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)

An armoured vehicle surrounded by Chicago cops at the time of the American depression, 1933. (Photo by Rolls Press/Popperfoto/Getty Images)

A child dressed as a Roman centurion poses during a parade to mark the anniversary of the foundation of Rome in 753 BC, on April 23, 2017 in Rome. (Photo by Alberto Pizzoli/AFP Photo)

In this June 29, 2016 file photo, boats docked at Central Marine in Stuart, Fla., are surrounded by blue green algae. The 153-mile-long Indian River Lagoon has been plagued by harmful algae blooms. Water quality testing data analyzed by the AP showed the average phosphorous level – a byproduct of fertilizers and human waste that algae thrive on, rose nearly 75 percent between 2000 and 2016. (Photo by Greg Lovett/The Palm Beach Post via AP Photo)

U.S Army combat camera photographer Spc. Hilda Clayton took this photo July 2, 2013 that was released by the U.S. Army, that shows an Afghan soldier engulfed in flame as a mortar tube explodes during an Afghan National Army live-fire training exercise in Laghman Province, Afghanistan. The accident killed Clayton and four Afghan National Army soldiers. (Photo by Spc. Hilda Clayton/U.S. Army via AP Photo)

People take part in the in the 41st annual Gay and Lesbian Mardi Gras parade in Sydney, New South Wales, Australia, 02 March 2019. The 41st parade features almost 200 floats. (Photo by Steven Saphore/EPA/EFE)

Bangladeshi pedestrian cross a broken baily brideg on July 7, 2019 in Sylhet. Heavy vehicle movement was restricted in this bridge but when a cement bag loaded truck got into the bridge, Suddenly, it collapse. (Photo by AFP Photo/Stringer)

A demonstrator runs between burning tires during a curfew, two days after the nationwide anti-government protests turned violent, in Baghdad, Iraq on October 3, 2019. (Photo by Wissm al-Okili/Reuters)