The problem of mumps among soldiers quickly became apparent during the Second World War, too, as the infection once again began to spread through army camps. This time around, however, scientists had new information at hand: scientists in the 1930s had determined that mumps was caused by a virus and that it could, at least theoretically, be prevented through immunization. PHS surgeon Karl Habel noted that while civilians didn‘t have to worry about mumps, the fact that infection was a serious problem for the armed forces now justified the search for a vaccine. “To the military surgeon, mumps is no passing indisposition of benign course,” two Harvard epidemiologists concurred. Tipped off to the problem of mumps by a U.S. Army general and funded by the Office of Scientific Research and Development (OSRD), the source of federal support for military research at the time, a group of Harvard researchers began experiments to promote mumps virus immunity in macaque monkeys in the lab.
Within a few years, the Harvard researchers, led by biologist John Enders, had developed a diagnostic test using antigens from the monkey‘s salivary glands, as well as a rudimentary vaccine. In a subsequent set of experiments, conducted both by the Harvard group and by Habel at the National Institute of Health, vaccines containing weakened mumps virus were produced and tested in institutionalized children and plantation laborers in Florida, who had been brought from the West Indies to work on sugar plantations during the war. With men packed ten to a bunkhouse in the camps, mumps was rampant, pulling workers off the fields and sending them to the infirmary for weeks at a time. When PHS scientists injected the men with experimental vaccine, one man in 1,344 went into anaphylactic shock, but he recovered with a shot of adrenaline and “not a single day of work was lost,” reported Habel. To the researchers, the vaccine seemed safe and fairly effective—even though some of the vaccinated came down with the mumps. What remained, noted Enders, was for someone to continue experimenting until scientists had a strain infective enough to provoke a complete immune response while weak enough not to cause any signs or symptoms of the disease.
Those experiments would wait for well over a decade. Research on the mumps vaccine, urgent in wartime, became a casualty of shifting national priorities and the vagaries of government funding. As the war faded from memory, polio, a civilian concern, became the nation‘s number one medical priority. By the end of the 1940s, the Harvard group‘s research was being supported by the National Foundation for Infantile Paralysis, which was devoted to polio research, and no longer by OSRD. Enders stopped publishing on the mumps virus in 1949 and instead turned his full–time attention to the cultivation of polio virus. Habel, at the NIH, also began studying polio. With polio occupying multiple daily headlines throughout the 1950s, mumps lost its place on the nation‘s political and scientific agendas.