Seven-year-old Mimi Meade winces from the sting as Dr. Richard Mulvaney inoculates her April 26, 1954 in McClean, Va., with the new Salk polio vaccine. Mrs. John Lucas, a registered nurse, holds Mimi's arm steady as she gets one of the first injections of the countrywide test. (Photo by Harvey Georges/AP Photo)

A motor taxi driver gets his hands washed at an Ebola screening station on the road between Butembo and Goma on July 16, 2019 in Goma. The first patient to be diagnosed with Ebola in the eastern DR Congo city of Goma has died, the governor of North Kivu province said on July 16, 2019. The case – the first in a major urban hub in the region's nearly year-old epidemic of the disease – has sparked deep concern in neighbouring Rwanda and at the UN. (Photo by John Wessels/AFP Photo)

Soldiers from the Nigerian Armed Forces take position and secure the streets in Lagos Island, Lagos, on February 27, 2023, after hoodlums had harassed market owners. Nigeria slowly counted more results on Monday after a tight election for the presidency of Africa's most populous nation as delays and accusations of manipulation fuelled tensions Nearly 90 million were eligible to vote on Saturday for a successor to President Muhammadu Buhari, with many hoping for a new leader to tackle insecurity, economic malaise and widening poverty. (Photo by John Wessels/AFP Photo)

Floating on clear deep water and reflections near the cave entrance. Visitors can either bring their own kayaks or rent boats from the local community to paddle deep inside the cave and marvel at its wonders on March 2015 at Tham Khoun Ex, Laos. Tham Khoun Xe, commonly known as the Xe Bang Fai River Cave, in Laos, has over 15km of passages filled with awe-inspiring views and wide expanses of water. Photographer, John Spies, 59, captured scenes from the entrances of the huge underground river passages, intricate cave formations and views from a passage high above the water. The cave is formed by the Xe Bang Fai river, a major tributary of the Mekong and in the dry season can be traversed using inflatable kayaks. (Photo by John Spies/Barcroft Media/ABACAPress)

“The Queen” painted fibreglass by artist John Humphreys is displayed backdropped by other works which feature in this year's Summer Exhibition on it's 250th year at the Royal Academy of Arts in London, Tuesday, June 5, 2018. The Summer Exhibition has been held since 1769, with around 1300 works on display this year and most of them available for purchase. It runs from June 12 until August 19. (Photo by Matt Dunham/AP Photo)

A man selling bags of water is seen at a taxi parking bay lined with campaign posters in the district of Lingwala in Kinshasa on December 18, 2018. Democratic Republic of Congo goes to the polls on December 23, 2018 in elections which could see the country emerge from 17 years of conflict-ridden rule under controversial President Joseph Kabila. (Photo by John Wessels/AFP Photo)

Devotees wear costumes made of banana leaves as they head to church to attend mass as part of a religious festival, in honor of St. John the Baptist, also known locally as the “mud people” festival, in Aliaga town, Nueva Ecija province, north of Manila, on June 24, 2017. Farmers coated in mud paraded in Philippine villages on June 24 to mark one of the Catholic nation's most colourful religious festivals. (Photo by Noel Celis/AFP Photo)

Colorado Gov. John Hickenlooper shows off his socks--one with Democratic presidential candidate Bernie Sanders and the other with Republican candidate Donald Trump – before entering his former brewpub for a book signing event to mark the release of his autobiography Thursday, May 26, 2016, in Denver. Hickenlooper, who is term-limited, is doing book talk rounds this week, reviving speculation that he is positioning himself to join Hillary Clinton's presidential campaign ticket. (Photo by David Zalubowski/AP Photo)