I have no idea. What difference would that make. The evidence is clear and unequivocal as to its safety and efficacy. Have you had the polio vaccine?and when first time it was used in humans ? and how long C19 vaccine was tested for ?
On April 26, 1954, the Salk polio vaccine field trials, involving 1.8 million children, begin at the Franklin Sherman Elementary School in McLean, Virginia.
One year later, on April 12, 1955, researchers announced the vaccine was safe and effective and it quickly became a standard part of childhood immunizations in America.