Over the next several decades Lilly continued to develop and introduce new drugs to the marketplace. In the 1950s, Lilly introduced two new antibiotics: vancomycin and erythromycin. In addition Lilly was heavily involved in production and distribution of Jonas Salk's poliomyelitis (polio) vaccine. In 1954, the National Foundation for Infantile Paralysis (NFIP) contracted with five pharmaceutical companies to produce Salk's polio vaccine for clinical trials. These included Lilly as well as Parke, Davis and Company, Cutter Laboratories, Wyeth Laboratories, and Pitman-Moore Company. Lilly's selection to produce the vaccine was, in part, due to its previous experience in collaborations with university researchers. Lilly manufactured 60 percent of the Salk vaccine in 1955.