Professor and scientists Jonas Salk started studying the polio virus at the University of Pittsburg. He first started testing a vaccine on monkeys and found that they were successful in increasing antibodies for polio. In 1952 he conducted first limited field tests on children with positive results. Finally, in 1954 conducted his mass field trial testing both the Salk vaccine and a placebo vaccine on 1.3 million American schoolchildren. The tests were successful in reducing polio cases and the vaccines began production the year later.

Other notable events on February 23rd:

In 1945, Six US soldiers raise the American flag on the island of Iwo Jima during World War II.

In 1870, Mississippi is readmitted to the United States following the Civil War.

In 1822, Boston votes to become a city and is granted a charter.

Jonas Salk during his professional career US/France, Sanofi Pasteur Photo Archive – Copyright Sanofi Pasteur