Susan Ellenberg started out as a high school math teacher—then became a leading biostatistician

A mathematical puzzle fascinated Susan Ellenberg as a child.

John is twice Mary’s age when John was Mary’s age. When Mary will be John’s age, the sum of their ages will be 63. How old are John and Mary?

Ellenberg occasionally chipped away at the question laid out by her father, a CPA, by randomly plugging in numbers. But soon, she discovered another way to approach it.

“When I got to high school algebra, I learned that there was an actual way to solve this problem. I was so excited I knew how to do it,” Ellenberg, emerita professor of biostatistics, medical ethics, and health policy at the University of Pennsylvania Perelman School of Medicine, said on the Cancer History Project podcast.

“With my algebra homework, I would often do more problems than were actually assigned because I just thought it was so cool that there was an actual way to do this and not just do trial and error and guess,” she said.

Ellenberg never intended to become a researcher, or even end up in statistics—a STEM field that has been welcoming to women for a long time.

“It wasn’t that way in mathematics, certainly. But in statistics, it was more friendly,” Ellenberg said.

This conversation is the first in a collection of interviews with women biostatisticians that will be available on the Cancer History Project.

Ellenberg wanted to be a teacher, but she struggled to decide what subject to specialize in. That changed after seeing her college entrance exam math scores—the highest in her graduating class, despite not having been in the honors math program.

“When I saw those scores, it was like a light bulb went on over my head,” Ellenberg said. “It was like, ‘Math! I could be a math teacher!’”

In the 1960s, Ellenberg attended Radcliffe College, then the women’s college associated with Harvard University, where she took coeducational math classes and quickly achieved her dream after graduating by teaching at a nearby high school.

After a year at that job, Ellenberg moved to a school in Maryland because her husband, Jonas, started a job at NIH. She taught there for two years, but then took a break to start a family.

But when Ellenberg was pregnant with her first child, her friend Janet Wittes—who had been graduate school classmates with Jonas Ellenberg—asked her for help with computer programming for a project for the eminent biostatistician Jerome Cornfield, then at George Washington University.

Ellenberg agreed to take the job.

She liked it enough to carry on after her baby was born. “Then, I thought, ‘Well, I had taken a couple of statistics courses in my background, and I’m working for statisticians now. I’m a math person, so maybe I should take another statistics course,’” Ellenberg said.

Ellenberg took an evening class at GW, and then another, until Jonas said, “If you’re going to take courses, you might as well be in a degree program.”

So, she enrolled in a doctoral program in mathematical statistics and continued working with Cornfield, who helped to train her in clinical trial design and analysis. Cornfield’s friends—fellow pioneers in statistics—including Nathan Mantel, Max Halperin, and Sam Greenhouse, the latter of whom became Ellenberg’s thesis advisor, frequently visited as well.

Ellenberg remembers Mantel peeking over her shoulder as she read an analysis of a clinical trial. He pointed out why the analysis was wrong, and suggested the correct way to approach it.

After eight years, in 1980, Ellenberg earned her PhD.

As she wrapped up her degree, Ellenberg moved to the nascent Emmes Clinical Research Organization, which had been contracted to be the statistical center for the Gastrointestinal Tumor Study Group. This became Ellenberg’s first experience with cancer and first time being the primary statistician on studies, where she worked alongside leading oncologists, including Charles Moertel and Robert Mayer (The Cancer Letter, July 8, 1994).

Ellenberg then transferred to NCI in 1982 to work with Richard Simon (The Cancer Letter, May 24, 2024). For six years, she primarily took part in the Cancer Therapy Evaluation Program and expanded her knowledge of cancer research.

But then, a job opportunity arose that Ellenberg couldn’t refuse: chief of the newly founded biostatistics branch of the Division of AIDS at the National Institute of Allergy and Infectious Diseases, or NIAID.

“Honestly, I could have worked my whole career at the National Cancer Institute—I really enjoyed it,” Ellenberg said. “But I felt like I couldn’t say no to this opportunity to work in this incredibly scary and new disease, bringing my experience in doing large-scale clinical trials to an infectious disease community that really had relatively little experience in these large-scale trials.”

Beginning in 1988, Ellenberg helped NIAID coordinate and design large-scale clinical trials to investigate azidothymidine, or AZT, in HIV-infected populations as well as compare AZT to other HIV/AIDS drugs. She also managed the Data and Safety Monitoring Board for the HIV/AIDS trials, and implemented closed sessions that shared interim data only with the DSMB and lead people within the NIAID Division of AIDS, but not with FDA or pharmaceutical companies.

“That was the origin of open and closed sessions for Data and Safety Monitoring Boards, which is the standard approach nowadays, but in those days, very unusual,” Ellenberg said.

Much of her time was also dedicated to working with AIDS activists. At the 1989 International AIDS Conference, Ellenberg picked up a brochure by the AIDS Coalition to Unleash Power, or ACT UP, describing how the members believed clinical trials could be improved.

“I was very excited to see this document. I thought, ‘These people should be our partners, not our enemies,’” Ellenberg said.

She began to organize informal meetings every three months where statisticians from institutions including NIH, Harvard, and FDA—and eventually, some clinicians—would meet with AIDS activists. Later, Ellenberg found out that NIAID director Anthony Fauci was having his own back-channel conversations with AIDS activists. He told the Division of AIDS director to allow activists to attend the formal AIDS Clinical Trials Group meetings.

“They were very productive. [The activists] had good ideas about how to run these studies in a better way, and many of their ideas were adopted,” Ellenberg said. “On the other hand, we were able to explain to them why some of their ideas really weren’t workable, and they listened because we were really having good, productive interaction.”

In 1993, Ellenberg joined FDA as the inaugural director of the Office of Biostatistics and Epidemiology in the Center for Biologics Evaluation and Research.

One of the big issues Ellenberg dealt with in that role was proponents of the anti-vaccination movement. Many people feared that the diphtheria-tetanus-pertussis vaccine caused sudden infant death syndrome, and that the measles-mumps-rubella vaccine caused autism.

People who believed that they or their children had been harmed by a vaccine could report it in the Vaccine Adverse Event Reporting System—a database that Ellenberg and her colleagues reviewed and published papers on.

“It certainly didn’t stop the anti-vaxxers,” Ellenberg said. “But what you hope it will do is prevent more rational people from becoming anti-vaxxers.”

In 2004, Ellenberg returned to her first career passion by moving to Penn’s Perelman School of Medicine, where she has remained for the past two decades.

“I said I would teach a class on clinical trials, which I did all the years until I became emeritus,” she said. “I really enjoyed doing that, [going] back to my original love of teaching.”