In 1935 Maurice Brodie, a research assistant at New York University and William Hallock Park of the New York City Department of Health, attempted to produce a polio vaccine, procured from virus in ground up monkey spinal cords, and killed by formaldehyde. Brodie first tested the vaccine on himself and several of his assistants. He then gave the vaccine to three thousand children. Many developed allergic reactions, but none of the children developed an immunity to polio. During the late 1940s and early 1950s, a research group, headed by John Enders at the Boston Children's Hospital, successfully cultivated the poliovirus in human tissue. This significant breakthrough ultimately allowed for the development of the polio vaccines. Enders and his colleagues, Thomas H. Weller and Frederick C. Robbins, were recognized for their labors with the Nobel Prize in 1954.