Maurice Ralph Hilleman developed vaccines at the Merck Institute of Therapeutic Research in West Point, Pennsylvania, during the twentieth century. Over the course of his career at Merck, Hilleman created over forty vaccines, making him one of the most prolific developers of vaccine in the twentieth century. Of the fourteen vaccines commonly given to children in the US by 2015, Hilleman was responsible for eight of them. Hilleman's most widely used vaccine was his measles, mumps, and rubella (MMR) vaccine. Hilleman's MMR vaccine prevented many diseases and also rubella in millions of children and pregnant women. Rubella in pregnant women often led to congenital rubella syndrome in the fetus, causing severe malformations.