Sencer was director of the Centers for Disease Control and Prevention from 1966 to 1977 and served as New York City's health commissioner during the AIDS crisis of the 1980s.
He coordinated the CDC's involvement in an international campaign to eradicate smallpox, a historically deadly scourge. The campaign was hugely successful — the last naturally occurring smallpox case was reported in the late 1970s. It also was one of the agency's first major steps into international public health, a field in which the CDC is now considered a leader.
But for most people, Sencer is most remembered for his involvement in the 1976 swine flu vaccination campaign.
Health officials became alarmed when a flu virus linked to swine was detected in soldiers at Ft. Dix, N.J., including one young man who died. It reminded them of the terrible Spanish flu pandemic that caused millions of deaths around the world in 1918 and 1919.
Sencer coordinated a series of high-level meetings and recommended to President Ford that a national vaccination campaign be launched to prevent widespread deaths and illnesses.
More than 40 million Americans were vaccinated, but the epidemic never materialized. Worse, the government began to receive dozens of reports of a paralyzing condition called Guillain-Barre syndrome that was blamed on the vaccine. The campaign was suspended in December of that year and Sencer lost his job.
Sencer also was in charge in 1976, when CDC investigators identified the bacteria behind an outbreak of strange lung infections at a Philadelphia convention of the American Legion. The condition would become known as Legionnaire's disease.
After leaving the CDC, Sencer took a variety of positions, including heading New York City's health department, considered one of the top jobs in U.S. public health.
In recent years, he remained an energetic and regular presence at the CDC. He was an advisor for the agency during the 2009 swine flu pandemic, and sometimes acted as a de facto CDC historian.
Sencer was born Nov. 10, 1924, in Grand Rapids, Mich., and received his medical degree from the University of Michigan and a master's degree in public health from Harvard University.
He is survived by his wife, Jane, and three children.