Polio Vaccine's Efficacy Results Published Today (4/12) in 1955

That doesn't cover the emotional response of the announcement. Quoting from https://www.smithsonianmag.com/history/salk-sabin-and-the-ra... :

> On April 12, 1955, Dr. Thomas Francis Jr., who monitored the Salk trials, called a press conference at the University of Michigan. The conference was broadcast to to 54,000 physicians who gathered in movie theaters; millions of Americans tuned in by radio. After Francis declared Salk’s vaccine to be “safe and effective,” church bells rang out and tearful families embraced. The polio panic would soon be over, as pharmaceutical companies rushed to create hundreds of millions of doses of the new vaccine.