https://www.scientificamerican.com/article/paranoid-gossip-about-polio-vaccine/

“After several weeks of confusion about the safety of the new poliomyelitis vaccine, mass tests got underway last month. Walter Winchell had told his radio audience that the vaccine ‘may be a killer’ because one batch had been found with live virus. The National Foundation for Infantile Paralysis, which is conducting and financing the test, hastened to make clear that each batch of vaccine was subjected to a three-laboratory check. The foundation pointed out that Jonas Salk, who developed the vaccine, had given the commercial preparation to more than 4,000 Pittsburgh children, none of whom showed any untoward effects.”

—Scientific American, June 1954