This virologist saved millions of children—and stopped a pandemic

In April 1957, a mysterious illness was making its way through Hong Kong. Medical workers encountered throngs of children with “glassy-eyed stares,” and more than 10 percent of the city’s population was infected with influenza. The scientific community stayed quiet, but American virologist Maurice Hilleman recognized the threat: A pandemic was brewing.

Hilleman thought the disease was a new strain of influenza capable of spreading around the world. By the time the virus arrived in the U.S. in fall 1957, he was ready with a vaccine. His work prevented millions from contracting the deadly virus—and that’s a small fraction of the people Hilleman would save over the course of his career.

Born in August 1919, at the height of the Spanish flu, Hilleman was raised on a farm near Miles City, Montana. During the Depression, he managed to get a job as an assistant manager at a J.C. Penney store and planned to spend the rest of his professional career with the company—until his older brother convinced him to apply to college. He went to Montana State University on a full scholarship, graduated first in his class in 1941—and was accepted to every graduate school he applied to.

As a doctoral student in microbiology at the University of Chicago, Hilleman proved that chlamydia was actually a bacteria instead of a virus, a discovery that helped doctors treat the disease. Against his professor’s wishes, Hilleman went into the pharmaceutical industry instead of academia because he believed he’d be better positioned there to bring the benefits of his research to patients.

By the end of his career, he would develop more than 40 vaccines that prevented disease and death throughout the world. (Here's how vaccines keep diseases at bay.)

Heading off a pandemic

After four years with the E.R. Squibb pharmaceutical company in New Jersey, Hilleman transferred to the Walter Reed Army Medical Research Institute in Washington, D.C., to study respiratory illnesses and influenza outbreaks. There he proved that influenza viruses undergo mutations that allow them to bypass antibodies previously developed to the strain. This explained why one influenza vaccine didn’t protect a person for life, as a smallpox or polio vaccine could.

Through this research, Hilleman became convinced that the virus in Hong Kong could be substantially different from existing strains, and thus could be deadly if it came to the United States or other nations. When he picked up a copy of The New York Times on April 17, 1957 and read about the situation in Hong Kong, he exclaimed, “My God. This is the pandemic. It’s here!” The next day he asked the military to collect virus samples there.

A month later, he received gargled saltwater from an ill Navy serviceman who had been to Hong Kong. Hilleman began incubating the virus and testing it against antibodies from hundreds of soldiers and civilians. He couldn’t find a single person with antibodies to this strain of influenza. (Meet the scientist who discovered the first coronavirus.)

Hilleman sent samples of the new virus to other research organizations, which confirmed that only a few elderly citizens who had survived the 1889-1890 influenza pandemic had any antibody resistance. That meant nearly everyone was at risk of catching the new strain.

“In 1957 we all missed it. The military missed it and the World Health Organization missed it,” Hilleman later said in an interview.

Realizing how little time the country had to prepare, Hilleman contacted pharmaceutical manufacturers directly and asked them to make a vaccine from his samples. He also demanded that roosters that would otherwise have been killed be kept alive to fertilize enough eggs to prepare the vaccine. Even though his work had not yet been reviewed by the main U.S. vaccine regulatory agency, the Division of Biological Standards, the pharmaceutical companies agreed. Because regulations now are far tighter this type of workaround would be impossible today.

Because of Hilleman’s perseverance, 40 million doses of the vaccine had been created by the time the flu hit American shores in fall 1957. Ultimately, the virus killed 1.1 million people worldwide and an estimated 116,000 people in the United States. But the U.S. surgeon general at the time, Leonard Burney, said the virus would have infected millions more Americans had there been no vaccine. The U.S. military awarded Hilleman a Distinguished Service Medal for his work.

“That’s the only time we ever averted a pandemic with a vaccine,” Hilleman recalled.

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All in the family

In March 1963, Hilleman’s five-year-old daughter, Jeryl Lynn, stumbled into his room in the middle of the night and complained about a sore throat and swollen jaw. She had contracted mumps.

Although rarely deadly, mumps can occasionally cause deafness and inflammation of the brain, pancreas, and testicles—sometimes leading to sterility in young men. In 1964, the U.S. had an estimated 210,000 mumps cases, according to the CDC.

Hilleman put his daughter to bed, then drove to his lab for materials to swab her throat. With her samples, he began growing the virus in solutions of dissolved, embryonic chickens to attenuate the disease, or make it less effective at infecting humans. By infecting batch after batch of chicken cells, the virus gradually became better at infecting chickens and worse at infecting humans. This way, Hilleman created a weakened virus that, when injected in humans, would be strong enough to create antibodies but not strong enough to give them the disease.

Jeryl Lynn’s younger sister Kirsten was one of the first to receive her father’s experimental vaccine in 1966. “Here was a baby being protected by a virus from her sister. This has been unique in the history of medicine, I think,” Hilleman later said in an interview with The Vaccine Makers project. Normally, younger children are infected by their older siblings, not given immunity.

One year later—and nearly four years after Jeryl Lynn woke up with a sore throat—Hilleman licensed his mumps vaccine. The weakened strain of virus from his daughter’s mouth is still the base of the mumps vaccine used around the world today. (Here’s why a coronavirus vaccine could take way longer than a year to develop.)

Out of the spotlight

Hilleman’s success was in part due to his position at Merck, the pharmaceutical company he worked at for 47 years. He was given direct control over his research there, and with Merck’s ample financial resources at their disposal, Hilleman and his team developed more than 40 vaccines for humans and animals. “There was money to spend to do what you needed to do [at Merck]. Money wasn’t an object. You could do your research,” Hilleman’s second wife Lorraine Witmer once told Hilleman’s biographer. By working in the private sector—the “dirty industry” as Hilleman joked—he was able to guide his research from the lab to the marketplace with his signature brashness.

The pharmaceutical industry had its drawbacks, though, and at times prevented Hilleman from gaining public recognition for his work. “I thought that if my name appeared on the paper, or if I was the one put in front of the television cameras or radio microphones, people would think that I was selling something,” Hilleman explained after his name was not included on the paper proving his hepatitis B vaccine was effective. In the end, Hilleman didn’t name a single discovery after himself.

Hilleman and his team developed eight of the 14 vaccines currently recommended for children: measles, mumps, hepatitis A, hepatitis B, chickenpox, meningitis, pneumonia, and Haemophilus influenzae (Hib vaccine). The WHO estimates that the measles vaccine alone prevented 20.3 million deaths worldwide between 2000 and 2015.

In 1998, researcher A.J. Wakefield published an article claiming that Hilleman’s mumps, measles, and rubella (MMR) vaccine caused autism. This study sparked an anti-vaccination movement, even though the paper was disproven by several independent studies and formally retracted by the journal in 2010—five years after Hilleman had died from cancer at age 85.

At the time of Hilleman’s death, scientists in the field credited him with likely saving more people than any other scientist in the 20^th century. “The scientific quality and quantity of what he did was amazing,” Dr. Anthony Fauci told The New York Times in 2005. “Just one of his accomplishments would be enough to have made for a great scientific career.”