WASHINGTON - Irving Millman, a microbiologist who played an instrumental role in developing the hepatitis B vaccine, one of the most important medical advances of the latter 20th century and one that has saved millions of lives, died April 17 in Washington, D.C. He was 88.

The cause was complications from internal bleeding, said his daughter Diane.

Hepatitis B is an infectious virus that can lead to chronic liver disease, cirrhosis, and a deadly form of cancer. More than 1 billion people worldwide have received the vaccine since it became commercially available in 1982.

Because of the protection it provides against liver cancer, it has been called the first “cancer vaccine.’’

In the late 1960s and early ’70s, Dr. Millman was the only trained immunologist on an eclectic team of hepatitis researchers at the Fox Chase Cancer Center in Philadelphia. Leading the team was scientist Baruch Blumberg, a future Nobel laureate.

Part biochemist and part anthropologist, Blumberg had spent the previous decade collecting blood samples from populations around the world for the study of infectious disease. Using the serum from an Australian aborigine, he had identified the hepatitis B virus. He received the 1976 Nobel Prize in Medicine for that work, and died last year at 85.

Once Blumberg had isolated the virus, the challenge was to halt its transmission from one person to another. Dr. Millman’s arrival at the Fox Chase laboratory in 1967, Blumberg wrote in an essay, was “perhaps the most important factor’’ in making the breakthrough discovery.

Without Dr. Millman, Blumberg told the Jewish Exponent in 1993, “we couldn’t have made that vaccine, no question about it.’’

Dr. Millman launched his career at Northwestern University in Evanston, Ill., where he did research on a tuberculosis vaccine in the 1950s.

He later joined the Merck pharmaceutical company, where he worked on vaccines for whooping cough and rubella.