Koprowski, a Polish by birth, became the first to show in 1950 that it was possible to vaccinate against polio, the crippling and sometimes fatal disease which has now been completely eradicated.
Koprowski's son Christopher said that his father liked the scientific recognition that his work got even though he was not as well-known as fellow researchers like Jonas Salk and Albert Sabin.
Christopher also said that his father had been sick for several months. He died at the home where he had been living since 1957.
Hilary Koprowski self-administered the live-virus oral vaccine he had developed before the clinical trial in 1950. He became the director of The Wistar Institute in Philadelphia from 1957 to 1991.It was under his leadership that the independent research institute developed a vaccine which had helped eradicating the disease in various parts of the world. It was also around this time when the institute developed a more effective vaccine for rabies.
Koprowski was a talented musician who taught piano during his days in Rio de Janeiro where he was a penniless immigrant. He later hooked up with a lab there before shifting to the US, his son said.