Maurice Ralph Hilleman (August 30, 1919 – April 11, 2005) was an American microbiologist. He specialized in vaccinology. He developed over 36 vaccines, more than any other scientist. Of the 14 vaccines currently recommended, he developed eight: those for measles, mumps, hepatitis A, hepatitis B, chickenpox, meningitis, pneumonia and "Haemophilus influenza" bacteria. He also played a role in the discovery of the cold-producing adenoviruses, the hepatitis viruses, and the cancer-causing virus SV40.