh, Wednesday, April 14, 2021. Bangladesh is enforcing a lockdown shutting shopping malls and transportation, to help curb the spread of coronavirus as the rate of infections and deaths have increased in recent weeks. (AP Photo/Mahmud Hossain Opu)

In a photo provided by the Michigan Office of the Governor, Michigan Gov. Gretchen Whitmer addresses the state during a speech, Wednesday, April 14, 2021, in Lansing, Mich. The governor provided an update on COVID-19 cases, vaccines and variants and discussed the state's efforts to expand the use of monoclonal antibody therapy to help those diagnosed with COVID-19 avoid hospitalization. (Michigan Office of the Governor via AP)

A man passes doctors consulting rooms in Johannesburg Friday, April 16, 2021. South Africa took the first step to launch online registrations for the vaccination of people who are 60 years and older as it prepares for the second phase of its vaccination programme expected to start next month. (AP Photo/Denis Farrell)

California Gov. Gavin Newsom, left, grabs a flyer as Tiburcio Vasquez Health Center CEO Andrea Schwab-Galindo, right, looks on during a visit with staff members at the health center's vaccination site at Our Lady of the Rosary church in Union City, Calif., on Thursday, April 15, 2021. The state expanded vaccine eligibility to all Californians aged 16 and older on Thursday. (Anda Chu/Bay Area News Group via AP)

Kashmiris wait in queue to register themselves to test for COVID-19 in Srinagar, Indian-controlled Kashmir, Thursday, April 15, 2021. India's two largest cities imposed stringent restrictions on movement and one planned to use hotels and banquet halls to treat coronavirus patients amid a devastating surge that is straining a fragile health system. (AP Photo/ Dar Yasin)