The invention of the modern mumps vaccine is the stuff of medical textbook legend. In 1963, a star researcher at the pharmaceutical company Merck took a swab of his own daughter’s throat to begin cultivating a weakened form of the mumps virus. And just four years later, in record time, Merck licensed Mumpsvax as the world’s first effective vaccine against this common and contagious childhood illness.

But a closer look at the history of vaccines shows that this popular origin story overlooks the decades-long search for a mumps cure that began in earnest during World War II. And it overshadows the fact that during the 1940s and 1950s, researchers chasing vaccines for polio and measles made incremental breakthroughs in lab techniques that ultimately made swift development of the 1960s Mumpsvax possible.

At 1 a.m. on March 21, 1963, a five-year-old girl in Philadelphia woke her father, Dr. Maurice Hilleman, complaining of a sore throat. Hilleman, a prickly genius working at Merck, immediately diagnosed her with a case of the mumps, a generally harmless childhood illness for which there was no treatment, and sent her back to bed.

But Hilleman couldn’t go back to sleep—he had an idea. Another research lab had just licensed a measles vaccine based on a new technique for growing weakened forms of a live virus in chicken embryos. Maybe he could do the same thing for mumps. Hilleman rushed to Merck for sampling supplies, came back and swabbed his daughter’s throat, then drove the viral culture back to the lab.

The mumps vaccine Hilleman developed in 1967 from that late-night inspiration is still in use as part of the combination measles, mumps and rubella (MMR) vaccine given to infants the world over. In the United States alone, mumps used to infect 186,000 kids a year in the 1960s. Today, thanks to the vaccine, there are fewer than 1,000 mumps infections annually.

Perhaps the most charming part of Hilleman’s mumps vaccine story is that he named the strain of mumps virus used to make the vaccine after his young daughter, Jeryl Lynn. The same Jeryl Lynn strain is still used in mumps vaccine production today.

The captivating tale of Hilleman’s record-breaking development of the mumps vaccine has all of the elements of a mid-century American success story, but the cure for the mumps didn’t start that fateful night in 1963.

As far back as World War I, the U.S. military identified mumps as a real problem. Elena Conis is a historian of medicine and public health at the UC Berkeley Graduate School of Journalism and author of Vaccine Nation: America’s Changing Relationship with Immunization. She says that mumps is most debilitating in adult men, who often experience painful swelling of the testicles.

“When American troops came together in crowded army camps and barracks, if there was a case of mumps you’d have the whole camp in the infirmary for weeks on end,” says Conis.

During World War I, mumps was the leading cause of missed days of active duty for the US army in France and reached a total of 230,356 cases. By World War II, the threat from mumps and measles was serious enough that the military’s Office of Scientific Research and Development treated it as a national security issue.

One of the chief obstacles for developing a vaccine is growing large amounts of the target virus. In 1945, two American research teams made the simultaneous discovery that the mumps virus could be grown in chicken eggs, specifically “embryonic” eggs that had been fertilized.

Karl Habel at the U.S. Health Service used the egg technique to produce the very first experimental mumps vaccine in 1946. Habel’s vaccine was “inactivated,” meaning it contained no live mumps virus, just dead virus particles. The inactive mumps vaccine was tested on 2,825 West Indian workers at a Florida sugarcane plantation where mumps ran rampant, and it showed a 58 percent effectiveness against the virus.

The world had its first mumps vaccine, but by that time WWII was over and the urgency to find a mumps cure had passed.

“In the 1940s, the CDC hadn’t identified mumps among children as a top health priority,” says Conis. “After the war was over, illnesses like pneumonia and the flu were a much bigger concern. Parents didn’t like when their kids got mumps, but was considered an expected part of childhood.”

John Enders won a Nobel Prize in 1954 for his work cultivating the poliomyelitis virus that led to a long-awaited polio vaccine. Along with Habel, Enders is co-credited with discovering the embryonic chicken egg technique for growing viruses. And like Habel, Enders first experimented with the mumps virus before moving on to polio and eventually measles.

The polio vaccine was a game-changer, but it too was based on an inactivated or dead virus. To develop a measles vaccine, Enders figured out that if you pass the same virus through a chicken embryo over and over, it weakens over time. The result is an “attenuated” virus, an organism that’s way too weak to cause a full-blown infection in humans, but strong enough to trigger an immune response.

“It’s the development of polio vaccine in the 1950s that advances the techniques that make the development of the measles and then the mumps vaccine possible in the 1960s,” says Conis. “And Hilleman could never have developed the mumps vaccine if Enders hadn’t come up with the culturing techniques that he did.”

Hilleman deserves tremendous credit for a lifetime of groundbreaking vaccine work. Not only did he create a highly effective mumps vaccine using a live attentuated virus, but he improved on Enders’ measles vaccine and helped develop vaccines for rubella, hepatitis B and a viral form of liver cancer.

But when Mumpsvax was licensed in 1967, Conis says there was no market for a mumps vaccine. The public viewed childhood mumps as nothing more than a nuisance illness whose chief symptom was swollen, chipmunk-like facial glands. And some pediatricians felt it was best to be exposed to the mumps and acquire immunity naturally.

Hilleman’s mumps vaccine may have languished if Merck hadn’t combined it later with vaccines for the far more serious childhood illnesses of measles and rubella. The combination MMR vaccine was licensed in 1971 and provided a fast and inexpensive way to immunize large swaths of the population against multiple contagious childhood diseases at once.

The result was that by 1974, 40 percent of American children were immunized against the mumps as part of the MMR vaccine. And in 1977, the CDC’s Advisory Committee on Immunization Practice decided that while the mumps was still a low-priority disease, its inclusion in the MMR vaccine warranted mumps immunization for all children over 12 months.

When the CDC recommended a two-dose MMR regimen in 1998, cases of childhood mumps dipped to an all-time low of fewer than 400 cases a year.