In contrast to medical wisdom in the 1960s and 1970s, Huebner was confident that viruses were a cause of cancer in humans and convinced the United States Department of Health, Education and Welfare to provide $60 million in grants to fund research on the connection as part of the War on Cancer. This led to the discovery of the role that cytomegalovirus plays in opportunistic infections in patients with immunodeficiency. Research on retroviruses led to the development of a vaccine for hepatitis B, which has led to major decreases in rates of liver cancer, rates of some viral cancers, like that of the liver, have been sharply reduced.