The real reasons Jonas Salk didn’t patent the polio vaccine.

"There was near unanimity within the organization [National Foundation for Infantile Paralysis] that the public had already paid for the polio vaccine through their donations, and patenting it for profit would have represented double charging. That’s what Jonas Salk should have said to Murrow—not that all vaccines belong to the people, but rather that this vaccine belonged to the people....

There is an important footnote regarding Salk’s statement that “there is no patent.” Prior to Murrow’s interview with Salk, lawyers for the National Foundation for Infantile Paralysis did look into the possibility of patenting the vaccine, according to documents that Jane Smith uncovered during her dive into the organization’s archives. The attorneys concluded that the vaccine didn’t meet the novelty requirements for a patent, and the application would fail. This legal analysis is sometimes used to suggest that Salk was being somewhat dishonest—there was no patent only because he and the foundation couldn’t get one. That’s unfair. Before deciding to forgo a patent application, the organization had already committed to give the formulation and production processes for the vaccine to several pharmaceutical companies for free...."