Dr. Paul D. Parkman, whose research was instrumental in identifying the virus that causes rubella and developing a vaccine that has prevented an epidemic of the disease in the United States for more than 50 years, died on May 7 at his home in Auburn, N.Y., in the Finger Lakes region. He was 91.

The cause was lymphoblastic leukemia, his niece Theresa M. Leonardi said.

Rubella, also known as German measles because German scientists classified it in the 19th century, is a moderate illness for most patients, identified by a spotty and often itchy red rash. But in pregnancies, it can cause infants to be born with severe physical and mental impairments and can also cause miscarriages and stillbirths.

When Dr. Parkman was a pediatric medical resident in the 1950s at the State University Health Science Center (now the SUNY Upstate Medical University) in Syracuse, he once recalled, he anguished over showing a new mother her stillborn baby whose rash, he would learn later, probably resulted from the mother’s infection with rubella during pregnancy.

In 1964 and 1965, rubella — an epidemic that struck every six to nine years — caused about 11,000 pregnancies to be miscarried, 2,100 newborns to die and 20,000 infants to be born with birth defects.

That was the worst outbreak in three decades — and the last rubella epidemic in the United States. The disease was declared eliminated in the Americas in 2015, although the virus has not yet been eradicated in Africa or Southeast Asia.

The rubella virus was identified and isolated in the early 1960s by Dr. Parkman and his colleagues at the Walter Reed Army Institute of Research in Silver Spring, Md., and a team of researchers at Harvard University led by Thomas H. Weller.

In 1966, Dr. Parkman, Dr. Harry M. Meyer Jr. and their collaborators at the National Institutes of Health, including Maurice R. Hilleman, disclosed that they had perfected a vaccine to prevent rubella. Dr. Parkman and Dr. Meyer assigned their patents to the N.I.H. so that the vaccines could be manufactured, distributed and administered promptly.

“I never made a nickel from those patents because we wanted them to be freely available to everybody,” he said in an oral history interview for the N.I.H. in 2005.

President Lyndon B. Johnson thanked the researchers, noting that they were among the few who could “number themselves among those who directly and measurably advance human welfare, save precious lives, and bring new hope to the world.”

Still, after Dr. Parkman retired from the government in 1990, as director of the Food and Drug Administration’s Center for Biologics Evaluation and Research, he expressed concern about what he called the unfounded skepticism that persisted about the value of vaccines.

“With the exception of safe drinking water, vaccines have been the most successful medical interventions of the 20th century,” he wrote in 2002 in Food and Drug Administration Consumer, an agency journal.

“As I look back on my career, I have come to think that perhaps I was involved in the easy part,” he added. “It will be for others to take on the difficult task of maintaining the protections that we struggled to achieve. We must prevent the spread of this vaccine nihilism, for if it were to prevail, our successes could be lost.”

Paul Douglas Parkman was born on May 29, 1932, in Auburn and raised in Weedsport, a nearby village of about 1,200. His father, Stuart, was a postal clerk who served on the village Board of Education and raised poultry to support his son’s education. His mother, Mary (Klumpp) Parkman, managed the household.

In 1955, Paul married a former kindergarten classmate, Elmerina Leonardi. She is his only immediate survivor. His brother, Stuart, and his sister, Phyllis Parkman Thompson, died earlier.

Enrolled in an accelerated degree program, he received his bachelor’s degree in pre-medicine from St. Lawrence University in Canton. N.Y., and his medical degree from the State University Health Science Center, both in 1957.

In 1960, he enrolled in the Army Medical Corps as a captain. After serving at Walter Reed as a researcher, he was chief of general virology for the N.I.H. from 1963 until the department was absorbed by the Food and Drug Administration in 1972. There, as director of the biologics center, he oversaw policies on H.I.V./AIDS testing and the approval of a vaccine for the most common cause of bacterial meningitis and imposed greater scrutiny of blood banks. He retired in 1990 as director of the Center for Biologics Evaluation and Research.

Dr. Parkman was trained as a pediatrician. That he came to specialize in viruses was both serendipitous and inauspicious.

While stationed at Fort Dix in New Jersey, he was assigned to study the seasonal flood of head cold and flu cases among new recruits.

“A runny nose isn’t too much to look at,” Dr. Parkman said in the oral history interview. He became hooked on virology, but he returned to Washington hoping for a subject more challenging than the common cold. He found it.